Kidney Parts

B. Nephrons: Nephrons are the functional subunits of the kidney.
Each includes a renal corpuscle, a proximal convoluted tubule, a loop of Henle, and a distal convoluted tubule.

1. Renal corpuscle. As the blood-filtering unit of the nephron, each renal corpuscle consists of a glomerulus covered by Bowman's capsule. Together these structures form the filtration barrier. Each corpuscle has both a urinary and a vascular pole.

a. Glomerulus, This is a small tuft of fenestrated capillaries. Modified smooth muscle cells, mesangial cells, lie between the capillary loops.

b. Bowman's capsule is a double-walled epithelial chamber. Its inner wall, or visceral layer, consists of podocytes, These cells have long primary processes, from which arise interdigitating foot processes (pedicels) that grasp the glomerular capillaries like fingers around a broom handle and adhere tightly to the fused capillary-podocyte basal lamina. The outer wall--the parietal layer--is simple squamous epithelium. The chamber between the visceral and parietal layers is known as the urinary or Bowman's space,

c. Filtration barrier. Consisting of the structures that separate the capillary lumen from the urinary space, the filtration barrier includes
(l)the diaphragm-covered capillary fenestrations,
(2) the fused basal laminae of the capillary endothelial cells and podocytes, and
(3) the diaphragm-covered filtration slits that lie between the interdigitating pedicels. d. Vascular pole. This side of the corpuscle is where the afferent arterioles that feed the glomerular capillaries enter and the efferent arterioles that drain them leave. It lies opposite the urinary pole.

e. Urinary pole. This side of the corpuscle is where the proximal convoluted tubule exits.