The kidneys have 3 main functions, which are explained in more detail in subsequent articles:
- Excretion of waste products
- Homeostasis of extracellular volume and composition
- Hormone production:
Kidneys are retroperitoneal organs that lie at levels T12 – L3 levels; the right kidney lies slightly lower than the left kidney because of displacement by the liver. They are surrounded by a thick protective fibrous capsule. The renal hilum lies on the medial aspect of the kidneys and is the entry site for the renal artery, renal vein and ureter, which are arranged in an anterior-to-posterior manner respectively.
Nephrons are the functional unit of the kidneys and are responsible for the filtration, resorption and secretion functions. They are composed of the renal corpuscle (formed by the) and renal tubules. The glomerulus and Bowman’s capsule form the corpuscle and are responsible for filtration. The tubules subsequently reabsorb from and secrete into the filtrate, whereupon the remaining ultrafiltered fluid is passed onto the collecting ducts to from urine, which then drains via the ureter to the bladder.
Renal arteries come off the abdominal aorta and branch to form afferent glomerular arterioles.
Supplied by nerves from spinal levels T10-11, so pain may be referred from the kidneys to the loins.