Kidneys

Hi, this post will discuss the anatomy of the kidneys including their anatomical features, innervation, lymphatic drainage and topographical anatomy. 



Anatomical Features 

The kidney can be divided into two sections. The outermost region is known as the cortex while the innermost region is termed the medulla. The cortex contains the glomeruli, proximal and distal convoluted tubules and many of the blood vessels of the kidney. The medulla is made up of the loop of Henle and the collecting tubules. A tough, fibrous, inelastic capsule covers the external surfaces of the kidney.

The outer surface of the kidney is smooth and convex in most species. There is an indentation on the medial border, however, and this opens into a space known as the renal sinus. The renal pelvis sits inside the renal sinus. Internally, the kidney is separated into sections, called renal columns or pyramids by interlobar arteries. The apex of the renal column forms the renal papilla that protrudes into the renal calyx in the sinus. The minor calyxes are cup-shaped dilations of the ureter within the kidney, they drain into major calyxes 

Urine passes from collecting tubules to papillary ducts which empty into calyxes and then to the renal pelvis. This then drains into the ureters. The renal sinus is lined with transitional epithelium.

Innervation

The kidneys receive parasympathetic and sympathetic innervation from the solar plexus. These nerves travel with the renal arteries into the kidneys. The sympathetic fibres synapse at the coeliac and cranial mesenteric ganglia. 

Lymph Drainage

Lymph drains from the kidneys into the renal lymph nodes.

Topography 

The kidneys are located in the caudo-dorsal region of the abdomen. They are asymmetrical with the right kidney being more cranial than the left in all species except the pig. Both kidneys are surrounded by renal fascia and perirenal fat which protects them from other organs. 

The right kidney is less mobile than the left as it is embedded in the renal fossa of the caudate lobe of the liver. Medial to the right kidney is the caudal vena cava and the right adrenal gland. The descending duodenum is found ventral to this kidney.

The cranial pole of the left kidney is in contact with the greater curvature of the stomach and the spleen. The left adrenal gland is near the medial aspect of the cranial pole. The caudal pole contacts the small intestine and descending colon.  Medial to the left kidney is the aorta. 

That's all for this post, see you next time :)