Short notes on the structure of the human kidney

Short notes on the structure of the human kidney

In human beings the kidneys are paired. They are bean shaped and are located between the levels of last thoracic and third lumbar vertebrae. The right kidney is placed slightly lower than the left because of the pres­ence of the liver.

The average size of the human kidney measures about 11 to 13 cms in length; 5 to 7.5 cms wide and 2.5 cms thick. In adults each weighs about 150 gms and this correspondence to about 1% of the body weight. The medial border of the kidney is slightly concave and has a marked depres­sion.

A long section of the kidney shows two main regions – an outer reddish cortex and an inner pale coloured medulla.

Cortex: The Cortex is granular in appearance because of the presence of convoluted uriniferous tubules. The cortex overlies the bases of the med­ullary apices called medullary pyramids. The cortex is also present be­tween the medullary pyramids. Under a magnifying glass the cortex can be seen divided into alternating radial tracks known as rays and laby­rinths. The rays are radially straight because they contain the straight parts of the uriniferous tubules. The Labyririths have a granular appear­ance because the tubules are cut irregularly.

Medulla: The medulla looks striated as the tubules run through it in a straight course. It consists of 10 to 15 conical masses called the renal pyramids. Two or three pyramids usually fuse and form the common apex called papilla. These papillae project into cup shaped channels known as calyces. The calyces join to form the pelvis which is the expanded initial part of the ureter.