Quick Facts
The outer zone of the medulla is the part of the renal medulla nearest to the cortex, containing part of the distal straight tubule and the medullary collecting tubule. It is subdivided into the inner stripe and the outer stripe (Dorland, 2011).
Related parts of the anatomy
Structure and/or Key Features
The outer zone of the renal medulla is distinct from the inner medulla due to the presence of specific portions of the renal tubule. Specifically, the outer medulla consists predominantly of proximal straight tubules, descending thin limbs of the nephron loop, ascending thin limbs of the nephron loop, distal straight tubules, medullary collecting ducts, straight arterioles, and a peritubular capillary bed. Proximal and distal straight tubules are typically only found in the outer medulla (Dudek, 2006).
The outer medulla is described as a richly vascular area, which in a longitudinal section, is recognizable by radially arranged striations that are representative of the vascular bundles.
Anatomical Relations
The outer zone of the renal medulla surrounds the inner zone of the renal medulla and lies subjacent to the cortex.
Function
The hypertonic environment of the outer zone of the renal medulla compared to the glomerular filtrate facilitates the reabsorption of water (Pocock et al, 2013).
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Dudek, R. W. (2006) High-yield KidneyLippincott Williams & Wilkins.
Pocock, G., Richards, C. D. & Richards, D. A. (2013) Human Physiology, 4 edition. OUP Oxford.
