336
UNIT 3
â– 
Organ Systems
Zona reticularis
Zona reticularis
Zona reticularis
Zona fasciculata
Zona fasciculata
Zona fasciculata
Zona glomerulosa
Zona glomerulosa
Zona glomerulosa
Capsule
Capsule
Capsule
Cortex
Cortex
Cortex
Medulla
Medulla
Medulla
Cortex
Cortex
Cortex
Medulla
Medulla
Medulla
Fig. 17-10B
A
Zones of the adrenal gland
2
3
4
1
2
4
3
1
Zona reticularis
Zona reticularis
Zona reticularis
Medulla
Medulla
Medulla
Medulla
Medulla
Medulla
Zona reticularis
Zona reticularis
Zona reticularis
Zona reticularis
Zona reticularis
Zona reticularis
Zona fasciculata
Zona fasciculata
Zona fasciculata
Zona fasciculata
Zona fasciculata
Zona fasciculata
Zona glomerulosa
Zona glomerulosa
Zona glomerulosa
Zona glomerulosa
Zona glomerulosa
Zona glomerulosa
Capsule
Capsule
Capsule
Capillary
Capillary
Capillary
Capillary
Capillary
Capillary
Capillary
Capillary
Capillary
Capillaries
Capillaries
Capillaries
Cortex
Cortex
Cortex
B
Figure 17-10A.
Overview of the adrenal glands.
H&E,
3
7
An
adrenal gland
covers the apical region of each kidney. It is
also called the
suprarenal gland
(Fig. 17-1A). Each adrenal gland
is covered by a connective tissue
capsule
and has a
cortex
and a
medulla
. The
cortex
of the adrenal gland is derived from the
meso-
derm
and can be divided into three zones: the
zona glomerulosa
,
zona fasciculata
, and
zona reticularis
. Hormone-producing cells
in the cortex secrete several types of hormones:
mineralocor-
ticoids
,
glucocorticoids
, and
weak androgens
. The
medulla
of
the adrenal gland is derived from the
neural crest
and contains
cell bodies of
sympathetic ganglion neurons
and their axons as
well as
chromaf± n cells
, which synthesize and release
adrenaline
(
epinephrine
) and
noradrenaline
(
norepinephrine
) (Fig. 17-12A,B).
Figure 17-10B.
Cortex of the adrenal gland.
H&E, left
3
41, left (
insets
)
3
466; right (
4 panels
)
3
163
The
cortex
of the adrenal gland contains many glandular cells. These cells are arranged in cords, which are formed by hormone secretory
cells. The capillaries run parallel to these cords. (1) The
zona glomerulosa
lies beneath the connective capsule and consists of secretory cells
that contain lipid droplets (
vacuoles
) and a pale-staining cytoplasm. These cells are arranged in round or ovoid clusters (like glomeruli);
they secrete
mineralocorticoids
, mainly
aldosterone
, which control the electrolyte balance by acting on the distal tubules of the kidney to
increase Na
+
and decrease K
+
absorption. (2) The
zona fasciculata
contains hormone-secreting cells that secrete
glucocorticoids
(mainly
cortisol
and
corticosterone
). The glucocorticoids stimulate glycogen synthesis in the liver; increase carbohydrate, fat, and protein metabo-
lism; and suppress the immune response by slowing down immune cell (
lymphocyte
) circulation. ACTH stimulates the production of glu-
cocorticoids. The cells in the zona fasciculata contain many lipid droplets, which make the cytoplasm appear light and vacuolated. These
cells are arranged in long cords in which cell nuclei are packed close to one another with their pale-stained cytoplasm facing the capillaries.
(3) The
zona reticularis
is adjacent to the medulla. Its secretory cells contain only a few lipid droplets, and their cytoplasm is stained dark
and acidophilic in appearance. The cells are arranged in anastomosing cords, which are intermixed with by surrounding capillaries. These
secretory cells secrete
androgens
(mainly dehydroepiandrosterone), which can be converted into testosterone or estrogen. ACTH also
stimulates the secretion of the adrenal androgens. (4) The
junction
between the
zona reticularis
and the
medulla
is shown here. There are
many blood vessels separating the zona reticularis of the cortex and the medulla. The cells in the medulla are stained lighter than the cells
in the zona reticularis. The
left insets
show a high power view of hormone secreting cells in the zona glomerulosa, zona fasciculata, and
zona reticularis of the adrenal gland cortex. The
right panels
show regions of the adrenal gland that are indicated by the
dashed boxes
.
Adrenal Glands (Suprarenal Glands)
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