The nephron is the functional unit of the kidney, it is comprised of the renal corpsucle (glomerulus and surrounding Bowman’s capsule) and renal tubule.
We shall first consider the glomerulus. This is a ball of capillaries surrounded by the Bowman’s capsule into which urine is filtered. The filtration barrier consists of three components: the endothelial cells of glomerular capillaries, the glomerular basement membrane and podocytes of the Bowman’s capsule.
The renal tubule can be divided into components, beginning with the proximal convoluted tubule. In this section the majority of the water, potassium, chloride and sodium that was filitered are reabsorped, as well as all of the glucose and amino acids.
The middle section is known as the Loop of Henle, it has a hairpin configuration with a thin descending limb and both a thin and thick ascending limb. In the thin descending limb water reabsorption occurs. Then sodium reabsorption occurs in the two parts of the ascending limb – this is both active and passive.
The distal convoluted tubule (DCT) and collecting duct (CD) are the final two segments of the kidney nephron. They have an important role in the absorption of many ions, and in water reabsorption. The distal convoluted tubule can be subdivided into two distinct regions, the early and late sections. The collecting duct also plays an important role in urea recycling.