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Inner Zone of Renal Medulla
Kidney Lobe

Inner Zone of Renal Medulla

Zone interna medullae renalis

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Quick Facts

The inner zone of the medulla is the part of the renal medulla farthest in from the cortex, containing the innermost part of the loop of Henle and of the medullary collecting tubule (Dorland, 2011).

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Structure and/or Key Features

The inner zone of the renal medulla primarily consists of the descending and ascending thin limbs of the nephron loop, medullary collecting ducts, straight arterioles, and peritubular capillary bed. Straight arterioles tend to be absent near the tips of the renal papillae. Proximal and distal straight tubules are typically only found in the outer medulla (Dudek, 2006).

Unlike the striated appearance of the outer medulla, the inner medulla has more of a homogenous appearance, which tapers down to a blunt point before projecting into the pelvis of the ureter (Moffat, 1975).

Anatomical Relations

The inner zone of the renal medulla surrounds the renal pelvis and lies subjacent to the outer zone of the renal medulla.


The hypertonic environment of the inner medulla compared to the glomerular filtrate facilitates the reabsorption of water (Pocock et al, 2013).


Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.

Dudek, R. W. (2006) High-yield KidneyLippincott Williams & Wilkins.

Moffat, D. B. (1975) The Mammalian KidneyCambridge University Press.

Pocock, G., Richards, C. D. & Richards, D. A. (2013) Human Physiology, 4 edition. OUP Oxford.

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