Question

What are kidneys?

Answer 1

A pair of kidneys, a pair of ureters, a urinary bladder, and a urethra make up the human excretory system. The kidneys are the primary organs through which the body removes toxins. The kidney's principal job is to remove waste from the bloodstream through the creation of urine. Kidneys also have a number of homeostatic functions, including:
1. Keeping the extracellular fluid volume constant.
2. Keeping the extracellular fluid ionic equilibrium.
3. Maintaining the extracellular fluid's pH and osmolarity.

Complete answer:
Kidneys are one of the most important organs in our bodies since they aid in the filtration of urine. In vertebrates, the kidneys are a pair of bean-shaped organs.
The reddish-brown bean-shaped organs that make up the kidneys are two in number. They are found in the retroperitoneal space on the left and right sides. Each kidney has a ureter, which is a tube that transports expelled urine to the bladder.
The kidneys are found high in the abdominal cavity, one on each side of the spine, in humans. The left kidney is roughly between $T12$ and $L3$ on the spinal column, while the right is slightly lower.
The kidney is a bean-shaped organ with a concave border and a convex surface. A number of waste materials are excreted by the kidneys into the urine. The Nephron is the kidney's functional and microscopic unit. Filtration, reabsorption, secretion, and excretion are all methods it uses to digest the blood it receives.
The acid-base balance, electrolyte concentrations, extracellular fluid volume, and blood pressure are all regulated by the kidneys, which contribute to overall body homeostasis.
Though the kidneys do not detect blood, they are completely responsible for long-term blood pressure management.

Note:
Erythropoietin, calcitriol, and renin are among the hormones secreted by the kidneys. Erythropoietin is a hormone that is generated in reaction to hypoxia in the renal circulation and stimulates erythropoiesis, or red blood cell formation in the bone marrow.
Renin is an enzyme that regulates the levels of angiotensin and aldosterone.