The renal corpuscle, also known as a Malpighian corpuscle, is the
essential portion of the nephron. It consists of a renal glomerulus and
Bowman's capsule. The corpuscle has two poles: the vascular pole and
urinary pole. At the vascular pole, the afferent arteriole (which
supplies the capillary network of the glomerulus) enters, and the
efferent arteriole (which collects the blood from the capillaries)
leaves the corpuscle. The urinary pole is the beginning of the proximal
convoluted tubule; it is continuous with Bowman's space.
The distal convoluted tubule is situated between
the straight part of the proximal tubule and the collecting tubule, and
is composed of a straight part and a distal convoluted part. The
epithelial cells lining the distal convoluted tubule are cuboidal, with a
round nucleus and basal striations at the base of the cells. The distal
convoluted tubule is responsible for the resorption of sodium, an
activity that is promoted by the hormone aldosterone. At the portion of
the distal convoluted tubule contacting the parent renal corpuscle
between afferent and efferent arterioles, the epithelial cells become
densely packed, with the nuclei close together. Thus the region appears
darker and is known as macula densa. The macula cells are immediately
adjacent to the afferent and efferent arterioles, to the juxtaglomerular
cells, and to the extraglomerular mesangial cells. These three cell
groups together are called the juxtaglomerular apparatus.