Adrenal (Suprarenal) Gland

Adrenal (Suprarenal) Gland

R. Kalliecharan

Embryology and Location

One lies superior to each KidneyEach is composed of an outer region, the

Cortex and an inner region, the MedullaCortex is derived from intermediate

mesoderm whereas the Medulla is derived from neural crest cells

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

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 andperpendicular to the surface.

• C) zona reticularis, cells arranged in an anastomosing network. Lipofuscin granules and pyknotic nuclei are present

Hormones of Cortex

• Glomerulosa cells secrete the mineralocorticoid hormone---aldosteroneunder 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

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 steroidsCollaboration occurs between SER and Mito

in the production of steroidal hormones

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 secretorygranules with either epinephrine or norepinephrine

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