Question

List the hormones secreted by the kidney.

Answer 1

Hint: Apart from performing the function of excretion, kidneys also regulate body fluid osmoregulation by controlling the amount of water and salts. Like any other cells in the body, its cells also require an optimal oxygen concentration for proper functioning.

Complete answer:
Along with excretion, kidneys also release certain hormones like renin and erythropoietin.
The juxtaglomerular apparatus or JGA releases renin in the bloodstream in response to a fall in glomerular filtration rate or GFR which is a result of a fall of NaCl and arterial blood pressure. Renin in the blood stimulates the conversion of angiotensinogen into angiotensin II. This hormone, in turn, stimulates the adrenal cortex to release aldosterone. Rate of sodium ions reabsorption by the nephrons increases when stimulated by aldosterone. This is referred to as the renin- angiotensin- aldosterone pathway.
When the amount of oxygen delivered to the kidney is below normal, the cells of the kidney produce erythropoietin. The site of action of erythropoietin is bone marrow where it induces erythropoiesis or red blood cells production.
The human excretory system has the following organs:
Kidneys - The paired kidneys are bean-shaped and reddish- brown. Both the kidneys bear a notch known as hilum from which blood vessels, lymph vessels, nerves and ureters enter or leave.
Ureter - They are paired, narrow, tubular structures which open into the urinary bladder.
Urinary bladder - It is a pear-shaped muscular sac found in the pelvic cavity. It temporarily stores urine. Urine exerts pressure on the inner walls of the urinary bladder when its volume exceeds 200- 400 mL activating the stretch receptors on its wall to urinate.
Urethra- It is a canal- like structure which spreads from the floor of the bladder to the exterior.

Note:
- Do not confuse Renin with Rennin where the former is secreted by the kidney and the latter is released by the peptic cells in the stomach.
- Renin is stimulated by a fall in GFR while Rennin is released due to the presence of milk protein ‘Casein’ and aids in its digestion.