Kidney is the main excretory organ of human body. This is called a body filter. In 1842, Sir William Bowman first explained the exact structure of the kidney. The structure of kidney can be described in two ways. External structure and internalization.
1. External Structure
Kidneys look like bean seeds and are reddish-brown in color. Its length is 10-12 cm, width is 5-6 cm and thickness is 3 cm. Male kidney weighs 125-170 grams and female kidney weighs 115-155 grams. Its outer side is convex and inner side is concave. The fold in the concave part is called Hilus. The hilus is attached to the ureter. Each kidney is covered by a fibrous connective tissue called the renal capsule or tunica fibrosa. Outside the renal capsule is a fatty layer that protects the kidney from friction. At the tip of the kidney are the cap-like adrenal glands.
2. Internal Structure
Three regions are seen in the longitudinal section of the kidney. These are-
(i) Cortex : The outermost layer of kidney wall is called cortex. It is divided into two parts. Supercial cortex and juxtamedullary cortex. The outer layer of the cortex is called the superficial cortex and the inner layer of the cortex is called the juxtamedullary cortex. The supracial cortex contains 85% and the juxtamedullary cortex 15% of nephrons. The cortex contains the renal corpuscle, proximal convoluted tubule, and distal convoluted tubule of the nephron.
(ii) Medulla: The central part of kidney wall is called medulla. It is light red in color. It consists of 8-18 pyramidal structures. It is called renal pyramid. The base of the pyramid faces the cortex and the apex faces the renal sinus. The top of the pyramid is called Papilla. Papilla with 10-25 pores. Apex of papilla opens into minor calyx. The minor calyxes open together into the major calyx. Also, the pillar-like part of the cortex between the two renal pyramids is called the Renal column. (iii) Pelvis: The large collecting space inside the kidney is called the pelvic floor. There are two types of branchial parts in the pelvis. There are 2-3 main branches. Major branches are called major calyxes. 8-14 minor calyxes arise from the major calyx.