The adrenal gland is composed of an outer cortex and inner medulla. The cortex develops from intermediate mesoderm and is divided into three concentric layers - the zona glomerulosa, zona fasciculata and zona reticularis. Each layer secretes different hormones - aldosterone from the glomerulosa, cortisol from the fasciculata and sex hormones from the reticularis. The medulla develops from neural crest cells and contains chromaffin cells that secrete epinephrine or norepinephrine into membrane-bound granules. Glucocorticoids stimulate the conversion of norepinephrine to epinephrine in the medulla.

1. Adrenal (Suprarenal) Gland
R. Kalliecharan

2. Embryology and Location
One lies superior to each Kidney
Each is composed of an outer region, the
Cortex and an inner region, the Medulla
Cortex is derived from intermediate
mesoderm whereas the Medulla is derived
from neural crest cells

4. Blood Supply
Several arteries supply blood to adrenals.
They form a subcapsular plexus from which arise
3 groups of vessels
1. arteries of capsule,
2. arteries of cortex which form capillaries in the
cortex. These enter into the medulla .
3. arteries of medulla which form capillaries in the
medulla. Thus, medulla has a dual blood supply.
The medullary veins that form join to form the
adrenal vein

6. Histology of Cortex
• Cortex has 3 concentric layers :
• A) zona glomerulosa , beneath capsule , is
composed of columnar or pyramidal cells and
arranged as rounded or arched cords
• B) zona fasciculata ( the middle layer),cells are
arranged in straight cords ,1 or 2 cells thick and
perpendicular to the surface.
• C) zona reticularis, cells arranged in an
anastomosing network. Lipofuscin granules and
pyknotic nuclei are present

10. Hormones of Cortex
• Glomerulosa cells secrete the
mineralocorticoid hormone---aldosterone
under control of angiotensin II
• Fasciculata cells secrete glucocorticoids---
cortisol under control of ACTH
• Reticularis cells secrete mainly steroid sex
hormones (dehydroepiandrosterone) under
control by ACTH

12. Hormones
Cells from Cortex do not store their hormones
in membrane-bound granules.
They syn and secrete only on demand.
They can diffuse freely across the P M since
they are steroids
Collaboration occurs between SER and Mito
in the production of steroidal hormones

18. Histology of Adrenal Medulla
• Composed of cords or clumps of cells called
chromaffin cells.These can acquire a brown color
which is due to oxidation of catecholamines by
chromic salts
• Chromaffin cells are modified sympathetic
postganglionic neurons without processes. Cells
are surrounded by capillaries
• Cells have lots of membrane-bound secretory
granules with either epinephrine or norepinephrine

20. Histology-Medulla
• Epinephrine secreting cells (80%) have smaller
granules that are less electron dense
• Norepinephrine secreting cells (20%) have larger
granules and more electron dense ; an electron –
lucent layer is present
• Catecholamine hormones are syn from tyrosine.
Norepinephrine that is formed leaves the granule
to enter cytosol
• Glucocorticoids transported from cortex to
medulla via cortical capillaries stimulates syn of
phenylethanolamine N- methyltransferase(PNMT)
to convert norepinephrine to epinephrine