Peritubular capillaries surround the cortical parts of the proximal and distal tubules, while the vasa recta go into the medulla to approach the loop of Henle.

Essentially, the peritubular capillaries reabsorb useful substances such as glucose and amino acids and secrete certain mineral ions and excess water into the tubule.

The majority of exchange through the peritubular capillaries occurs because of chemical gradients osmosis and hydrostatic pressure.

This blood leaves the glomerulus via the efferent arteriole, which supplies the peritubular capillaries.

The higher osmolarity of the blood in the peritubular capillaries creates an osmotic pressure which causes the uptake of water.