Quick Facts
The macula densa is a zone of compact, heavily nucleated cells located in the convoluted tubule of the kidney, where it makes contact with the vascular end of the glomerulus; it is closely associated anatomically with the juxtaglomerular cells of the afferent arteriole (Dorland, 2011).
Related parts of the anatomy
Structure and/or Key Feature(s)
The juxtaglomerular complex includes the macula densa, and the juxtaglomerular and mesangial cells.
The distal straight tubule traverses the medulla into the cortex within a medullary ray and aligns itself adjacent to the vascular pole of the renal corpuscle with which it is a component. A clustering of nuclei of epithelial cells lining the distal straight tubule directly adjacent to the afferent arteriole close to the vascular pole of the renal corpuscle form the “macula densa.”
Smooth muscle cells of adjacent afferent, and sometimes efferent, arterioles exhibit spherical nuclei and their cytoplasm contain secretory granules.
Function
The juxtaglomerular apparatus regulates blood pressure by activating the renin-angiotensin-aldosterone system. It also sensors blood volume and tubular fluid composition. The macula densa monitors Na+ concentration within the tubular fluid and regulate glomerular filtration rate and the release of renin from the juxtaglomerular cells (Ross and Pawlina, 2006).
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Ross, M. H. and Pawlina, W. (2006) Histology: A text and atlas. Lippincott Williams & Wilkins.
