Peritubular capillaries
Vasa capillaria peritubularia
Also known as: peritubular capillary network
The low-pressure capillary network derived from efferent arterioles that surrounds the cortical tubules, taking up reabsorbed fluid and supplying solutes for secretion.
Overview
After leaving the glomerulus, blood in the peritubular capillaries has a low hydrostatic pressure (≈10–20 mmHg) and a high oncotic pressure (≈32–35 mmHg, because ≈20% of plasma water was just filtered while proteins remained) — Starling forces that strongly favour uptake of the fluid reabsorbed by the tubules. Changes in these forces link glomerular filtration to proximal reabsorption (glomerulotubular balance): when the filtration fraction rises, peritubular oncotic pressure rises and more fluid is reabsorbed.
The capillaries are fenestrated and lie closely applied to the basolateral surface of the PCT and DCT, delivering substrates (organic anions, cations, drugs) for tubular secretion. Interstitial fibroblast-like cells between these capillaries in the deep cortex secrete erythropoietin in response to hypoxia. They drain into cortical radiate (interlobular) veins.
- Location
Renal cortex, around proximal and distal convoluted tubules.
Function
- Return reabsorbed water and solutes to the circulation
- Supply substances for tubular secretion
- Provide O₂ and nutrients to the cortical tubules
- Site of oxygen sensing and EPO production by adjacent interstitial cells
- Physiology
Hydrostatic pressure ≈13 mmHg vs oncotic ≈32 mmHg → net reabsorptive force ≈10 mmHg or more.
Clinical significance
Peritubular capillary loss in CKD
Rarefaction of peritubular capillaries with interstitial fibrosis causes tubular hypoxia, progressive nephron loss and reduced EPO production (anaemia of CKD).
Compiled from standard anatomy and physiology references — see the Urinary System sources. For education only; not medical advice.