Renal cortex
Cortex renalis
The outer, granular, reddish-brown layer of the kidney parenchyma (≈1 cm thick) containing the renal corpuscles, convoluted tubules and cortical collecting ducts; it also extends between the pyramids as renal columns.
Overview
The cortex lies beneath the fibrous capsule and arches over the bases of the renal pyramids. It has a granular appearance because it contains all the renal corpuscles (glomeruli), together with the proximal and distal convoluted tubules, connecting tubules and cortical collecting ducts, and a dense peritubular capillary network. It extends inward between the pyramids as the renal columns. Radially arranged medullary rays — bundles of straight tubules and collecting ducts that extend up from the medulla — divide the cortex into lobules; the convoluted parts between rays form the cortical labyrinth.
The cortex receives ≈90% of renal blood flow, has a high PO₂ and performs most of the bulk reabsorption (PCT) of the kidney. The outer cortex contains the glomeruli of cortical nephrons; the inner (juxtamedullary) cortex contains the larger glomeruli of juxtamedullary nephrons.
- Location
Between the fibrous capsule and the bases of the renal pyramids; also forms the renal columns.
Anatomy
- Arterial supply
Cortical radiate (interlobular) arteries arising from the arcuate arteries at the corticomedullary junction → afferent arterioles → glomeruli → efferent arterioles → peritubular capillaries.
- Histology
Renal corpuscles (≈200 µm), PCT (eosinophilic, brush border, indistinct cell borders), DCT (paler, no brush border, more nuclei per section), medullary rays and peritubular capillaries.
Function
- Glomerular filtration (all renal corpuscles are cortical)
- Bulk tubular reabsorption and secretion (PCT, DCT)
- Site of the juxtaglomerular apparatus (renin) and 1α-hydroxylation of vitamin D (PCT)
- Erythropoietin production by peritubular interstitial cells of the deep cortex
Clinical significance
Diffuse cortical necrosis
Rare, catastrophic ischaemic necrosis of the cortex (e.g. placental abruption with DIC, septic shock) that spares a subcapsular rim and juxtamedullary zone; often irreversible.
Cortical thinning on ultrasound
Small, echogenic kidneys with thin cortex indicate chronic kidney disease; normal-sized kidneys favour an acute process (exceptions: diabetes, amyloidosis, ADPKD, HIV nephropathy).
Compiled from standard anatomy and physiology references — see the Urinary System sources. For education only; not medical advice.