Where is juxtaglomerular apparatus located

The juxtaglomerular apparatus, located in the glomerular hilum, consists of a vascular component afferent and efferent arterioles and extraglomerular mesangium and a tubular component macula densa. Two types of contact between vascular and tubular components are observed: a a complex type, involving distal tubule, extraglomerular mesangium, and proximal efferent arteriole, and b a simple type, consisting of apposition of the basement membranes of the vascular and tubular components.

Juxtaglomerular granular cells, the source of renin, are present throughout the vascular component but are more numerous in the afferent arteriole. They can be considered as "myoendocrine" cells, since they contain myofibrils and attachment bodies, together with secretory granules and crystalline protogranules. Juxtaglomerular apparatus en Espanol. Juxtaglomerular apparatus en Francais.

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Michael Gibson, M. The juxtaglomerular apparatus is a microscopic structure in the kidney , which regulates the function of each nephron. The juxtaglomerular apparatus is named for its proximity to the glomerulus : it is found between the vascular pole of the renal corpuscle and the returning distal convoluted tubule of the same nephron.

This location is critical to its function in regulating renal blood flow and glomerular filtration rate. The three microscopic components of the apparatus are the macula densa , extraglomerular mesangial cells , and juxtaglomerular cells.

Juxtaglomerular cells JG cells, also known as granular cells are the site of renin secretion. The JG cells are found in the afferent arterioles of the glomerulus and act as an intra-renal pressure sensor.

Lowered pressure leads to decreased pressure on the JG cells, allowing them to swell. Renin then acts to increase systemic blood pressure while maintaining GFR via the renin-angiotensin system. The macula densa senses sodium chloride concentration in the distal tubule of the kidney and secretes a locally active paracrine vasopressor which acts on the adjacent afferent arteriole to decrease glomerular filtration rate GFR , as part of the tubuloglomerular feedback loop.

Water flows into the cell to bring the osmolarity back down, causing the cell to swell. When the cell swells, a stretch-activated non-selective anion channel is opened on the basolateral surface. ATP escapes through this channel and is subsequently converted to adenosine.

Adenosine causes constriction of the vascular smooth muscle cells of the afferent arteriole, reducing the amount of blood that reaches the nephron.

Mesangial cells are structural cells in the glomerulus that under normal conditions serve as anchors for the glomerular capillaries. The macula densa segment of the distal tubule is characterized by closely packed nuclei, the basal or lateral position of the Golgi apparatus, and dispersed mitochondria that show little association with the reduced infoldings of the basal membrane.

In addition to these morphological differences, there are marked histochemical differences between the macula densa and the adjacent segments of the distal tubule.

Tubule-vessel contact appears to vary in extent and ultrastructure. The macula densa forms extensive and complex contact with the extraglomerular mesangial region. Contact with the arterioles may consist of simple apposition of basement membranes.