Hypertension and nephrology

[The apparatus which controls our kidney too. Part 2 - Structure and function of the juxtaglomerular apparatus]

ROSIVALL László

DECEMBER 30, 2012

Hypertension and nephrology - 2012;16(06)

[The juxtaglomerular apparatus is comprised of the macula densa (a specialregion of the distal tubule), the renin producing granular or epithelioid-cells of the afferent arteriole, the extraglomerular mesengial cells, and the efferent arteriole’s section bordering this region. Somewhat more general definitions also exist. Recently, distinctive morphological and functional associations have been identified between the components of the JGA and some common mediators (e.g. adenosine, angiotensin, NO, prostaglandins, etc.). Current data suggest that each cell of the macula densa also contain few cilia that may have a role in sensing fluid flow. The distal section of the afferent arteriole (possessing the same structure as the glomerular capillaries) is covered by fenestrated endothelium. Trace dose of ferritin particles can pass through the afferent arteriole’s fenestrae into the interstitium of the JGA due to the considerable hydrostatic pressure gradient. The parietal lamina of Bowman’s capsule, which covers the renin granulated cells of the afferent arteriole behaves much like the visceral lamina in that the epithelial cells of the parietal lamina exhibit foot processes and filtration slits. The urinary space is regularly bulging into the extraglomerular mesangium. Therefore, the notion has been refuted that the JGA, which contains neither blood nor lymph capillaries, is a closed system engaging in only slow fluid exchange. Furthermore it is affirmed that the afferent arteriole consists of two morphologically and functionally disparate segments, the ratio of which is considerably modified by the activity of the renin-angiotensin system.]

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