RS 3 Juxtaglomerular Apparatus - Coggle Diagram
Juxtaglomerular apparatus as the name indicates (juxta—near) refers to
collection of specialized cells located very near to the glomerulus.
It forms the major component of
The juxtaglomerular apparatus comprises three types of cells:
(JG) cells are specialized myoepithelial (modified
vascular smooth muscle) cells
located in the media of the afferent
arteriole in the region of juxtaglomerular apparatus.
They have well-developed
Golgi apparatus and endoplasmic
reticulum, abundant mitochondria and ribosomes.
They synthesize, store and release an enzyme called renin.
Renin is stored in the
secretory granules of JG cells and,
therefore, these are
also called granular cells.
They act as baroreceptors (tension receptors)
and respond to changes
in the transmural pressure gradient between the afferent arterioles
and the interstitium.
They are densely innervated by sympathetic nerve fibres
and release their renin content in response to sympathetic discharge.
act as vascular volume receptors,
they monitor renal
perfusion pressure and are stimulated by hypovolaemia or decreased
renal perfusion pressure.
The granulation of these cells increases
when there is sustained hypotension
in afferent arteriole,
in sodium deficiency.
Macula densa cells
Macula densa cells refer to the
specialized renal tubular epithelial cells
of a short segment of the thick ascending limb of loop of Henle which
passes between the afferent and efferent arterioles supplying its glomerulus of origin.
They are not well adapted for reabsorption.
They are not innervated.
They have prominent nuclei,
and their Golgi complex is usually
located between the nucleus and the cell base
(i.e. towards the afferent arteriole),
while in other tubular cells the Golgi complex is
located near the apical membrane.
These characteristics suggest that
these cells may be secreting a substance towards the arteriole.
These cells are in direct contact with the mesangial cells
and in close contact
with the juxtaglomerular cells.
They act as chemoreceptors .
and are stimulated by decreased NaCl
causing increased renin release
Mesangial cells or lacis cells are the
interstitial cells of the
They are in contact with both the macula densa cells (on one side)
and juxtaglomerular cells (on the other side).
these cells act as supporting cells and plugging device at the glomerular entrance.
these cells possibly relay the signals from macula densa to granular cells after modulating the signals.
In this way, a
decreased intraluminal Na+ load, Cl− load or both in the region of macula densa
stimulates the juxtaglomerular cells to secrete renin.
They also show granulation to secrete renin in conditions of
They also secrete various substances and take up immune complexes.