Longitudinal section through Kidney
This specimen shows the internal features of kidney.
The kidneys are a pair of bean-shaped excretory organs located in the posterior abdominal wall on either sides of the vertebral column. Each kidney is covered by a capsule. Inside the capsule, the substance of the kidney is divided into a paler outer cortex and a darker inner medulla. The medulla is aggregated in the form of pyramidal structures, known as the renal pyramids. The renal columns intervene between the renal pyramids. The other structures identified in this specimen are the renal papilla, the minor calyx, the major calyx, the renal pelvis and the renal sinus. The renal calculi can be formed anywhere along the calyces and the renal pelvis.
The capsule is made up of connective tissue. It covers the entire kidney. Medially, it enters the kidney through the hilum to line the renal sinus.
The renal cortex consists of the parts of the nephrons, namely, the Bowman‚Äôs capsule with the glomerulus, the proximal convoluted tubules, the distal convoluted tubules and the collecting tubules.
The renal medulla is made up of several pyramidal structures known as the renal pyramids. The Henle‚Äôs loop of the nephrons is located within the pyramids. Medullary rays extend from the bases of the pyramids towards the capsule through the renal cortex. Apex of the renal pyramids is directed medially towards the hilum.
The apices of the renal pyramids is known as the renal papillae.
A few renal papillae open into the cup-shaped minor calyx.
Several minor calyces open into the major calyx.
The renal pelvis is the initial part of the ureters. Renal pelvis is formed by the coalescence of two to three major calyces within the kidneys and extends up to the lower poles of the kidneys. Thereafter, the renal pelvis continues as the ureters.
The space within the hilum is known as renal sinus. It is lined by the renal capsule. It is filled with perirenal fat. It is occupied by the renal vein, the renal artery and the renal pelvis.