abdomen

The part of the body of a vertebrate containing the digestive organs.

abdominopelvic cavity

Division of the anterior (ventral) cavity that houses the abdominal and pelvic viscera.

abducens

Sixth cranial nerve; responsible for contraction of one of the extraocular muscles.

abduction

Movement in the coronal plane that moves a limb laterally away from the body; spreading of the fingers.

accommodation

(In vision) changes in lens shape to affect refraction of incoming light rays.

acetabulum

Large, cup-shaped cavity located on the lateral side of the hip bone; formed by the junction of the ilium, pubis, and ischium portions of the hip bone.

acetylcholine

An important neurotransmitter.

actin

Protein that makes up most of the thin myofilaments in a sarcomere muscle fibre.

action potential

Change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibres.

active transport

Form of transport across the cell membrane that requires input of cellular energy.

adduction

Movement in the coronal plane that moves a limb medially toward or across the midline of the body; bringing fingers together.

adenosine diphosphate (ADP)

Lower energy form of ATP, containing two phosphate groups after the third phosphate group phosphorylated another molecule and transferring energy to it.

adenosine triphosphate (ATP)

Nucleotide containing ribose and an adenine base that is essential in energy transfer.

adipocyte

Lipid storage cells.

adipose tissue

Specialized areolar tissue rich in stored fat.

adrenal gland

Endocrine glands located at the top of each kidney that are important for the regulation of the stress response, blood pressure and blood volume, water homeostasis, and electrolyte levels.

adrenal medulla

Inner layer of the adrenal glands that plays an important role in the stress response by producing epinephrine and norepinephrine.

adrenergic

Synapse where norepinephrine is released, which binds to α- or β-adrenergic receptors.

agonist

(Also, prime mover) muscle whose contraction is responsible for producing a particular motion.

albumin

a globular serum protein primarily involved in transport.

alkaline

An ionic solution with basic properties (pH >7).

alpha chain

A polypeptide component of the hemoglobin protein containing 141 amino acids.

amacrine cell

Type of cell in the retina that connects to the bipolar cells near the outer synaptic layer and provides the basis for early image processing within the retina.

amino

Chemical functional group NH2, a component of amino acids.

amino acid

Building block of proteins; characterized by an amino and carboxyl functional groups and a variable side-chain.

amphiarthrosis

Slightly mobile joint.

amphipathic

Molecule that contains both hydrophilic and hydrophobic regions.

ampulla

In the ear, the structure at the base of a semicircular canal that contains the hair cells and cupula for transduction of rotational movement of the head.

amylopectin

a branched-chain polymer of D-glucose units.

amylose

A straight-chain polymer of D-glucose units.

anabolic reaction

Reactions that build smaller molecules into larger molecules.

anion

Atom with a negative charge.

antagonist

Muscle that opposes the action of an agonist.

antagonistic

Muscle that opposes the action of an agonist.

antebrachial

Relating to the forearm.

antebrachium

Lower arm, between elbow and wrist.

anterior

Describes the front or direction toward the front of the body; also referred to as ventral.

anterior cavity

See ventral cavity

anterior horn

Gray matter of the spinal cord containing multipolar motor neurons, sometimes referred to as the ventral horn.

antibody

(Also, immunoglobulin) antigen-specific protein secreted by plasma cells.

aorta

Largest artery in the body, originating from the left ventricle and descending to the abdominal region where it bifurcates into the common iliac arteries at the level of the fourth lumbar vertebra; arteries originating from the aorta distribute blood to virtually all tissues of the body.

apical

That part of a cell or tissue, which, in general, faces an open space.

apocrine sweat gland

Type of sweat gland that is associated with hair follicles in the armpits and genital regions.

apoptosis

Programmed cell death.

appendicular skeleton

All bones of the upper and lower limbs, plus the girdle bones that attach each limb to the axial skeleton.

aqueous humour

Watery fluid that fills the anterior chamber containing the cornea, iris, ciliary body, and lens of the eye.

arachnoid granulation

Outpocket of the arachnoid membrane into the dural sinuses that allows for reabsorption of CSF into the blood.

arachnoid mater

Middle layer of the meninges named for the spider-web–like trabeculae that extend between it and the pia mater.

arachnoid trabeculae

Filaments between the arachnoid and pia mater within the subarachnoid space.

areolar connective tissue

A type of connective tissue proper that shows little specialization with cells dispersed in the matrix.

arrector pili

Smooth muscle that is activated in response to external stimuli that pull on hair follicles and make the hair “stand up.”

articular capsule

Connective tissue structure that encloses the joint cavity of a synovial joint.

articular cartilage

Thin layer of cartilage covering an epiphysis; reduces friction and acts as a shock absorber.

articular disc

Meniscus; a fibrocartilage structure found between the bones of some synovial joints; provides padding or smooths movements between the bones; strongly unites the bones together.

ascending tract

Central nervous system fibers carrying sensory information from the spinal cord or periphery to the brain.

atlas

First cervical (C1) vertebra.

atom

The smallest unit of an element that retains the unique properties of that element.

atomic number

Number of protons in the nucleus of an atom.

auricle

Fleshy external structure of the ear.

autonomic nervous system

Functional division of the nervous system that is responsible for homeostatic reflexes that coordinate control of cardiac and smooth muscle, as well as glandular tissue.

autorhythmicity

Ability to depolarize without prior nervous stimulation. This ability is a characteristic of cardiac muscle cells.

avascular

Lacking blood vessels.

axial skeleton

Central, vertical axis of the body, including the skull, vertebral column, and thoracic cage.

axis

Second cervical (C2) vertebra.

axon

Single process of the neuron that carries an electrical signal (action potential) away from the cell body toward a target cell.

axon hillock

Tapering of the neuron cell body that gives rise to the axon.

axon segment

Single stretch of the axon insulated by myelin and bounded by nodes of Ranvier at either end (except for the first, which is after the initial segment, and the last, which is followed by the axon terminal).

axon segments

Single stretch of the axon insulated by myelin and bounded by nodes of Ranvier at either end (except for the first, which is after the initial segment, and the last, which is followed by the axon terminal).

axon terminal

End of the axon, where there are usually several branches extending toward the target cell.

azygous vein

Originates in the lumbar region and passes through the diaphragm into the thoracic cavity on the right side of the vertebral column; drains blood from the intercostal veins, esophageal veins, bronchial veins, and other veins draining the mediastinal region; leads to the superior vena cava.

ball-and-socket joint

Synovial joint at which the rounded portion of a bone rotates within a ring formed by a ligament and an articulating bone; functionally classified as uniaxial joint.

basal

That part of a tissue close to underlying body structures.

basal cell

Type of stem cell found in the stratum basale and in the hair matrix that continually undergoes cell division, producing the keratinocytes of the epidermis.

basal lamina

Thin extracellular layer that lies underneath epithelial cells and separates them from other tissues.

basal nuclei

Nuclei of the cerebrum (with a few components in the upper brain stem and diencephalon) that are responsible for assessing cortical movement commands and comparing them with the general state of the individual through broad modulatory activity of dopamine neurons; largely related to motor functions, as evidenced through the symptoms of Parkinson’s and Huntington’s diseases.

basement membrane

In epithelial tissue, a thin layer of fibrous material that anchors the epithelial tissue to the underlying connective tissue; made up of the basal lamina and reticular lamina.

basilar membrane

In the ear, the floor of the cochlear duct on which the organ of Corti sits.

beta chain

a polypeptide component of the hemoglobin protein containing 146 amino acids.

biaxial joint

Type of diarthrosis; a joint that allows for movements within two planes (two axes).

biceps brachii

Two-headed muscle that crosses the shoulder and elbow joints to flex the forearm while assisting in supinating it and flexing the arm at the shoulder.

biceps femoris

One of the hamstring muscles.

bile

Alkaline solution produced by the liver and important for the emulsification of lipids.

bipolar cell

Cell type in the retina that connects the photoreceptors to the ganglion cells.

body (of a vertebra)

anterior portion of each vertebra that supports the body weight.

body (of a vertebrae)

(Also, centrum) the anterior portion of each vertebra that supports the body weight.

brachioradialis

Muscle that can flex the forearm quickly or help lift a load slowly.

brachium

Upper arm, between shoulder and elbow.

brevis

Short

Brodmann's areas

Mapping of regions of the cerebral cortex based on microscopic anatomy that relates specific areas to functional differences, as described by Brodmann in the early 1900s.

buffer

A chemical system that resists change in pH of a solution by either accepting or releasing hydrogen ions in response to acids or bases, respectively.

bulbous corpuscle

(Also, Ruffini corpuscle) cutaneous receptors sensitive to skin stretch and sustained pressure.

bursa

Connective tissue sac containing lubricating fluid that prevents friction between adjacent structures, such as skin and bone, tendons and bone, or between muscles.

caecum

Beginning of the large intestine, forming a small pouch.

calcaneus

Heel bone; posterior, inferior tarsal bone that forms the heel of the foot.

canaliculi

(Singular = canaliculus) channels within the bone matrix that house one of an osteocyte’s many cytoplasmic extensions that it uses to communicate and receive nutrients.

cancellous bone

See spongy bone

capillary

Smallest of the blood vessels where physical exchange occurs between the blood and tissue cells surrounded by interstitial fluid.

carbohydrate

Class of organic compounds built from sugars, molecules containing carbon, hydrogen, and oxygen in a 1-2-1 ratio.

carboxyl (COOH)

Chemical functional group consisting of COOH, an important part of organic acids.

cardiac muscle

Heart muscle, under involuntary control, composed of striated cells that attach to form fibres, each cell contains a single nucleus, contracts autonomously.

carotid sinus

One of a pair of small pockets near the base of the internal carotid arteries that are the locations of the baroreceptors and chemoreceptors that trigger a reflex that aids in the regulation of vascular homeostasis

carpal

One of the eight small bones that form the wrist and base of the hand; these are grouped as a proximal row consisting of (from lateral to medial) the scaphoid, lunate, triquetrum, and pisiform bones, and a distal row containing (from lateral to medial) the trapezium, trapezoid, capitate, and hamate bones.

carrier protein

Membrane-spanning protein that binds to substances it needs to transport, changes shape, and moves the substance into or out of the cell (a form of facilitated diffusion or active transport pumps when energy is required).

carrier-mediated facilitated diffusion

Facilitated diffusion mechanism that utilizes a carrier protein that changes shape during the transport process.

cartilage

Semi-rigid connective tissue found on the skeleton in areas where flexibility and smooth surfaces support movement.

cartilaginous joint

Joint at which the bones are united by hyaline cartilage (synchondrosis) or fibrocartilage (symphysis).

catabolism

Chemical reaction that breaks down more complex organic molecules.

cation

Ion with a positive charge.

caudal

See inferior

cell cycle

Life cycle of a single cell, from its birth until its division into two new daughter cells.

cell differentiation

Process by which unspecialized cells become more specialized in structure and function.

cellular respiration

Production of ATP from glucose oxidation via glycolysis, the Krebs cycle, and oxidative phosphorylation.

Cellulose

An insoluble polysaccharide consisting of glucose chains that is the primary component of plant cell walls.

central

(In anatomy) describes a position toward the middle (center) of a structure or organ system.

central canal

(Also Haversian canal) longitudinal channel in the center of each osteon; contains blood vessels, nerves, and lymphatic vessels.

central neuron

Specifically referring to the cell body of a neuron in the autonomic system that is located in the central nervous system, specifically the lateral horn of the spinal cord or a brain stem nucleus.

cerebellum

Region of the adult brain connected primarily to the pons that developed from the metencephalon (along with the pons) and is largely responsible for comparing information from the cerebrum with sensory feedback from the periphery through the spinal cord.

cerebral aqueduct

Connection of the ventricular system between the third and fourth ventricles located in the midbrain.

cerebral cortex

Outer gray matter covering the forebrain, marked by wrinkles and folds known as gyri and sulci.

cerebral hemisphere

One half of the bilaterally symmetrical cerebrum.

cerebrospinal fluid (CSF)

Circulatory medium within the CNS that is produced by ependymal cells in the choroid plexus filtering the blood.

cerebrum

Region of the adult brain that develops from the telencephalon and is responsible for higher neurological functions such as memory, emotion, and consciousness.

ceruminous gland

Wax producing gland in the ear canal.

cervical

Neck

cervical vertebrae

Seven vertebrae numbered as C1–C7 that are located in the neck region of the vertebral column.

channel protein

Membrane-spanning protein that has an inner pore, which allows the passage of one or more substances (a form of facilitated diffusion).

channel-mediated facilitated diffusion

Facilitated diffusion mechanism that utilizes a channel protein that has a pore, which only allows certain substances to pass through.

chemoreceptor

Sensory receptor cell that is sensitive to chemical stimuli, such as in taste, smell, or pain.

cholesterol

Chemically, a type of steroid, cholesterol is a component of cell membranes and a precursor of some important vitamins and hormones.

cholinergic

Synapse at which acetylcholine is released and binds to the nicotinic or muscarinic receptor.

chondroblast

Cell responsible for forming new cartilage.

chondrocyte

cartilage cells

choroid

Highly vascular tissue in the wall of the eye that supplies the outer retina with blood.

choroid plexus

Specialized structures containing ependymal cells lining blood capillaries that filter blood to produce CSF in the four ventricles of the brain.

chromatin

Substance consisting of DNA and associated proteins.

chromosome

A long DNA molecule, combined with proteins that contains a number of genes. The normal chromosome complement is 23 pairs of homologous chromosomes, one each from mother and father.

cilia

Small appendage on certain cells formed by microtubules and modified for movement of materials across the cellular surface (singular = cilium).

ciliary body

Smooth muscle structure on the interior surface of the iris that controls the shape of the lens through the zonule fibres

circumduction

Circular motion of the arm, thigh, hand, thumb, or finger that is produced by the sequential combination of flexion, abduction, extension, and adduction.

clavicle

Collarbone; elongated bone that articulates with the manubrium of the sternum medially and the acromion of the scapula laterally.

clotting factor

(Also, coagulation factors) group of 12 identified substances active in coagulation.

coagulation factor

See clotting factor.

coccyx

Lowest part of the vertebral column; 'tailbone'

cochlea

Auditory portion of the inner ear containing structures to transduce sound stimuli.

cochlear duct

(Also scala media) space within the auditory portion of the inner ear that contains the organ of Corti and is adjacent to the scala tympani and scala vestibuli on either side.

collagen

The most abundant of three protein fibres found in the extracellular matrix of connective tissues.

colon

Portion of the large intestine.

compact bone

Dense osseous tissue that can withstand compressive forces.

complement proteins

a family of proteins that function to opsonize pathogens and promote the inflammatory response.

compound

A substance composed of two or more different elements joined by chemical bonds.

concave

Hollowed or rounded inward, like the inside of a bowl. Opposite of convex.

concentration gradient

Difference in the concentration of a substance between two regions.

condyloid joint

Synovial joint in which the shallow depression at the end of one bone receives a rounded end from a second bone or a rounded structure formed by two bones; found at the metacarpophalangeal joints of the fingers or the radiocarpal joint of the wrist; functionally classified as a biaxial joint.

cone

One of the two types of receptor cells in the retina that is specialized for color vision through the use of three photopigments distributed through three separate populations of cells.

connective tissue

Type of tissue that serves to hold in place, connect, and integrate the body’s organs and systems.

connective tissue proper

Connective tissue containing a viscous matrix, fibers, and cells.

continuous conduction

Slow propagation of an action potential along an unmyelinated axon owing to voltage-gated Na+ channels located along the entire length of the cell membrane.

contractility

Ability to shorten (contract) forcibly.

contralateral

Opposite side of the body.

control centre

Compares values to their normal range; deviations cause the activation of an effector.

convex

Having an outline or surface curved like the outside of a circle or sphere.

coracobrachialis

Muscle that abducts the arm.

cornea

Fibrous covering of the anterior region of the eye that is transparent so that light can pass through it.

coronal plane

See frontal plane

costal cartilage

Hyaline cartilage structure attached to the anterior end of each rib that provides for either direct or indirect attachment of most ribs to the sternum.

Cotransport

Form of secondary active transport in which two substances are moving in the same direction, with one substance providing energy for the other.

Countertransport

Secondary active transport mechanism in which two substances are moving in opposite directions, with one substance providing energy to pump the other substance.

covalent bond

Chemical bond in which two atoms share electrons, thereby completing their valence shells.

cranial

Referring to the head. Also see superior.

cranial cavity

Division of the posterior (dorsal) cavity that houses the brain.

cranial nerve

One of twelve nerves connected to the brain that are responsible for sensory or motor functions of the head and neck.

craniosacral system

Alternate name for the parasympathetic division of the autonomic nervous system that is based on the anatomical location of central neurons in brain-stem nuclei and the lateral horn of the sacral spinal cord; also referred to as craniosacral outflow.

crista ampullaris

Sense organ that responds to rotational movement (dynamic equilibrium), contained in each ampulla.

crus

The portion of the lower limb between the knee and the ankle.

cupula

Specialized structure within the base of a semicircular canal that bends the stereocilia of hair cells when the head rotates by way of the relative movement of the enclosed fluid.

cutaneous

Skin.

cytoplasm

Internal material between the cell membrane and nucleus of a cell, mainly consisting of a water-based fluid called cytosol, within which are all the other organelles and cellular solute and suspended materials.

cytosol

Clear, semi-fluid medium of the cytoplasm, made up mostly of water.

decussate

Cross or intersect like an 'X.'

deep

(In anatomy) describes a position farther from the surface of the body.

dehydration synthesis

Chemical reaction in which reactants combine to form a new compound, with one reactant giving up an atom of hydrogen and another reactant giving up a hydroxyl group (OH).

deltoid

Shoulder muscle that abducts the arm as well as flexes and medially rotates it and extends and laterally rotates it.

dendrite

One of many branchlike processes that extends from the neuron cell body and functions as a contact for incoming signals (synapses) from other neurons or sensory cells.

dendritic cell

A monocyte-derived phagocytic cell, functions as antigen-presenting cells in the immune system.

dens

Bony projection (odontoid process) that extends upward from the body of the C2 (axis) vertebra.

density

Mass per unit volume.

deoxyribonucleic acid (DNA)

Deoxyribose-containing nucleic acid that stores genetic information.

depolarization

Change in a cell membrane potential from rest toward zero.

depression

Downward (inferior) motion of the scapula or mandible.

dermal papilla

(Plural = dermal papillae) extension of the papillary layer of the dermis that increases surface contact between the epidermis and dermis.

dermis

Layer of skin between the epidermis and hypodermis, composed mainly of connective tissue and containing blood vessels, hair follicles, sweat glands, and other structures.

descending tract

Central nervous system fibers carrying motor commands from the brain to the spinal cord or periphery.

desmosome

A type of anchoring junction found between adjacent epithelial cells.

diaphragm

Skeletal muscle that separates the thoracic and abdominal cavities and is dome-shaped at rest.

diaphysis

Tubular shaft that runs between the proximal and distal ends of a long bone.

diarthrosis

Freely mobile joint.

diencephalon

Region of the adult brain that retains its name from embryonic development and includes the thalamus and hypothalamus.

diffusion

Movement of a substance from an area of higher concentration to one of lower concentration.

digit

Finger or toe.

digits

The fingers or toes.

diglyceride

A glycerol molecule with two fatty acid chains attached.

dilation

Becoming wider, larger, or more open.

diploë

Layer of spongy bone that is sandwiched between two the layers of compact bone found in flat bones.

dipole

Molecule with a negatively charged portion separated from a positively charged portion.

disaccharide

Molecule formed of a pair of monosaccharides; important to human physiology are sucrose, lactose, and maltose.

dissipate

Scatter or break up.

distal

Describes a position in a limb that is farther from the point of attachment or the trunk of the body.

dorsal

See posterior

dorsal cavity

Posterior body cavity that houses the brain and spinal cord; also referred to the posterior body cavity.

dorsal root ganglion

Sensory ganglion attached to the posterior nerve root of a spinal nerve.

dorsiflexion

Movement at the ankle that brings the top of the foot toward the anterior leg.

dura mater

Tough, fibrous, outer layer of the meninges that is attached to the inner surface of the cranium and vertebral column and surrounds the entire CNS.

dural sinus

Any of the venous structures surrounding the brain, enclosed within the dura mater, which drain blood from the CNS to the common venous return of the jugular veins.

dynamic equilibrium

Modality of equilibrium relating to rotational movement of the head.

dystrophin

A cell membrane-stabilizing protein that functions to prevent contraction-induced damage to muscle cells.

ear ossicle

One of three small bones located in the middle ear cavity that serve to transmit sound vibrations to the inner ear.

eccrine sweat gland

Type of sweat gland that is common throughout the skin surface; it produces a hypotonic sweat for thermoregulation.

effector

Organ that can cause a change in a value.

effort

The pulling or pushing force applied to a lever; in lever system in the body, the effort is a muscle with force applied at the insertion.

effort arm

Distance measured from the fulcrum to the effort (e.g., muscle insertion).

elastic cartilage

Type of cartilage, with elastin as the major protein, characterized by rigid support as well as elasticity.

elastic fibre

Fibrous protein within connective tissue that contains a high percentage of the protein elastin that allows the fibers to stretch and return to original size.

elasticity

Ability to stretch and rebound.

elastin

One of three protein fibres found in connective tissues.

Electrical Gradient

A difference in electrical charge across a space.

electrocardiogram (ECG or EKG)

Surface recording of the electrical activity of the heart that can be used for diagnosis of irregular heart function.

electrolyte

A solution containing ions; sometimes referring to ions themselves.

electron

A subatomic particle having a negative charge and nearly no mass; found orbiting the atom’s nucleus.

electron shell

Area of space a given distance from an atom’s nucleus in which electrons are grouped.

electronegative

The tendency of an atom to attract electrons in a covalent bond.

eleiden

Clear protein-bound lipid found in the stratum lucidum that is derived from keratohyalin and helps to prevent water loss.

element

A substance that cannot be created or broken down by ordinary chemical means.

elevation

Upward (superior) motion of the scapula or mandible.

ellipsoid joint

See condyloid joint

embryo

Developing human during weeks 3–8.

emulsify

Process of forming an emulsion.

emulsion

Combination of two or more unmixable liquids where one liquid contains a dispersion of the other liquids (often as tiny droplets).

encapsulated ending

Configuration of a sensory receptor neuron with dendrites surrounded by specialized structures to aid in transduction of a particular type of sensation, such as the lamellated corpuscles in the deep dermis and subcutaneous tissue.

endochondral ossification

Process in which bone forms by replacing hyaline cartilage.

endocrine

Tissue or organ that secretes hormones into the blood and lymph without ducts such that they may be transported to organs distant from the site of secretion.

endocytosis

Import of material into the cell by formation of a membrane-bound vesicle.

endolymph

Extracellular fluid of the inner ear, lying within the membranous labyrinth.

endomembrane system

Set of cellular organelles that often work together to produce, package, and export certain products.

endomysium

Loose and well-hydrated connective tissue covering each muscle fibre in a skeletal muscle.

endoplasmic reticulum (ER)

Cellular organelle that consists of interconnected membrane-bound tubules, which may or may not be associated with ribosomes (rough type or smooth type, respectively).

endosteum

Delicate membranous lining of a bone’s medullary cavity.

endothelium

Layer of smooth, simple squamous epithelium that lines the endocardium and blood vessels.

enteric nervous system

Neural tissue associated with the digestive system that is responsible for nervous control through autonomic connections.

enzyme

Molecule (usually a protein) that catalyzes chemical reactions.

ependymal cell

Glial cell type that filters blood at the choroid plexus.

epidermis

outermost tissue layer of the skin

epigastric region

Abdominopelvic region located in the central superior area below the xiphoid process.

epimysium

Loose and well-hydrated connective tissue covering each muscle fiber in a skeletal muscle.

epinephrine

Signaling molecule released from the adrenal medulla into the bloodstream as part of the sympathetic response.

epiphyseal line

completely ossified remnant of the epiphyseal plate

epiphyseal plate

(Also, growth plate) sheet of hyaline cartilage in the metaphysis of an immature bone; replaced by bone tissue as the organ grows in length.

epiphysis

Wide section at each end of a long bone; filled with spongy bone and red marrow.

epithalamus

Region of the diencephalon containing the pineal gland.

epithelial

Type of tissue that serves primarily as a covering or lining of body parts, protecting the body; it also functions in absorption, transport, and secretion.

erector spinae group

Large muscle mass of the back; primary extensor of the vertebral column.

erythrocyte

Red blood cell.

erythrocytes

Red blood cells.

essential amino acids

Amino acids that are required by, but cannot be synthesized by, the human body. These amino acids must, therefore, be supplied by the diet.

ethmoid bone

Unpaired bone that forms the roof and upper, lateral walls of the nasal cavity, portions of the floor of the anterior cranial fossa and medial wall of orbit, and the upper portion of the nasal septum.

eukaryotic

One of two major divisions of living things (or their cells) that have membrane-bound nuclei and other organelles and can form large complex organisms (including all animals, plants, fungi). By contrast, bacteria are prokaryotic.

Eustachian tube

(Also pharyngotympanic tube) tube linking the pharynx and middle ear, important for equalizing air pressure in the middle ear.

eversion

Foot movement involving the intertarsal joints of the foot in which the bottom of the foot is turned laterally, away from the midline.

excitability

Ability to undergo neural stimulation.

exocytosis

Export of a substance out of a cell by formation of a membrane-bound vesicle.

extensibility

Ability to lengthen (extend).

extension

Movement that increases the angle of a joint.

external ear

Structures on the lateral surface of the head, including the auricle and the ear canal back to the tympanic membrane.

external intercostal

Superficial intercostal muscles that raise the rib cage.

external oblique

Superficial abdominal muscle with fascicles that extend inferiorly and medially.

exteroceptor

Sensory receptor that is positioned to interpret stimuli from the external environment, such as photoreceptors in the eye or somatosensory receptors in the skin.

extracellular fluid (ECF)

Fluid outside cells (plasma or interstitial fluid).

extraocular

One of six muscles originating out of the bones of the orbit and inserting into the surface of the eye, which are responsible for moving the eye.

facial bones

Fourteen bones that support the facial structures and form the upper and lower jaws and the hard palate.

facilitated diffusion

Diffusion of a substance with the aid of a membrane protein.

fallopian tube

See uterine tube

false ribs

Vertebrochondral ribs 8–12 whose costal cartilage either attaches indirectly to the sternum via the costal cartilage of the next higher rib or does not attach to the sternum at all.

fascicle

Bundle of muscle fibres within a skeletal muscle

fatty acid

Consisting of a carboxyl group (COOH) and an unbranched hydrocarbon chain. A non-polar component of all lipids.

femur

Thigh bone; the single bone of the thigh.

fetus

Developing human during the time from the end of the embryonic period (week 9) to birth.

fibroblast

Most abundant cell type in connective tissue, secretes protein fibers and matrix into the extracellular space.

fibrocartilage

Tough form of cartilage, made of thick bundles of collagen fibers embedded in chondroitin sulfate ground substance.

fibrocyte

Mature, less active form of a fibroblast.

fibrous connective tissue

Dense connective tissue (irregular or regular) consisting of a dense array of collagen and reticular fibres.

fibrous joint

Joint where the articulating areas of the adjacent bones are connected by fibrous connective tissue.

fibrous tunic

Outer layer of the eye primarily composed of connective tissue known as the sclera and cornea.

fibula

Thin, non-weight-bearing bone found on the lateral side of the leg.

fingerprints

A superficial ridge on the skin surface of fingertips that forms from the dermal papillae underlying the epidermis in this location.

first-class lever

A lever system in which the effort and resistance are applied on opposite sides of the fulcrum.

fixator

Synergist that assists an agonist by preventing or reducing movement at another joint, thereby stabilizing the origin of the agonist.

flexion

Movement that decreases the angle of a joint.

floating ribs

Vertebral ribs 11–12 that do not attach to the sternum or to the costal cartilage of another rib.

fontanelle

Expanded area of fibrous connective tissue that separates the braincase bones of the skull prior to birth and during the first year after birth.

foramen

General anatomical term for a hole or opening (usually in bone. Plural = foramina).

foramina

General anatomical term for a hole or opening (usually in bone. Plural = foramina).

fourth ventricle

The portion of the ventricular system that is in the region of the brain stem and opens into the subarachnoid space through the median and lateral apertures.

fovea

Exact center of the retina at which visual stimuli are focused for maximal acuity, where the retina is thinnest, at which there is nothing but photoreceptors.

free nerve ending

Configuration of a sensory receptor neuron with dendrites in the connective tissue of the organ, such as in the dermis of the skin, that are most often sensitive to chemical, thermal, and mechanical stimuli.

frontal bone

Unpaired bone that forms forehead, roof of orbit, and floor of anterior cranial fossa.

frontal plane

Two-dimensional, vertical plane that divides the body or organ into anterior and posterior portions.

fulcrum

The point around which a lever rotates.

functional group

Group of atoms linked by strong covalent bonds that tends to behave as a distinct unit in chemical reactions with other atoms.

G protein

Ubiquitous family of proteins that generally act as switches (turning on or off chemical processes) by transmitting signals from outside to inside cells.

gamete

Haploid reproductive cell (egg or sperm in humans) that contributes genetic material to form an offspring.

ganglion

Localized collection of neuron cell bodies in the peripheral nervous system.

ganglion cell

Neuron of the retina that projects along the second cranial nerve.

gastrocnemius

Most superficial muscle of the calf.

germ cell

Cell that gives rise to a gamete.

girdle

An encircling or confining structure; in anatomy, the pectoral or pelvic girdle.

glenohumeral joint

Shoulder joint; formed by the articulation between the glenoid cavity of the scapula and the head of the humerus.

glenoid cavity

(Also, glenoid fossa) shallow depression located on the lateral scapula, between the superior and lateral borders.

glenoid fossa

See glenoid cavity

glial cells

Supportive neural cells.

glossopharyngeal nerve

Ninth cranial nerve; responsible for contraction of muscles in the tongue and throat and for part of the sense of taste, as well as causing saliva production.

glucose

Monosaccharide commonly used as energy in the body (substrate for glycolysis).

gluteal group

Muscle group that extends, flexes, rotates, adducts, and abducts the femur.

gluteus maximus

Largest of the gluteus muscles that extends the femur.

gluteus medius

Muscle deep to the gluteus maximus that abducts the femur at the hip.

glycerol

Molecule that forms the 'backbone' of many lipids, including triglycerides.

glycocalyx

Coating of carbohydrate molecules that surrounds the cell membrane.

glycogen

Polysaccharide used as a storage form of glucose in the liver.

glycolipid

A molecule composed of carbohydrate and lipid components.

glycoprotein

Protein that has one or more carbohydrates attached.

glycoproteins

A protein with at least one sugar molecule attached to it.

Golgi apparatus

Cellular organelle formed by a series of flattened, membrane-bound sacs that functions in protein modification, tagging, packaging, and transport.

gomphosis

Type of fibrous joint in which the root of a tooth is anchored into its bony jaw socket by strong periodontal ligaments.

gracilis

Muscle that adducts the thigh and flexes the leg at the knee.

graded potential

Change in the membrane potential that varies in size, depending on the size of the stimulus that elicits it.

gray matter

Regions of the nervous system containing cell bodies of neurons with few or no myelinated axons; actually may be more pink or tan in color but called gray in contrast to white matter.

greater sciatic notch

Large, U-shaped indentation located on the posterior margin of the ilium, superior to the ischial spine.

ground substance

Fluid or semi-fluid portion of the matrix.

growth hormone (GH)

(Also, somatotropin) anterior pituitary hormone that promotes tissue building and influences nutrient metabolism.

gustatory receptor cell

Sensory cells in the taste bud that transduce the chemical stimuli of gustation.

gyrus

Ridge formed by convolutions on the surface of the cerebrum or cerebellum.

hair bulb

Structure at the base of the hair root that surrounds the dermal papilla.

hair cells

Mechanoreceptor cells found in the inner ear that transduce stimuli for the senses of hearing and balance.

hair follicle

Cavity or sac from which hair originates.

hair root

Part of hair that is below the epidermis anchored to the follicle.

hallux

Big toe

hamstring group

Three long muscles on the back of the upper leg.

Haversian canal

See central canal

Haversian system

See osteon

heat-shock proteins

A family of proteins that are produced in the cell as a result of an exposure to stressful conditions.

helicotrema

Tip of the cochlea where the scala vestibuli meets the scala tympani.

hematopoiesis

See hemopoeisis

hemoglobin

Oxygen-carrying protein in erythrocytes (red blood cells).

hemopoiesis

(Also, hematopoiesis) production of the formed elements of blood.

hindbrain

Posterior region of the adult brain that develops from the rhombencephalon and includes the pons, medulla oblongata, and cerebellum.

hinge joint

Synovial joint at which the convex surface of one bone articulates with the concave surface of a second bone; includes the elbow, knee, ankle, and interphalangeal joints; functionally classified as a uniaxial joint.

histamine

Vasoactive (active on blood vessels) mediator in granules of mast cells and is the primary cause of allergies and anaphylactic shock.

histology

Microscopic study of tissue architecture, organization, and function.

homeostasis

Steady state of body systems that living organisms maintain.

homogeneous

Condition in which solute molecules are distributed equally in a solution.

hormone

Secretion of an endocrine organ that travels via the bloodstream or lymphatics to induce a response in target cells or tissues in another part of the body.

host

(In immunology) referring to the organism in, or on, which a pathogen lives.

humerus

Single bone of the upper arm.

hyaline cartilage

Most common type of cartilage, smooth and made of short collagen fibers embedded in a chondroitin sulfate ground substance.

hydrocarbon

Organic compound, or portion of a molecule, composed entirely of hydrogen and carbon atoms.

hydrogen bond

Dipole-dipole bond in which a hydrogen atom covalently bonded to an electronegative atom is weakly attracted to a second electronegative atom.

hydrolysis

Chemical reaction in which a molecule water is split into H and OPH, thereby breaking a bond and severing a compound.

hydrophilic

“Water loving”; a molecule or portion thereof that is polar and therefore water soluble.

hydrophobic

“Water hating”; a molecule or portion thereof that is nonpolar and therefore water insoluble.

hydroxyapatite

A form of calcium phosphate mineral found in bones (also hydroxylapatite).

hydroxyl

A functional group, OH, present in many organic compounds including alcohols.

hyoid bone

Small, U-shaped bone located in upper neck that does not contact any other bone.

hyperextension

Excessive extension of joint, beyond the normal range of movement.

hyperflexion

Excessive flexion of joint, beyond the normal range of movement.

hyperpolarization

Change in cell membrane potential below resting potential (<-70mV).

hypertonic

Describes a solution concentration that is higher than a reference concentration.

hypochondriac region

Abdominopelvic region (left or right) located under the lowest ribs in the superior corners of the abdominopelvic cavity.

hypodermis

Connective tissue connecting the integument to the underlying bone and muscle.

hypogastric region

Central inferior abdominopelvic region.

hypothalamus

Region of the brain inferior to the thalamus that functions in neural and endocrine signaling, temperature regulation, and control of the autonomic nervous system.

hypotonic

Describes a solution concentration that is lower than a reference concentration.

iliac region

Abdominopelvic region in the left or right inferior corners of the abdomen, below the hip bone.

iliacus

Muscle that, along with the psoas major, makes up the iliopsoas.

iliopsoas group

Muscle group consisting of iliacus and psoas major muscles that flexes the thigh at the hip, rotates it laterally, and flexes the trunk of the body onto the hip.

ilium

Superior portion of the hip bone.

incus

Ossicle of the middle ear (popularly called the anvil) that connects the malleus to the stapes.

inferior

Describes a position below or lower than another part of the body proper; near or toward the tail (in humans, the coccyx, or lowest part of the spinal column); also referred to as caudal.

inferior articular process

Bony process that extends downward from the vertebral arch of a vertebra that articulates with the superior articular process of the next lower vertebra.

inferior colliculus

Half of the midbrain tectum that is part of the brain stem auditory pathway.

inferior vena cava

Large systemic vein that returns blood to the heart from the inferior portion of the body.

infraspinatus

Muscle that laterally rotates the arm.

inner ear

Structure within the temporal bone that contains the sensory apparati of hearing and balance.

inner synaptic layer

Layer in the retina where bipolar cells connect to ganglion cells.

innermost intercostal

The deepest intercostal muscles that draw the ribs together.

inorganic compound

A substance that does not contain both carbon and hydrogen.

insertion

End of a skeletal muscle that is attached to the structure (usually a bone) that is moved when the muscle contracts.

insulin

Hormone that enhances the cellular uptake and utilization of glucose, thereby decreasing blood glucose levels.

integral protein

Membrane-associated protein that spans the entire width of the lipid bilayer.

integumentary system

Skin and its accessory structures.

intermediate

Describes a position between a more medial and a more lateral structure.

internal intercostal

Muscles the intermediate intercostal muscles that draw the ribs together.

internal oblique

Flat, intermediate abdominal muscle with fascicles that run perpendicular to those of the external oblique.

interoception

Sensation of stimuli from internal organs.

interoceptor

Sensory receptor that is positioned to interpret stimuli from internal organs, such as stretch receptors in the wall of blood vessels.

interosseous membrane

Wide sheet of fibrous connective tissue that fills the gap between two parallel bones, forming a syndesmosis; found between the radius and ulna of the forearm and between the tibia and fibula of the leg.

interphalangeal joint

Articulation between adjacent phalanx bones of the hand or foot digits.

interstitial fluid (IF)

Extracellular fluid in the small spaces between cells not contained within blood vessels.

intervertebral disc

Structure located between the bodies of adjacent vertebrae that strongly joins the vertebrae; provides padding, weight bearing ability, and enables vertebral column movements.

intracellular fluid (ICF)

Fluid inside cells.

intramembranous ossification

Process by which bone forms directly from mesenchymal tissue.

inversion

Foot movement involving the intertarsal joints of the foot in which the bottom of the foot is turned toward the midline.

involuntary

(In physiology) though under nervous control (usually from the brain), control is not conscious.

ion

Atom with an overall positive or negative charge. Many function as electrolytes.

ionic bond

Attraction between an anion and a cation.

iris

Colored portion of the anterior eye that surrounds the pupil.

ischial tuberosity

Large, roughened protuberance that forms the posteroinferior portion of the hip bone; weight-bearing region of the pelvis when sitting.

ischium

Superior portion of the hip bone.

isotonic

Describes a solution concentration that is the same as a reference concentration.

joint

Site at which two or more bones or bone and cartilage come together (articulate).

joint cavity

Space enclosed by the articular capsule of a synovial joint that is filled with synovial fluid and contains the articulating surfaces of the adjacent bones.

jugular vein

One of a pair of major veins located in the neck region that flows parallel to the common carotid artery that is more or less its counterpart; primarily drains blood from the brain, receives the superficial facial vein, and empties into the subclavian vein.

keratin

Type of structural protein that gives skin, hair, and nails its hard, water-resistant properties.

keratinocyte

Cell that produces keratin and is the most predominant type of cell found in the epidermis.

keratohyalin

Granulated protein found in the stratum granulosum.

kinesthesia

Sense of body movement based on sensations in skeletal muscles, tendons, joints, and the skin.

kinetic energy

Energy that matter possesses because of its motion.

lacrimal duct

Duct in the medial corner of the orbit that drains tears into the nasal cavity.

lacrimal gland

Gland lateral to the orbit that produces tears to wash across the surface of the eye.

lactic acid

A metabolic byproduct of cellular respiration in the absence of oxygen. It is ultimately converted back into glucose by the liver.

lacuna

(Plural = lacunae) small spaces in bone or cartilage tissue that cells occupy.

lamellae

Concentric rings of calcified matrix that form an osteon.

lamellated corpuscle

Encapsulated mechanoreceptor cell found in the skin that responds to pressure and touch.

Langerhans cell

Specialized dendritic cell found in the stratum spinosum that functions as a macrophage.

larynx

cartilaginous structure that produces the voice, prevents food and beverages from entering the trachea, and regulates the volume of air that enters and leaves the lungs.

latch-bridges

Interactions between actin and myosin filaments in smooth muscle that differ from a cross-bridge in striated muscles that have sarcomeres. The latch state is a prolonged interaction that slowly dissociates and is not ATP-dependent.

lateral

Describes the side or direction toward the side of the body.

lateral geniculate nucleus

Thalamic target of the ganglion cells that projects to the visual cortex.

lateral horn

Region of the spinal cord gray matter in the thoracic, upper lumbar, and sacral regions that is the central component of the sympathetic division of the autonomic nervous system.

lateral ventricles

Portions of the ventricular system that are in the region of the cerebrum.

latissimus dorsi

Broad, triangular axial muscle located on the inferior part of the back.

leakage channel

Ion channel (facilitated diffusion) that opens randomly and is not gated to a specific event, also known as a non-gated channel.

left lumbar region

the lumbar spine consists of the five vertebrae in your lower back.

lens

Component of the eye that focuses light on the retina.

leukocyte

White blood cell.

lever

Simple machine consisting of a beam or rigid rod (bone) pivoted at a fixed hinge, or fulcrum (joint).

ligament

Strong connective tissue bands that hold the bones at a moveable joint together.

ligand-gated channel

A channel protein (facilitated diffusion) that is activated (opens) when a molecule (such as a neurotransmitter) binds to it.

limbic system

Structures at the edge (limit) of the boundary between the forebrain and hindbrain that are most associated with emotional behavior and memory formation.

linea alba

Long, linear muscle that extends along the middle of the trunk.

lipid

Class of nonpolar organic compounds built from hydrocarbons and distinguished by the fact that they are not soluble in water.

load

See resistance

longitudinal plane

See parasagittal plane

longus

Long

lumbar

Lower back, below the ribs.

lumbar region

Left or right central abdominopelvic region.

lumbar vertebrae

Five vertebrae numbered as L1–L5 that are located in lumbar region (lower back) of the vertebral column.

lymph

Fluid contained within the lymphatic system, consisting of interstitial fluid, leukocytes (white blood cells), proteins (including antibodies), and fats.

lymphocyte

White blood cell characterized by a large nucleus and small rim of cytoplasm.

lysosome

Membrane-bound cellular organelle originating from the Golgi apparatus and containing digestive enzymes.

macromolecule

Large molecule formed by covalent bonding; classes of macromolecule discussed in this course include carbohydrates, lipids, proteins, and nucleic acids.

macrophage

Ameboid (irregular outline with peripheral projections) phagocyte found in several tissues throughout the body.

macula

Enlargement at the base of a semicircular canal at which transduction of equilibrium stimuli takes place within the ampulla.

macula lutea

A pigmented area in the middle of the retina, contains the fovea.

malleus

Ossicle of the middle ear (popularly called the hammer) that is directly attached to the tympanic membrane.

mammary gland

Milk-producing gland in mammals.

mandible

Unpaired bone that forms the lower jaw bone; the only moveable bone of the skull.

manubrium

Expanded, superior portion of the sternum.

mass number

Sum of the number of protons and neutrons in the nucleus of an atom.

mast cell

Cell found in the skin and the lining of body cells that contains cytoplasmic granules with vasoactive mediators such as histamine.

mastoid antrum

An air space in the tympanic bone, posterior to (and connected with) the middle ear.

mastoid process

Large bony prominence on the inferior, lateral skull, just behind the earlobe.

matrix

(In connective tissue) extracellular material that is produced by the cells embedded in it, containing ground substance and fibers.

matter

Scientifically, a physical substance; that which occupies space and has mass

maxilla

See maxillary bone

maxillary bone

(Also, maxilla) paired bones that form the upper jaw and anterior portion of the hard palate.

maximus

Largest

mechanically gated channel

Ion channel protein (facilitated diffusion) that opens when a physical event directly affects the structure of the protein.

mechanoreceptor

Receptor cell that transduces mechanical stimuli into an electrochemical signal.

medial

Describes the middle or direction toward the middle of the body.

mediastinum

A central compartment in the thoracic cavity located intermediate to the left and right pleural cavities.

medulla

Lowest (most inferior) part of the brain, controlling many autonomic functions including heart rate, breathing, and digestion.

medulla oblongata

Lowest (most inferior) part of the brain, controlling many autonomic functions including heart rate, breathing, and digestion.

medullary cavity

Hollow region of the diaphysis; filled with yellow marrow.

Meissner corpuscle

(Also, tactile corpuscle) receptor in the skin that responds to light touch.

melanin

Pigment that determines the color of hair and skin.

melanocyte

Cell found in the stratum basale of the epidermis that produces the pigment melanin.

membrane potential

Distribution of charge across the cell membrane, based on the charges of ions.

meninges

Protective outer coverings of the CNS composed of connective tissue.

meniscus

See articular disc

Merkel cell

Receptor cell in the stratum basale of the epidermis that responds to the sense of touch.

Merkel cells

Receptor cell in the stratum basale of the epidermis that responds to the sense of touch.

merocrine gland

Gland whose secretions are excreted by exocytosis.

mesenchyme

Embryonic tissue from which connective tissue cells derive.

Messenger RNA (mRNA)

A single-stranded molecule consisting of ribonucleotides that is produced through the process of transcription and is complementary to a specific DNA sequence.

metabolism

Sum of all catabolic and anabolic reactions that take place in the body.

metacarpal

One of the five long bones that form the palm of the hand; numbered 1–5, starting on the lateral (thumb) side of the hand.

metatarsal

One of the five elongated bones that forms the anterior half of the foot; numbered 1–5, starting on the medial side of the foot.

methyl

A chemical function group, CH3, a component of fatty acids.

micturition

Also called urination or voiding.

midbrain

Middle region of the adult brain that develops from the mesencephalon.

middle ear

Space within the temporal bone between the ear canal and bony labyrinth where the ossicles amplify sound waves from the tympanic membrane to the oval window.

midsagittal plane

A sagittal plane on the midline, dividing the body into equal left and right halves (also medial plane).

mitochondrion

One of the cellular organelles bound by a double lipid bilayer that function primarily in the production of cellular energy (ATP).

mitosis

Division of genetic material, during which the cell nucleus breaks down and two new, fully functional, nuclei are formed. Usually immediately followed by cytokinesis (cell division).

molecular chaperones

A family of proteins that function to facilitate conformational change in other proteins.

molecule

Two or more atoms covalently bonded together.

monocytes

Precursor to macrophages and dendritic cells seen in the blood.

monomer

A molecule that can react with other similar monomers to form a polymer (e.g., amino acids combine to form proteins).

monosaccharide

Five or six-carbon molecule that are monomers of carbohydrates; examples include glucose, fructose, galactose, ribose, and deoxyribose.

monounsaturated

Fats having only one carbon double-bond in the fatty acid chains.

multiaxial

Type of diarthrosis; a joint that allows for movements within three planes (three axes).

multiaxial joint

Type of diarthrosis; a joint that allows for movements within three planes (three axes).

multicellular

Consisting of more than one cell (as opposed to organisms such as bacteria, which are unicellular).

multipolar

Shape of a neuron that has multiple processes—the axon and two or more dendrites.

multipotent

Describes the condition of being able to differentiate into different types of cells within a given cell lineage or small number of lineages, such as a red blood cell or white blood cell.

myelin

Lipid-rich insulating substance surrounding the axons of many neurons, allowing for faster transmission of electrical signals.

myelin sheath

Lipid-rich layer of insulation that surrounds an axon, formed by oligodendrocytes in the CNS and Schwann cells in the PNS; facilitates the transmission of electrical signals.

myocyte

Muscle cell (also muscle fiber).

myofibril

Long, cylindrical organelle that runs parallel within the muscle fiber and contains the sarcomeres.

myosin

Protein that makes up most of the thick cylindrical myofilament within a sarcomere muscle fiber.

negative feedback

Homeostatic mechanism that tends to stabilize an upset in the body’s physiological condition by preventing an excessive response to a stimulus, typically as the stimulus is removed.

nerve

Cord-like bundle of axons located in the peripheral nervous system that transmits sensory input and response output to and from the central nervous system.

neural tunic

Layer of the eye that contains nervous tissue, namely the retina.

neuroglia

Supportive neural cells.

neuromuscular junction

Synapse between the axon terminal of a motor neuron and the section of the membrane of a muscle fiber with receptors for the acetylcholine released by the terminal.

neurons

Excitable neural cell that transfer nerve impulses.

neurotransmitter

Chemical signal that is released from the synaptic end bulb of a neuron to cause a change in the target cell.

neutron

A heavy subatomic particle having no electrical charge and found in the atom’s nucleus.

nociception

Sensing pain.

nociceptor

Receptor cell that senses pain stimuli.

node of Ranvier

Gap between two myelinated regions of an axon, allowing for strengthening of the electrical signal as it propagates down the axon.

nonpolar

Opposite of polar; molecule with electrons that are relatively equally shared in covalent bonds.

norepinephrine

Signaling molecule released as a neurotransmitter by most postganglionic sympathetic fibers as part of the sympathetic response or as a hormone into the bloodstream from the adrenal medulla.

nuclear envelope

Membrane that surrounds the nucleus; consisting of a double lipid-bilayer.

nuclear pore

One of the small, protein-lined openings found scattered throughout the nuclear envelope.

nuclei

(In nervous system) a localized collection of neuron cell bodies that are functionally related; a “center” of neural function (plural= nuclei).

nucleolus

Small region of the nucleus that functions in ribosome synthesis.

nucleotide

Class of organic compounds composed of one or more phosphate groups, a pentose sugar, and a base.

nucleus
nucleus (cell)

Cell’s central organelle; contains the cell’s DNA.

nucleus (nervous tissue)

(In nervous system) a localized collection of neuron cell bodies that are functionally related; a “center” of neural function (plural= nuclei).

nutrient foramen

Small opening in the middle of the external surface of the diaphysis, through which an artery enters the bone to provide nourishment.

oblique

At an angle.

occipital

Unpaired bone that forms the posterior portions of the braincase and base of the skull.

oculomotor nerve

Third cranial nerve; responsible for contraction of four of the extraocular muscles, the muscle in the upper eyelid, and pupillary constriction.

olfaction

Referring to the sense of smell.

olfactory bulb

Central target of the first cranial nerve; located on the ventral surface of the frontal lobe in the cerebrum.

olfactory epithelium

Region of the nasal epithelium where olfactory neurons are located.

olfactory sensory neuron

Receptor cell of the olfactory system, sensitive to the chemical stimuli of smell, the axons of which compose the first cranial nerve.

oligodendrocyte

Glial cell type in the CNS that provides the myelin insulation for axons in tracts.

oligodendrocytes

Glial cell type in the CNS that provides the myelin insulation for axons in tracts.

opsin

Protein that contains the photosensitive cofactor retinal for phototransduction.

optic chiasm

Intersect point in the visual system at which medial retina fibers cross to the other side of the brain.

optic disc

Spot on the retina at which ganglion cell axons leave the eye and blood vessels of the inner retina pass.

optic nerve

Second cranial nerve, which is responsible for visual sensation.

optic tract

Name for the fiber structure containing axons from the retina posterior to the optic chiasm representing their CNS location.

orbit

(In anatomy), the openings for eyes in the skull.

organ

An anatomically distinct structure of the body composed of two or more tissue types.

organ of Corti

Structure in the cochlea in which hair cells transduce movements from sound waves into electrochemical signals.

organ system

Group of organs that work together to carry out a particular function.

organelle

Any of several different types of membrane-enclosed specialized structures in the cell that perform specific functions for the cell.

organic compound

A substance that contains both carbon and hydrogen.

organism

Living being that has a cellular structure and that can independently perform all physiologic functions necessary for life.

orifices

Opening such as mouth, nares, anus, etc.

origin

End of a skeletal muscle that is attached to another structure (usually a bone) in a fixed position.

oris

Mouth

osmoreceptor

Receptor cell that senses differences in the concentrations of bodily fluids on the basis of osmotic pressure.

osmosis

Diffusion of water molecules down their concentration gradient across a selectively permeable membrane.

ossicles

Three small bones in the middle ear.

ossification

(Also, osteogenesis) bone formation.

ossification centre

Cluster of osteoblasts found in the early stages of intramembranous ossification.

osteoblast

Cell responsible for forming new bone.

osteoclast

Cell responsible for resorbing bone.

osteocyte

Primary cell in mature bone; responsible for maintaining the matrix.

osteogenesis

See ossification

osteogenic cell

Undifferentiated cell with high mitotic activity; the only bone cells that divide; they differentiate and develop into osteoblasts.

osteoid

Uncalcified bone matrix secreted by osteoblasts.

osteon

(Also, Haversian system) basic structural unit of compact bone; made of concentric layers of calcified matrix.

otolithic membrane

Gelatinous substance in the utricle and saccule of the inner ear that contains calcium carbonate crystals and into which the stereocilia of hair cells are embedded.

otoliths

Layer of calcium carbonate crystals located on top of the otolithic membrane.

outer synaptic layer

Layer in the retina at which photoreceptors connect to bipolar cells.

oval window

Membrane at the base of the cochlea where the stapes attaches, marking the beginning of the scala vestibuli.

oviduct

See uterine tube

oxytocin

Hormone stored in the posterior pituitary gland and important in stimulating uterine contractions in labor, milk ejection during breastfeeding, and feelings of attachment (also produced in males).

palpebral conjunctiva

Membrane attached to the inner surface of the eyelids that covers the anterior surface of the cornea.

papilla

For gustation, a bump-like projection on the surface of the tongue that contains taste buds.

parasagittal plane

A sagittal plane that does not divide the body into equal left and right halves (also longitudinal section).

parasympathetic division

Division of the autonomic nervous system responsible for restful and digestive functions.

parenchyma

Functional cells of a gland or organ, in contrast with the supportive or connective tissue of a gland or organ.

parietal

Facing the body wall.

parietal bone

Paired bones that form the upper, lateral sides of the skull.

passive transport

Form of transport across the cell membrane that does not require input of cellular energy.

patella

Knee cap.

patellar ligament

Extension of the quadriceps tendon below the patella.

patellar tendon

See quadriceps tendon

pathogen

An infectious agent that causes disease, typically a bacterium, virus, fungus, or microscopic parasite.

pectoral girdle

Shoulder girdle; the set of bones, consisting of the scapula and clavicle, which attaches each upper limb to the axial skeleton.

pectoralis major

Thick, fan-shaped axial muscle that covers much of the superior thorax.

pelvic girdle

Hip girdle; consists of a single hip bone, which attaches a lower limb to the sacrum of the axial skeleton.

pelvis

The lower part of the trunk, between the abdomen and the thighs together with its embedded skeleton

peptide

As a molecule, a short chain of amino acids. Also refers to something related to proteins.

peptide bond

A type of covalent bond occurring between amino acids.

perforating canal

(Also, Volkmann’s canal) channel that branches off from the central canal and houses vessels and nerves that extend to the periosteum and endosteum.

pericardial fluid

Fluid found in the pericardium.

pericardium

Cavity surrounding the heart filled with a lubricating serous fluid that reduces friction as the heart contracts (also, pericardial cavity or cardiac sac).

perichondrium

Layer of dense irregular connective tissue surrounding cartilage.

perilymph

Extracellular fluid of the inner ear, lying between the membranous labyrinth and the bony labyrinth.

perimysium

Connective tissue that bundles skeletal muscle fibers into fascicles within a skeletal muscle.

periodic table of the elements

An arrangement of the elements in a table according to their atomic number; elements having similar properties because of their electron arrangements compose columns in the table, while elements having the same number of valence shells compose rows in the table. See Appendix I.

periosteum

Fibrous membrane covering the outer surface of bone and continuous with ligaments.

peripheral

Describes a position toward the outer edge (periphery) of a structure or organ system.

peripheral protein

Membrane-associated protein that does not span the width of the lipid bilayer, but is attached peripherally to integral proteins, membrane lipids, or other components of the membrane.

peristalsis

A rhythmic contraction of smooth muscle layers that line tubes, such as the esophagus, and propel substances forward.

peritoneum

Serous membrane that lines the abdominopelvic cavity and covers the organs found there.

phagocytosis

Cell process (a form of endocytosis) in which a cell engulfs and ingests another large particle or cell.

phalanx

(Plural = phalanges) one of the bones that forms the fingers or toes.

pharynx

Throat

pheromone

A chemical, either secreted or excreted, that produces a social response in other individuals.

phosphate

Chemical functional group, PO4-, a component of phospholipids and nucleic acids (including ATP).

phospholipid

An amphipathic lipid molecule containing a phosphate head (polar) and two fatty acid tails (non-polar). The major molecule comprising plasma membranes.

phospholipids

An amphipathic lipid molecule containing a phosphate head (polar) and two fatty acid tails (non-polar). The major molecule comprising plasma membranes.

phosphorylation

Addition of one or more phosphate groups to an organic compound.

photoisomerization

Chemical change in the retinal molecule that alters the bonding so that it switches from the 11-cis-retinal isomer to the all-trans-retinal isomer.

photon

Individual “packet” of light.

photoreceptor

Receptor cell specialized to respond to light stimuli.

pia mater

Thin, innermost membrane of the meninges that directly covers the surface of the CNS.

pinocytosis

Endocytosis of fluid.

pituitary gland

Bean-sized organ suspended from the hypothalamus that produces, stores, and secretes hormones in response to hypothalamic stimulation (also called hypophysis).

pivot joint

Synovial joint at which the rounded portion of a bone rotates within a ring formed by a ligament and an articulating bone; functionally classified as uniaxial joint.

plane

(In anatomy) imaginary two-dimensional surface that passes through the body.

plane joint

Synovial joint formed between the flattened articulating surfaces of adjacent bones; functionally classified as a multiaxial joint.

plantar flexion

Foot movement at the ankle in which the heel is lifted off of the ground.

plasma

An extracellular fluid, the fluid component of blood.

plasma cell

Differentiated B cell that is actively secreting antibody.

platelets

(Also, thrombocytes) one of the formed elements of blood that consists of cell fragments broken off from megakaryocytes.

pleura

Serous membrane that lines the pleural cavity and covers the lungs.

pleural cavity

The space between the visceral and parietal pleurae.

pleural fluid

Substance that acts as a lubricant for the visceral and parietal layers of the pleura during the movement of breathing.

polar

Molecule with regions that have opposite charges resulting from uneven numbers of electrons in the nuclei of the atoms participating in the covalent bond.

polarity

Information flow in one direction.

polarity (neurons)

Information flow in one direction.

pollex

Thumb

polymer

A molecule formed of many monomers together forming a macromolecule.

polypeptide

A chain of amino acids, typically fewer than 100.

polysaccharide

A complex molecule formed of many (up to a thousand or more) monosaccharides (e.g., glycogen, starches, and cellulose).

polyunsaturated 

Fats that contain more than one carbon double-bond within their fatty acid chains.

pons

Portion of the brainstem connecting the medulla oblongata with the midbrain. Serves as a connection to cerebellum, as well as functions including sleep cycles and the origin of some cranial nerves.

popliteus

Back of the knee.

positive feedback

Mechanism that intensifies a change in the body’s physiological condition in response to a stimulus.

posterior

Describes the back or direction toward the back of the body; also referred to as dorsal.

posterior cavity

See dorsal cavity

posterior horn

Gray matter region of the spinal cord in which sensory input arrives, sometimes referred to as the dorsal horn.

postganglionic fibre

Axon from a ganglionic neuron in the autonomic nervous system that projects to and synapses with the target effector; sometimes referred to as a postganglionic neuron.

potential energy

Stored energy matter possesses because of the positioning or structure of its components.

power lever

A lever system that can move a load/resistance with less effort (compared to moving the resistance without a lever system); by definition, the mechanical advantage is greater than one (effort arm > resistance arm).

preganglionic fibre

Axon from a central neuron in the autonomic nervous system that projects to and synapses with a ganglionic neuron; sometimes referred to as a preganglionic neuron.

primary active transport

Active transport using carrier proteins that use ATP (powered by the energy obtained through phosphorylation by ATP).

primary ossification centre

Region, deep in the periosteal collar, where bone development starts during endochondral ossification.

primary structure

The unique amino acid sequence of a protein.

prime mover

See agonist

process

In cells, an extension of a cell body; in the case of neurons, this includes the axon and dendrites.

proliferative zone

Region of the epiphyseal plate that makes new chondrocytes to replace those that die at the diaphyseal end of the plate and contributes to longitudinal growth of the epiphyseal plate.

pronated position

Forearm position in which the palm faces backward.

pronation

Forearm motion that moves the palm of the hand from the palm forward to the palm backward position.

prone

Face down position.

proprioception

Sense of position and movement of the body.

proprioceptor

Receptor cell that senses changes in the position and kinesthetic aspects of the body.

proprioceptors.

Receptor cell that senses changes in the position and kinesthetic aspects of the body.

protein

Class of organic compounds that are composed of many amino acids linked together by peptide bonds.

proteoglycans

A molecule similar in structure to a glycoprotein, consisting of a protein with at least one sugar attached. Proteoglycans are different in that the sugar molecule was produced first.

proton

A heavy subatomic particle having a positive charge and found in the atom’s nucleus.

protraction

Anterior motion of the scapula or mandible.

proximal

Describes a position in a limb that is nearer to the point of attachment or the trunk of the body.

pseudostratified columnar epithelium

Tissue that consists of a single layer of irregularly shaped and sized cells that give the appearance of multiple layers; found in ducts of certain glands and the upper respiratory tract.

psoas major

Muscle that, along with the iliacus, makes up the iliopsoas.

pubic symphysis

Joint formed by the articulation between the pubic bodies of the right and left hip bones.

pubis

Anterior portion of the hip bone.

pupil

Open hole at the center of the iris that light passes through into the eye.

quadriceps

Four muscles that extend and stabilize the knee.

quadriceps femoris

Muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip.

quadriceps tendon

(Also, patellar tendon) tendon common to all four quadriceps muscles, inserts into the patella.

quaternary structure

Protein structure produced by the interaction of two or more identical or different polypeptide chains.

radiocarpal joint

Wrist joint, located between the forearm and hand regions of the upper limb; articulation formed proximally by the distal end of the radius and the fibrocartilaginous pad that unites the distal radius and ulna bone and distally by the scaphoid, lunate, and triquetrum carpal bones.

radius

Bone located on the lateral side of the forearm.

receptor

Protein molecule that contains a binding site for another specific molecule (called a ligand).

receptor cell

Cell that transduces environmental stimuli into neural signals.

receptor-mediated endocytosis

Endocytosis of ligands attached to membrane-bound receptors.

rectus

Straight

rectus abdominis

Long, linear muscle that extends along the middle of the trunk.

rectus femoris

Quadricep muscle on the anterior aspect of the thigh.

red marrow

Connective tissue in the interior cavity of a bone where hematopoiesis takes place.

reflex arc

Circuit of a reflex that involves a sensory input and motor output, or an afferent branch and an efferent branch, and an integrating center to connect the two branches.

refraction

The bending of light as it passes between mediums of different densities.

refractory period

Time after the initiation of an action potential when another action potential cannot be generated.

repolarization

Return of the membrane potential to its normally negative voltage at the end of the action potential.

reserve zone

Region of the epiphyseal plate that anchors the plate to the osseous tissue of the epiphysis.

resistance

(Also, load) the force opposing the action of a lever; in body systems, the resistance may be the mass of the limb (force of gravity acting on the bone) or a load being lifted or moved.

resistance arm

Distance measured from the fulcrum to the resistance (center of gravity or load being moved).

resting membrane potential

The difference in voltage measured across a cell membrane under steady-state conditions, typically -70 mV.

reticular

Fine fibrous protein, made of collagen subunits, which cross-link to form supporting “nets” within connective tissue.

reticular formation

Diffuse region of gray matter throughout the brain stem that regulates sleep, wakefulness, and states of consciousness.

reticular lamina

Matrix containing collagen and elastin secreted by connective tissue; a component of the basement membrane.

retina

Nervous tissue of the eye at which phototransduction takes place.

retinal

Cofactor in an opsin molecule that undergoes a biochemical change when struck by a photon (pronounced with a stress on the last syllable).

retraction

Posterior motion of the scapula or mandible.

rhodopsin

Photopigment molecule found in the rod photoreceptors.

ribonucleic acid (RNA)

Ribose-containing nucleic acid that helps manifest the genetic code as protein.

ribosome

Cellular organelle that functions in protein synthesis.

rigor mortis

Stiffening of the muscles and joints shortly after death due to a lack of ATP availability for breaking cross-bridges.

rod

One of the two types of receptor cells in the retina that is specialized for low-light vision

rotation

Movement of a bone around a central axis (atlantoaxial joint) or around its long axis (proximal radioulnar joint; shoulder or hip joint); twisting of the vertebral column resulting from the summation of small motions between adjacent vertebrae.

round window

Membrane that marks the end of the scala tympani.

Ruffini corpuscle

See bulbous corpuscle

saccule

Structure of the inner ear responsible for transducing linear acceleration in the vertical plane.

sacral

Region of the sacrum, bone forming the back part of the pelvic cavity.

sacrococcygeal curve

Anteriorly concave curvature formed by the sacrum and coccyx; a primary curve of the vertebral column.

sacroiliac joint

Joint formed by the articulation between the auricular surfaces of the sacrum and ilium.

sacrum

Single bone located near the inferior end of the adult vertebral column that is formed by the fusion of five sacral vertebrae; forms the posterior portion of the pelvis.

saddle joint

Synovial joint in which the articulating ends of both bones are convex and concave in shape, such as at the first carpometacarpal joint at the base of the thumb; functionally classified as a biaxial joint.

sagittal plane

Two-dimensional, vertical plane that divides the body or organ into right and left sides.

salivary amylase

Oral enzyme that functions to break down complex carbohydrates into disaccharides.

saltatory conduction

Quick propagation of the action potential along a myelinated axon owing to voltage-gated Na+ channels being present only at the nodes of Ranvier.

sarcolemma

Plasma membrane of a skeletal muscle fiber.

sarcomere

Longitudinally, repeating functional unit of skeletal muscle, with all of the contractile and associated proteins involved in contraction.

sarcoplasm

Cytoplasm of a muscle cell.

sarcoplasmic reticulum (SR)

Specialized smooth endoplasmic reticulum, which stores, releases, and retrieves Ca++.

sartorius

Band-like muscle that flexes, abducts, and laterally rotates the leg at the hip.

saturated fatty acids

A type of fat in which the fatty acid chains contain only single bonds.

scala media

See cochlear duct

scala tympani

Portion of the cochlea that extends from the apex to the round window.

scala vestibuli

Portion of the cochlea that extends from the oval window to the apex.

scapula

Shoulder blade bone located on the posterior side of the shoulder.

Schwann cell

Glial cell type in the PNS that provides the myelin insulation for axons in nerves.

Schwann cells

Glial cell type in the PNS that provides the myelin insulation for axons in nerves.

sclera

White of the eye.

sebaceous gland

Type of oil gland found in the dermis all over the body and helps to lubricate and waterproof the skin and hair by secreting sebum.

second-class lever

A lever system in which the resistance is between the effort and the fulcrum; as the effort arm is always longer than the resistance arm, these are always power levers.

secondary active transport

Active transport using pumps (carrier proteins) that are powered by the potential energy of a concentration gradient (usually of H+ or Na+).

secondary ossification centre

Region of bone development in the epiphyses.

secondary structure

Structure produced from hydrogen bonding between atoms of the polypeptide backbone.

selective permeability

Feature of any barrier that allows certain substances to cross but excludes others.

semicircular canals

Structures within the inner ear responsible for transducing rotational movement information.

semicircular ducts

Part of the membranous labyrinth contained in the semicircular canals.

semimembranosus

The medial of the three muscles that comprise the hamstrings group.

semitendinosus

The medial of the three muscles comprising the hamstring group.

sensory modality

A particular system for interpreting and perceiving environmental stimuli by the nervous system.

serosa

See serous membrane

serous membrane

Membrane that covers organs and reduces friction; also referred to as serosa.

sesamoid

A bone embedded in tendon; the only major sesamoid bone is the patella.

set point

(In physiology) ideal value for a physiological parameter; the level or small range within which a physiological parameter such as blood pressure is stable and optimally healthful, that is, within its parameters of homeostasis.

simple columnar epithelium

Tissue that consists of a single layer of column-like cells; promotes secretion and absorption in tissues and organs.

simple cuboidal epithelium

Tissue that consists of a single layer of cube-shaped cells; promotes secretion and absorption in ducts and tubules.

Simple Diffusion

A form of passive transport across a cell membrane that does not require a membrane protein.

simple squamous epithelium

Tissue that consists of a single layer of flat scale-like cells; promotes diffusion and filtration across surface.

skeletal muscle

Usually attached to bone, under voluntary control, each cell is a fiber that is multinucleated and striated.

smooth muscle

Under involuntary control, moves internal organs, cells contain a single nucleus, are spindle-shaped, and do not appear striated; each cell is a fiber.

Sodium-Potassium Pump

Primary active transport protein that uses ATP hydrolysis to pump 3 sodium ions out of the cell and 2 potassium ions into the cell.

soleus

Wide, flat muscle deep to the gastrocnemius.

solute

Component of a solution, the substance dissolved in a solvent.

solution

In chemistry, a homogeneous liquid mixture in which a solute is dissolved into molecules within a solvent.

solvent

Component of a solution, the substance that dissolves the solute.

soma

In neurons, that portion of the cell that contains the nucleus; the cell body, as opposed to the cell processes (axons and dendrites).

somatic cell

A body cell, excluding germ cells. Normally diploid, each cell containing a complete set of genes.

somatic nervous system

Functional division of the nervous system that is concerned with conscious perception, voluntary movement, and skeletal muscle reflexes.

somatosensation

Sense of touch.

somatotropin

See growth hormone (GH)

special sense

Any sensory system associated with a specific organ structure, namely smell, taste, sight, hearing, and balance.

spectrin

A structural protein that helps maintain cell membrane integrity.

speed lever

A lever system that can move a load/resistance with more effort and greater speed (compared to moving the resistance without a lever system); by definition, the mechanical advantage is less than one (effort arm < resistance arm).

sphenoid bone

Unpaired bone that forms the central base of skull.

sphincter

A ring-shaped smooth muscle that can open or close a passage in the body.

spinal cavity

Division of the dorsal cavity that houses the spinal cord; also referred to as vertebral cavity.

spinous process

Unpaired bony process that extends posteriorly from the vertebral arch of a vertebra.

spiral ganglion

Location of neuronal cell bodies that transmit auditory information along the eighth cranial nerve.

splanchnic nerves

Paired nerves that carry both autonomic and sensory fibers to the internal organs.

spongy bone

(Also, cancellous bone) trabeculated osseous tissue that supports shifts in weight distribution.

stapes

Ossicle of the middle ear (popularly called the stirrup) that is attached to the inner ear.

static equilibrium

Modality of balance relating to position of the head with respect to gravity (“which way is up”) and linear acceleration.

stem cell

Cell that is oligo-, multi-, or pleuripotent that has the ability to produce additional stem cells rather than becoming further specialized.

stereocilia

Array of apical membrane extensions in a hair cell that transduce movements when they are bent.

sternocleidomastoid

Major muscle that laterally flexes and rotates the head.

sternum

Flattened bone located at the center of the anterior chest.

steroid

(Also, sterol) lipid compound composed of four hydrocarbon rings bonded to a variety of other atoms and molecules; not to be confused with anabolic steroids, a synthetic supplement

sterol

See steroid

stratified columnar epithelium

Tissue that consists of two or more layers of column-like cells, contains glands, and is found in some ducts.

stratified cuboidal epithelium

Tissue that consists of two or more layers of cube-shaped cells, found in some ducts.

stratified squamous epithelium

Tissue that consists of multiple layers of cells with the most apical being flat scale-like cells; protects surfaces from abrasion.

stratum basale

Deepest layer of the epidermis, made of epidermal stem cells.

stratum corneum

Most superficial layer of the epidermis.

stratum granulosum

Layer of the epidermis superficial to the stratum spinosum.

stratum lucidum

Layer of the epidermis between the stratum granulosum and stratum corneum, found only in thick skin covering the palms, soles of the feet, and digits.

stratum spinosum

Layer of the epidermis superficial to the stratum basale, characterized by the presence of desmosomes.

stressor

(In physiology) any stimulus that causes an imbalance in the internal environment.

striation

Alignment of parallel actin and myosin filaments, which form a banded pattern.

subarachnoid space

Space between the arachnoid mater and pia mater that contains CSF and the fibrous connections of the arachnoid trabeculae.

subscapularis

Muscle that originates on the anterior scapula and medially rotates the arm.

subthalamus

Nucleus within the basal nuclei that is part of the indirect pathway.

sudoriferous gland

Sweat gland.

sulcus

Groove formed by convolutions in the surface of the cerebral cortex.

superficial

Describes a position closer to the surface of the body.

superior

Describes a position above or higher than another part of the body proper; also referred to as cranial.

superior articular process

Bony process that extends upward from the vertebral arch of a vertebra that articulates with the inferior articular process of the next higher vertebra.

superior colliculus

Half of the midbrain tectum that is responsible for aligning visual, auditory, and somatosensory spatial perceptions.

supinated position
supination

Forearm motion that moves the palm of the hand from the palm backward to the palm forward position.

supine

Face up.

supraspinatus

Muscle that abducts the arm.

suspensory ligament

(Also zonule fibre) fibrous connections between the ciliary body and the lens.

suture

Fibrous joint that connects the bones of the skull (except the mandible); an immobile joint (synarthrosis).

sympathetic chain ganglia

Series of ganglia adjacent to the vertebral column that receive input from central sympathetic neurons.

sympathetic division

Branch of the autonomic nervous system associated with emergency systems (“fight or flight”).

symphysis

Type of cartilaginous joint where the bones are joined by fibrocartilage.

synapse

Narrow junction across which a chemical signal passes from neuron to the next, initiating a new electrical signal in the target cell.

synapses

Narrow junction across which a chemical signal passes from neuron to the next, initiating a new electrical signal in the target cell.

synaptic cleft

Small gap between cells in a chemical synapse where neurotransmitter diffuses from the presynaptic element to the postsynaptic element.

synaptic end bulb

Swelling at the end of an axon where neurotransmitter molecules are released onto a target cell across a synapse.

synarthrosis

Immobile or nearly immobile joint.

synchondrosis

Type of cartilaginous joint where the bones are joined by hyaline cartilage.

syncytium

A multinucleate cell formed by the fusion of multiple cells or the division of nuclei.

syndesmosis

Type of fibrous joint in which two separated, parallel bones are connected by an interosseous membrane.

synergist

Muscle whose contraction helps a prime mover in an action.

synovial fluid

Thick, lubricating fluid that fills the interior of a synovial joint.

synovial joint

Joint at which the articulating surfaces of the bones are located within a joint cavity formed by an articular capsule.

synovial membrane

Thin layer that lines the inner surface of the joint cavity at a synovial joint; produces the synovial fluid.

tactile corpuscle

(Also, Meissner corpuscle) receptor in the skin that responds to light touch.

talus

Tarsal bone that articulates superiorly with the tibia and fibula at the ankle joint; also articulates inferiorly with the calcaneus bone and anteriorly with the navicular bone.

tarsal

One of the seven bones that make up the posterior foot; includes the calcaneus, talus, navicular, cuboid, medial cuneiform, intermediate cuneiform, and lateral cuneiform bones.

taste bud

Structures within a papilla on the tongue that contain gustatory receptor cells.

tectorial membrane

Component of the organ of Corti that lays over the hair cells, into which the stereocilia are embedded.

temporal bone

Paired bones that form the lateral, inferior portions of the skull, with squamous, mastoid, and petrous portions.

tendon

Dense regular connective tissue that attaches skeletal muscle to bone.

teres major

Muscle that extends the arm and assists in adduction and medial rotation of it.

teres minor

Muscle that laterally rotates and extends the arm.

tertiary structure

the overall three-dimensional arrangement of a polypeptide in space.

thalamus

Major region of the diencephalon that is responsible for relaying information between the cerebrum and the hindbrain, spinal cord, and periphery.

thermoreceptor

Sensory receptor specialized for temperature stimuli.

third ventricle

Portion of the ventricular system that is in the region of the diencephalon.

third-class lever

A lever system in which the effort is between the resistance and the fulcrum; the most common lever type in the bottom, these are always speed levers as the effort arm is always shorter than the resistance arm.

thoracic

Mid-back, where ribs attach to vertebrae.

thoracic cage

Consists of 12 pairs of ribs and sternum.

thoracic cavity

Division of the anterior (ventral) cavity that houses the heart, lungs, esophagus, and trachea.

thoracic curve

Anteriorly concave curvature of the thoracic vertebral column region; a primary curve of the vertebral column.

thoracic duct

Major lymph vessel draining lymph into the circulatory system (blood) at the left subclavian vein.

thoracic vertebrae

Twelve vertebrae numbered as T1–T12 that are located in the thoracic region (upper back) of the vertebral column.

thoracolumbar system

Alternate name for the sympathetic division of the autonomic nervous system that is based on the anatomical location of central neurons in the lateral horn of the thoracic and upper lumbar spinal cord.

tibia

Shin bone; the large, weight-bearing bone located on the medial side of the leg.

tibialis anterior

Muscle located on the lateral surface of the tibia.

tissue

Group of many similar cells (though sometimes composed of a few related types) that work together to perform a specific function.

titin

the largest protein in the human body, which is responsible for passive elasticity in muscle cells.

tone

The default tension in a resting muscle that will optimize contraction ability.

trabeculae

(Singular= trabecula) spikes or sections of the lattice-like matrix in spongy bone.

trachea

Tube composed of cartilaginous rings and supporting tissue that connects the lung bronchi and the larynx; provides a route for air to enter and exit the lung.

tract

Cord-like bundle of axons located in the peripheral nervous system that transmits sensory input and response output to and from the central nervous system.

transcription

during gene expression, the initial process that occurs inside the nucleus, in which a strand of messenger RNA is produced using a specific DNA sequence as a template.

transduction

Process of changing an environmental stimulus into the electrochemical signals of the nervous system.

Transmembrane proteins

Membrane proteins that span the entire width of the plasma membrane.

transverse foramen

Paired bony processes that extends laterally from the vertebral arch of a vertebra.

transverse plane

Two-dimensional, horizontal plane that divides the body or organ into superior and inferior portions.

transverse process

Paired bony processes that extends laterally from the vertebral arch of a vertebra.

transversus abdominis

Deep layer of the abdomen that has fascicles arranged transversely around the abdomen.

trapezius

Muscle that stabilizes the upper part of the back.

triceps brachii

Three-headed muscle that extends the forearm.

triglyceride

An ester formed from glycerol and three fatty acid chains.

trochlear nerve

Fourth cranial nerve; responsible for contraction of one of the extraocular muscles.

tropomyosin

Regulatory protein that covers myosin-binding sites to prevent actin from binding to myosin.

troponin

Regulatory protein that binds to actin, tropomyosin, and calcium.

true ribs

Vertebrosternal ribs 1–7 that attach via their costal cartilage directly to the sternum.

tympanic membrane

Ear drum.

ulna

Bone located on the medial side of the forearm.

umbilical region

Central abdominopelvic region including the belly button.

uniaxial joint

Type of diarthrosis; joint that allows for motion within only one plane (one axis).

uterine tube

(Also, fallopian tube or oviduct) duct that facilitates transport of an ovulated oocyte to the uterus.

utricle

Structure of the inner ear responsible for transducing linear acceleration in the horizontal plane.

vagus nerve

Tenth cranial nerve; responsible for the autonomic control of organs in the thoracic and upper abdominal cavities.

valence shell

Outermost electron shell of an atom.

vascular

Relating to circulation of blood.

vascular tunic

Middle layer of the eye primarily composed of connective tissue with a rich blood supply.

vasodilation

Opening up, or increasing interior (lumen) diameter of a blood vessel.

ventral

See anterior

ventral cavity

Larger body cavity located anterior to the posterior (dorsal) body cavity; includes the serous membrane-lined pleural cavities for the lungs, pericardial cavity for the heart, and peritoneal cavity for the abdominal and pelvic organs; also referred to as anterior body cavity.

ventricle

Remnants of the hollow center of the neural tube that are spaces for cerebrospinal fluid to circulate through the brain.

vertebra

Individual bone in the neck and back regions of the vertebral column.

vertebral (spinal) canal

Bony passageway within the vertebral column for the spinal cord that is formed by the series of individual vertebral foramina.

vertebral arch

Bony arch formed by the posterior portion of each vertebra that surrounds and protects the spinal cord.

vertebral cavity

See spinal cavity

vertebral column

Entire sequence of bones that extend from the skull to the tailbone.

vertebral foramen

Opening associated with each vertebra defined by the vertebral arch that provides passage for the spinal cord.

vesicle

Membrane-bound structure that contains materials within or outside of the cell.

vestibular ganglion

Location of neuronal cell bodies that transmit equilibrium information along the eighth cranial nerve.

vestibular membrane

Membrane separating the cochlear duct from the scala vestibuli.

vestibule

In the ear, the portion of the inner ear responsible for the sense of equilibrium.

vestibulocochlear nerve

Eighth cranial nerve; responsible for the sensations of hearing and balance.

visceral

Facing the organs (opposite of parietal).

viscous

Thick consistency between solid and liquid.

visual acuity

Property of vision related to the sharpness of focus, which varies in relation to retinal position.

vitamin

Organic compound required by the body to perform biochemical reactions like metabolism and bone, cell, and tissue growth.

vitreous humour

Viscous fluid that fills the posterior chamber of the eye.

Volkmann's canal

See perforating canal

voltage-gated channel

Ion channel that opens because of a change in the charge distributed across the membrane where it is located.

voluntary

(In physiology) under conscious control of the brain.

white matter

Regions of the nervous system containing mostly myelinated axons, making the tissue appear white because of the high lipid content of myelin.

xiphoid process

Small process that forms the inferior tip of the sternum.

yellow marrow

Connective tissue in the interior cavity of a bone where fat is stored.

Z-disc

(Also Z-line) structure at the end of sarcomeres to which actin is anchored.

Z-line

See Z-disc

zone of calcified matrix

Region of the epiphyseal plate closest to the diaphyseal end; functions to connect the epiphyseal plate to the diaphysis.

zone of maturation and hypertrophy

Region of the epiphyseal plate where chondrocytes from the proliferative zone grow and mature and contribute to the longitudinal growth of the epiphyseal plate.

zonule fibre

See suspensory ligament

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