There are two kidneys in the human body. They are place by both side of spine under the rib cage. Each kidney is of 10 to 12 cm long, 5 to 7 cm wide and of 120 to 170 g of weight in an normal adult.
Kidney main function is to filter the blood, remove waste products and maintain normal homeostasis of the body.
Structure of kidney
There are four main parts of the kidney,
- Renal cortex
- Renal medulla
- Renal pelvis
- Nephron
Renal cortex
Renal cortex is outer layer of the kidney. It is of reddish brown color. It contain glomeruli, bowmans capsule, nephrons in it.
Renal medulla
Renal medulla is the inner layer of kidney after renal cortex. It has renal pyrimids of cone shaped that is responsible for filtration of blood. These pyramids has millions of small vessels in it to filter out and concentrate urine. There are of 8 to 18 renal pyramids in each kidney.
Renal medulla consist of renal pyramids, nephrons, loop of henle, collecting duct, vasa recta and renal papillae.
Nephron
Nephron is the structural and functional unit of kidney. It start from renal corpuscles of glomerulus then bowmans capsule, renal tubule (PCT, loop of henle, DCT). The primary function of nephron is to recieve blood, then to filter to properly, reabsorb all vital elements and finally forms the waste product that is urine.
Renal Pelvis
Renal pelvis is located at the center of kidney, it is of funnel shaped cavity which functions as to collect urine from major vessels. The urine is further transport to the bladder via ureter.
Functions of the kidney
Kidney primary function is to filter blood, other functions are,
To excrete waste product from the body
Kidney is responsible for removing the uric acid, urea and toxic material that forms during normal body processes.
To maintain water level in the body during dehydration
When body goes into the dehydration then kidney reabosorb most of the water from renal tubule, as stimulated by hormones. As when dehydration ends then again kidney excrete excess water and maitain water balance through osmosis.
To maintain blood pressure
When blood pressure of the body decreases, kidneys produce renin enzyme which stimulates the contraction of blood vessels and retain salt from excreting out. This helps to maintain blood pressure.
To maintain red blood cell production
During hypoxia, Oxygen level drops, kidneys form erythropoietin hormone which stimulate more RBC production called as erythropoiesis. So, kidney is also responsible for maintaining the production of RBC.
To regulate electrolyte imbalance & maintain Ph balance of blood
Kidney regulate electrolytes such as sodium, potassium, calcium, chloride, phosphage, magnesium etc. When any one of electrolyte excess it excrete and in low amount it reabsorb it.
It also maintain acid base balance via regulating hydrogen ion (H⁺). and bicarbonate (HCO₃⁻), to maintain blood pH of 7.35 to 7.45.