The kidney is an organ that maintains water balance and expels metabolic wastes. In humans, They are bean-shaped structures located on either side of the backbone and are protected by the ribs and muscles of the back. Each human adult kidney has a length of 10-12 cm, a width of 5-7 cm, and weighs around 120-170g. Each kidney contains 1,000,000–1,250,000 nephrons that filter the entire five-quart water content of the blood every 45 minutes—an equivalent of 160 quarts a day. Of this, only 1 1/2 quarts are excreted; the remainder is reabsorbed by the nephrons.
Structure of Kidney
The structure of the kidneys is explained below:
- Capsule: The outer layer is called the capsule. Inside the kidneys, there are two zones- the outer zone is the cortex and the inner zone is the medulla. The cortex extends in between the medullary pyramids as renal columns called columns of Bertin.
- Nephrons: Nephrons are the functional units of the kidneys. Each nephron has two parts- glomerulus and renal tubule. Glomerulus consists of a bunch of capillaries formed by afferent arterioles. Blood from glomerulus is carried away by efferent arterioles. The renal tubule starts with a cup-like structure called Bowman’s capsule and this encloses the glomerulus. The malpighian body consists of glomerulus and Bowman’s capsule. The highly coiled structure in the tubule next to the Bowman’s capsule is the proximal convoluted tubule.
Renal physiology is the study of kidneys function. Nephrology is the medical specialty that addresses diseases of kidney function: these include chronic kidney disease, nephritic and nephrotic syndromes, acute kidney injury, and pyelonephritis. Urology addresses diseases of kidney (and urinary tract) anatomy: these include cancer, renal cysts, kidneys stones, and ureteral stones, and urinary tract obstruction.