Functions of the Renal System

Objective 1

19.1.1 Describe the general functions of the urinary system.

19.1.2 List the organs of the urinary system and identify their locations.

 

 

Overview of Urinary Functions
Regulation of electrolytes Controls levels of various anions and cations
Regulation of pH Controls pH by secreting H+ into the urine and return of HCO3– back to the blood
Regulation of blood volume Adjusts blood volume by conserving or eliminating water in the urine
Regulation of blood pressure Adjusts blood pressure by conserving or eliminating Na+ and water in the urine
Maintenance of blood osmolarity Controls blood solute concentration
Production of hormones Releases calcitriol (active vitamin D) to increase calcium levels, releases erythropoietin to increase red blood cell production
Regulation of blood Glucose levels Release glucose, produced by gluconeogenesis, into the blood
Excretion of wastes Excretes ammonia, urea, bilirubin, creatinine, uric acid, and other wastes

 

The renal system is not simply a urinary system (although it’s often called that). It’s not only a waste-removal system; it plays a vital role in maintaining homeostasis. The urinary system assists in controlling the body’s pH, electrolytes, fluid volume, and fluid concentration. The kidneys also produce hormones to regulate red blood cell production and blood calcium levels. A dysfunctional urinary system will have effects on all other systems of the body.

Diagram illustrating the position of the urinary system.

The renal system consists of the kidneys, ureters, bladder, and urethra. The kidneys are positioned in the abdominal cavity between the posterior abdominal wall and the peritoneum. Because only the anterior aspect is covered by the peritoneum, they are said to be retroperitoneal. The kidneys are located in the area of the inferior thoracic vertebrae (T11- T12) and the superior lumbar vertebrae (L1-L2). They are partially protected by the floating ribs (11-12). Because the liver takes up so much space on the right side, the right kidney is slightly lower than the left.

Photograph of a horizontal section of the human abdomen showing the location of the kidneys.
Notice how the kidneys sit behind the abdominal wall and peritoneum (retroperitoneal). The size of the liver causes the right kidney to sit a little lower than the left kidney.

Extending from each kidney is a ureter. The ureter is a tube, which connects the kidney and the bladder and is also retroperitoneal. Both ureters drain into the bladder.

Diagram showing the male urinary system.

The bladder is a hollow, distensible organ in the pelvic cavity, designed to hold urine until it is voided. The bladder can hold an average of 700-800 ml of urine.

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Integrated Human Anatomy and Physiology Copyright © by Travis Price; Jim Hutchins; Justin Burr; Maddison Johnston; Pamela Silberman; Jeffery Speth; Jordan West; Misty Allen; and Elizabeth Rebarchik is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

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