Chapter 16 - Urinary System
The urinary system (also known as the renal system) consists of the kidneys, ureters, urinary bladder, and the urethra. Its main function is the production, storage, and expulsion of urine.
The kidney is involved in the formation of urine and regulation of pressure, volume, and pH of blood.
Nephrons are the structural and functional unit of the kidney. Each nephron includes a filter, called the renal corpuscle, and a single, long tubule through which the filtrate passes before emerging as urine.
The renal corpuscle contains the filtration apparatus of the kidney. It consists of a glomerular tuft of capillaries surrounded by Bowman's capsule.
The glomerular filtration barrier consists of three components:
- Endothelium of glomerular capillaries
- Glomerular basement membrane
- Filtration slit diaphragm between pedicels (or foot processes) of podocytes
The endothelium of the glomerular capillaries possess numerous fenestrations.
Podocytes are cells in Bowman's capsule that wrap around the capillaries of the glomerulus.
The renal tubules of a nephron consist of a proximal tubule, loop of Henle, and distal tubule.
Despite their relatively small size, the kidneys receive almost 20% of the cardiac output.
The urinary bladder is a muscular sac that stores urine, allowing urination to be infrequent and voluntary. It is lined by transitional epithelium (urothelium).