The kidney is dark red bean shaped, body of the size of fist located in the posterior part of the body behind the peritoneal lining of the abodomen, below the diaphragm, protected by the lower ribs, on either side of the vertebral column. It is covered by tough renal capsule. Just like bean it has an identation known as pelvis.
The kidney consits of two regions. It consists of inner medulla covered by outer cortex. Pelvis is a hallow funnel like structures into whcih urine drains and is continued as ureter. The two kidneys have one ureter each, which joinsthe urinary bladder. From the urinary bladder the urine flows out through urethra.
Pelvis is divided into four to eight funnel shaped cups of which is called major calyx. Each major calyx receives urine fromt wo or more smaller minor calycees. Each minor calyx surrounds many papillae and each papilla has many pores which are the openings of collecting tubules. Renal medulla has many small regions called pyramids. Each pyamid is a cone shaped region ending in a small tip called Papillae. Many such tips or papillae open into a major calyx. It can be compared to nipple of the breast.
Nephron is the filtration unit of Kidney.Each kidney has about a million nephrons. Neprhron consists of 1 renal afferent artery and 2 bowmans capsule - renal afferent artery brings blood into a bowman capsule where it divides into small capillaries. These tuft of capillaries fill in the bowman's capsule. The plasma and the dissolved solutes like glucose, urea salts, gets filtered out of the capillaries. Blood cells and large protein molecules like globulins return through efferent artery that emerge out of the bowman capsule.
About one fourth of the cardiac output per minute reaches the kidney. The entire blood volume passes through kidneys once in 4 minutes. The glomerular filtrate formed ia about 125ml/mt. In about 24 hours about 180 L of filtrate is formed at the bowman capsules. The amount of urine formed per day is around 1.0-1.5L/day. The water in the filitrate is reabsorbed through renal tubules.