The urinary system consists of the kidneys, two ureters, the urinary bladder, and the urethra. Blood flows through the kidneys as they filter out waste such as urea. The urine produced by the kidneys goes through the ureters. It then waits in the urinary bladder, until it goes out through the urethra.
- Excretion- remove waste products from the blood
- Regulation of blood volume and pressure- kidneys control amount of extracelluar fluid, can make dilute or very concentrated urine
- Regulation of the concentration of solutes in the blood- kidneys regulate molecules and ions like glucose, sodium, hydrogen carbonate
- Regulation of red blood cell synthesis- kidneys secrete erythropoietin, which regulates blood cell production in bone marrow
- Vitamin D synthesis- kidneys control blood levels of calcium by regulation synthesis of vitamin D.
Substances Removed by Kidneys
Most of the substances removed are metabolic wastes, produced as by products from normal body function. Some of the most toxic include the nitrogenous wastes.
- Urea- produced in liver by protein metabolism
- Uric Acid- produced in liver by metabolism by nucleic acid metabolism
- Creatinine- produced in muscles by protein metabolism
- (Re)Absorption- movement of a solute across a membrane and incorporation into the body
- Secretion- release of a solute across a membrane, out of the body, in this case from the peritubular capillaries into the tubule.
- Excretion- filtration and removal of solutes out of the body
- Solute- a substance that is dissolved in the blood plasma (ions, waste chemicals, toxins, etc.)
- Clearance- the rate at which a solute is filtered from the blood plasma