Functions of the Urinary System
The urinary or renal system is a group of organs in the body that filters out excess fluid and other substances from the bloodstream. The purpose of the urinary system is to eliminate wastes from the body, regulate blood volume and pressure, control levels of electrolytes and metabolites, and regulate blood pH. The urinary system organs include the kidneys, ureters, bladder, and urethra. Metabolic wastes and excess ion are filtered out of the blood, combined with water, and leave the body in the form of urine.
There are several functions of the urinary system:
- Removal of metabolic waste products from the body (mainly urea and uric acid)
- Regulation of electrolyte balance (e.g. sodium, potassium and calcium)
- Osmoregulation: control of blood volume and body water content
- Regulation of acid-base homeostasis and blood pH
Components of the Urinary System
Kidneys are the most complex and critical part of the urinary system. The primary function of the kidneys is to maintain a stable internal environment (homeostasis) for optimal cell and tissue metabolism. The kidneys have extensive blood supply via the renal arteries which leave the kidneys via the renal vein.
Nephrons in the kidneys filter blood to remove urea, a waste product formed by the oxidation of proteins, as well as ions like potassium and sodium. The nephrons are made up of a ball of blood capillaries (the glomerulus) and a small rental tube. The resulting urine passes from the renal tube through tubes called ureters and into the bladder. The bladder is flexible and is used as storage until the urine is allowed to pass through the urethra and out of the body. The female and male urinary system are very similar, differing only in the length of the urethra.
Kidneys play a very large role in human osmoregulation by regulating the amount of water reabsorbed from glomerular filtrate in kidney tubules, which is controlled by hormones such as antidiuretic hormone (ADH), aldosterone, and angiotensin II. For example, a decrease in water potential of blood is detected by osmoreceptors in hypothalamus, which stimulates ADH release from pituitary gland to increase the permeability of the wall of the collecting ducts in the kidneys. Therefore a large proportion of water is reabsorbed from fluid to prevent a fair proportion of water from being excreted.