Extraglomerular mesangial cell
Histological appearance of the juxtaglomerular apparatus. A cross section through a thick ascending limb is on top and part of a glomerulus is below. The juxtaglomerular apparatus consists of the macula densa, extraglomerular mesangial cells, and granular cells. (From Taugner R, Hackenthal E. The Juxtaglomerular Apparatus: Structure and Function. Berlin: Springer, 1989.)
prised of the macula densa, extraglomerular mesangial cells, and granular cells (Fig. 23.4). The macula densa (dense spot) consists of densely crowded tubular epithelial cells on the side of the thick ascending limb that faces the glomerular tuft; these cells monitor the composition of the fluid in the tubule lumen at this point. The extraglomerular mesangial cells are continuous with mesangial cells of the glomerulus; they may transmit information from macula densa cells to the granular cells. The granular cells are modified vascular smooth muscle cells with an epithelioid appearance, located mainly in the afferent arterioles close to the glomerulus. These cells synthesize and release renin, a proteolytic enzyme that results in angiotensin formation (see Chapter 24).
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.