Page 710 - Atlas of Histology with Functional Correlations

FIGURE 18.5 | Kidney Cortex: Juxtaglomerular

Apparatus

A higher magnification of the kidney cortex illustrates the renal corpuscle, the
surrounding convoluted tubules, and the juxtaglomerular apparatus.

In the middle is the renal corpuscle with glomerular capillaries (5),
parietal (8a) and visceral (8b) layers (epithelium) of the glomerular
(Bowman) capsule (8), and the capsular space (10) around the glomerulus.
Surrounding the renal corpuscle are the proximal convoluted tubules (7) with
brush borders and acidophilic cells. These tubules are distinguished from the

distal convoluted tubules (1, 6) that exhibit smaller and less intensely stained
cells that lack the brush borders. In contrast to the convoluted tubules, the
cuboidal cells of the collecting tubule (11) exhibit pale cytoplasm and distinct

cell outlines. Basement membrane (12) surrounds the collecting tubules (11).

Each renal corpuscle exhibits a vascular pole where the afferent glomerular
arteriole (4) enters and the efferent glomerular arteriole exits the renal
corpuscle. Inside the renal corpuscle, the glomerular arteriole forms a network of
glomerular capillaries (5). On the opposite side of the vascular pole is the

urinary pole (9). Here, the capsular space (10) becomes continuous with the
lumen of the proximal convoluted tubule (7). The plane of section through both
the vascular and urinary poles is only occasionally seen in the kidney cortex.
This illustration shows the glomerular arteriole (4) on one end and the urinary

pole (9) at the opposite end of the renal corpuscle.

At the vascular pole, modified epithelioid cells with cytoplasmic granules
replace the smooth muscle cells in the tunica media of the afferent glomerular
arteriole (4). These cells are the juxtaglomerular cells (3). In the adjacent distal

convoluted tubule, the cells next to the juxtaglomerular cells (3) are narrow and
more columnar and exhibit a more compact cell arrangement. This region in the
distal convoluted tubule is called the macula densa (2). The juxtaglomerular cells
(3) in the afferent glomerular arteriole (4) and the macula densa (2) cells in the

distal convoluted tubule form the juxtaglomerular apparatus.

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