2. IN THIS LECTURE WE WILL LEARN ABOUT
• Organization of the adrenal stroma
• Organization of the adrenal parenchyma
• Medulla
• Cortex
• Functions of adrenal gland products
3. The suprarenal glands are retroperitoneal paired structures related to the superior
pole of each kidney. They are highly vascular solid organs surrounded by a thick
connective tissue capsule whose trabeculae reach the deep cortex.
• Blood through the gland flows from
the capsule through the cortex to
the medulla
• Capsular arterioles → cortical
sinusoids/fenestrated capillaries →
medullary sinusoids
• The medulla receives oxygenated
blood via medullary arterioles
• Drainage of blood is to
adrenomedullary collecting veins
→ central adrenomedullary vein
that forms the adrenal vein
4. The parenchyma of the adrenal gland is divided into
a thick peripheral cortex forming most of the gland
and a central region, the medulla (10% by mass).
• The medulla consists of clusters and short
cords of cells separated by wide venous
sinusoids in a reticular meshwork
• Chromaffin cells are large pale staining cells of
neural crest origin and are modified neurons
• Synthesize store and secrete catecholamines
• Adrenaline secreting cells > noradrenaline
secreting cells
• Form single rows along venous sinusoids
• Contain large nuclei, basophilic cytoplasm, rER and
well developed Golgi bodies
• Contain numerous secretory vesicles
• Presynaptic sympathetic terminals synapse directly
on chromaffin cells to trigger catecholamine
release
5. The parenchyma of the adrenal gland is divided into
a thick peripheral cortex forming most of the gland
and a central region, the medulla (10% by mass).
• Glucocorticoids of the adrenal cortex
promote conversion of noradrenaline to
adrenaline in chromaffin cells
• Ganglion cells in the medulla are a type of
sympathetic postganglionic neuron whose
axons penetrate the adrenal cortex
6. The cortex of the adrenal gland is organized in 3 zones distinguished by the organization of cells: zona
glomerulosa (15% of cortical volume), zona fasciculata (80% of cortical volume and zona reticularis (5% of
cortical volume). The zones are made up lipid synthetic cells that may be distinguished further on the basis of
enzymatic activity.
• Zona glomerulosa cells are small
and organized in ovoid clusters
• Secrete the mineralocorticoid
aldosterone
• Aldosterone synthesis from
cholesterol requires aldosterone
synthase
• Aldosterone synthase activity is
regulated by angiotensin II
7. The cortex of the adrenal gland is organized in 3 zones distinguished by the organization of cells: zona
glomerulosa (15% of cortical volume), zona fasciculata (80% of cortical volume and zona reticularis (5% of
cortical volume). The zones are made up lipid synthetic cells that may be distinguished further on the basis of
enzymatic activity.
• Zona fasciculata cells are large and
arranged in long cords two cells thick
separated by sinusoids and
continuous with the clusters of ZG
• Secrete the glucocorticoids cortisol and
corticosterone
• And small amounts of gonadocorticoids
• Corticosteroid synthesis requires 17 α
hydrolase
• Corticosteroid synthesis is regulated by
ACTH, in turn regulated by CRH
• Feedback via corticosteroid levels is on CRH
activity
• Corticosteroid levels can promote CRH
activity via higher cortical centers
• The deep zona fasciculata thickens in
pregnancy and atrophies with age
8. The cortex of the adrenal gland is organized in 3 zones distinguished by the organization of cells: zona
glomerulosa (15% of cortical volume), zona fasciculata (80% of cortical volume and zona reticularis (5% of
cortical volume). The zones are made up (variably basophilic) lipid synthetic cells that may be distinguished
further on the basis of enzymatic activity.
• Zona reticularis has small cells
arranged in anastomosing cords
separated by sinusoids
• Secrete gonadocorticoids /adrenal
androgens
• DHEA, DHEAS, androstenedione
• Small amounts of glucocorticoids
• Conversion of androstenedione to
testosterone in women may cause
masculinization
• Gonadocorticoid synthesis is
regulated by ACTH, in turn regulated
by CRH
9. The fetal adrenal gland is an important source of steroid hormones and component of the
fetoplacental unit. At its peak size (month 4) it is nearly the size of the kidney and produces adult
doses of steroids at term. Most of this additional mass is restricted to the fetal cortex/zone which
makes up 80% of the gland. The definitive cortex and medulla emerge postnatally with agenesis of
the fetal cortex.
