In the renal system, peritubular capillaries are tiny blood vessels, supplied by the efferent arteriole, that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron. 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.
The majority of exchange through the peritubular capillaries occurs because of chemical gradients osmosis and hydrostatic pressure. Movement of water into the peritubular capillaries is due to the loss of water from the glomerulus during filtration, which increases the colloid osmotic pressure of the blood. 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. Other ions can be taken up by the peritubular capillaries via solvent drag. Water is also driven into the peritubular capillaries due to the higher fluid pressure of the interstitium, driven by reabsorption of fluid and electrolytes via active transport, and the low fluid pressure of blood entering the peritubular capillaries due to the narrowness of the efferent arteriole.
- Lote, Christopher J. (2012). Principles of Renal Physiology, 5th edition. Springer. p. 28.
- Mescher, Anthony L. (2016). Junqueira's Basic Histology, 14th edition. Lange. p. 394.
- Histology image: 16016loa – Histology Learning System at Boston University
- Nosek, Thomas M. "Section 7/7ch03/7ch03p10". Essentials of Human Physiology. Archived from the original on 2016-03-24. - "Renal Vasculature: Efferent Arterioles & Peritubular Capillaries"
- Anatomy photo: Urinary/mammal/vasc0/vasc4 - Comparative Organology at University of California, Davis - "Mammal, renal vasculature (EM, Low)"