QS Study

Structure of the Kidney

Our kidneys cooperate numerous essential roles in maintaining your health. One of their most significant jobs is to clean waste materials from the blood and eject them from the body as urine. The primary function of the kidneys is to sustain the accurate stability of water and minerals in the body.

Kidneys are bean-shaped organs, about 11 cm long, 6 cm wide, 3 cm thick and weigh 150 g. They are embedded in and held in position by, a mass of adipose tissue. They are located at the back of the abdominal cavity, one on each side of the spine. Each kidney weighs 125 to 170 grams (g) in males and 115 to 155 g in females.

(1) Nacked eye examination

A coronal section of the kidney shows:-

a) an outer reddish brown cortex.

b) an inner pale medulla.

c) space, the renal sinus.

Fig: Structure of the Kidney

Renal medulla:

The renal medulla is the smooth, inner tissue of the kidney. It contains the loop of Henle as well as renal pyramids. The renal medulla is made up of about 10 conical masses, called the renal pyramides. Their apices from the renal papillae which indent the minor calyx.

Renal cortex:

The renal cortex is the outer part of the kidney. It contains the glomerulus and convoluted tubules. The renal cortex is divided into two parts –

(i) The cortical arches or cortical lobules which form caps over the bases of the pyramids.

(ii) The renal columns, which dip in between the pyramids. Each pyramid along with the overlying cortical arch forms a lobe of the kidney.

Renal sinus:

The renal sinus is a space that extends into the kidney from the hilus. It contains –

(a) Tributaries of the renal vein.

(b) Branches of the renal artery.

(c) The renal pelvis.

The pelvis divides into 2 or 3 major calyces and these divide into 7 to 13 minor calyces. Each minor calyx ends in an expansion which is indented by one to three renal papillae.

(2) Histologically

Each kidney is composed of one to three million uriniferous tubules. Each tubule consists of two parts –

(a) The secretary part, which forms urine is called the nephron. It is the functional unit of the kidney.

(b) Nephrons open into collecting tubules. Many such tubules unite to form the ducts of Bellini which open into the minor calyces through the summits of renal papillae.