Juxtamedullary nephron
Nephronum juxtamedullare
Also known as: long-looped nephron
A nephron (≈15%) whose large glomerulus lies near the corticomedullary junction and whose long loop of Henle penetrates deep into the inner medulla; its efferent arteriole forms the vasa recta. These nephrons build the medullary osmotic gradient.
Overview
Juxtamedullary nephrons have larger glomeruli with higher single-nephron GFR, located in the inner third of the cortex. Their loops of Henle descend into the inner medulla, sometimes to the papillary tip, and include a long thin descending limb, a thin ascending limb and a thick ascending limb. Their efferent arterioles give rise both to some peritubular capillaries and to the long hairpin vasa recta that run alongside the loops.
The length of the loop determines the maximum concentrating ability: species living in deserts (e.g. the kangaroo rat) have very long loops and can produce urine of >5000 mOsm/kg, whereas humans, with ≈15% long loops, reach ≈1200 mOsm/kg. Juxtamedullary nephrons are therefore essential for countercurrent multiplication and urine concentration.
- Location
Glomeruli in the inner cortex near the corticomedullary junction; loops reaching the inner medulla/papilla.
Anatomy
- Arterial supply
Efferent arterioles → vasa recta (and some peritubular capillaries).
Function
- Generate the corticomedullary osmotic gradient (countercurrent multiplier)
- Enable production of concentrated urine
Test yourself
Which feature distinguishes juxtamedullary nephrons from cortical nephrons?
- Their glomeruli lie in the outer cortex
- They lack a thick ascending limb
- They have long loops reaching the inner medulla and their efferent arterioles give rise to the vasa recta
- They make up about 85% of all nephrons
Answer: They have long loops reaching the inner medulla and their efferent arterioles give rise to the vasa recta
Juxtamedullary nephrons (≈15%) have glomeruli near the corticomedullary junction, long loops with thin ascending limbs extending to the papilla, and efferent arterioles forming the vasa recta — they create the medullary osmotic gradient.
Compiled from standard anatomy and physiology references — see the Urinary System sources. For education only; not medical advice.