Brief note on the Microscopic Structure of the Kidney of Mammal

Kidney:

The kidneys are main excretory organ in rabbit. They are metanephric, bean-shaped and dark red in color, situated on the dorsal wall of the anterior end of the abdominal cavity outside the coelom. They lie asymmetrically on either side of the vertebral column and the right kidney is somewhat more anteriorly placed than the left kidney due to the presence of the stomach on the left side.

Each kidney is about 25 mm long. Its outer surface is convex and the inner surface is concave having a median notch, called hilus. From the hilus, the ureter runs back to open into the urinary bladder. The kidney gets blood supply through a renal artery entering the kidney at hilus and the blood comes out through a renal vein.

Microscopic Structure of the Kidney (L.S.):

In the longitudinal section, it is seen that the kidney is enclosed in a thin capsule of connective tissue. The kidney is differentiated into two regions, the outer cortex and inner medulla. The medulla is made of lobes called pyramids and the cortex is extended in between of pyramids in the form of renal columns called columns of Bertini.

The pyramids are connected with the pelvis or renal sinus, which is continued as ureter. The kidney is composed of a mass of fine tubules called uriniferous tubules or nephrons, which are about two lakhs in number. Each uriniferous tubule is formed of malpighian corpuscle and the tubular part.

Cortex:

The cortex is granular in appearance because here the tubules are much convoluted and it contains malpighian corpuscles which are always confined to it.

Medulla:

The medulla appears striated as it contains nonglandular part of the uriniferous tubules, which run through it in a straight way radiating towards the pelvis. In this region, the malpighian corpuseles are entirely absent only tubular part of rephrons are present in the medulla. The medulla consists of 10 to 15 conical masses, the renal pyramids, whose apices form the papillae. The papillae project into cup-shaped channels known as calyces. The calyces join to form the pelvis, which is the expanded beginning of the ureter.

Uriniferous tubules: These are structural and functional untis of the kidney. Each uriniferous tubule comprises two parts.

The secretory tubule, which is long and unbranched.

The excretory portion, which is, branched tree-like system of excretory ducts.