histology of adrenal glands

HISTOLOGY OF ADRENAL GLANDSPrepared by: Dr. Ahmed Mead

MD. USTPhD. CANDIDATE. OMU

GENERAL HEALTH SCIENCEHistology and Embryology(MEDICINE)

ADRENAL GLANDS

The adrenal (suprarenal) glands secrete both steroid hormones and catecholamines. They have a flattened triangular shape and are embedded in the perirenal fat at the superior poles of the kidneys.

The adrenal glands are covered with a thick connective tissue capsule from which trabeculae extend into the parenchyma, carrying blood vessels and nerves.

The secretory parenchymal tissue is organized into two distinct regions

• The cortex is the steroid-secreting portion. It lies beneath the capsule and constitutes nearly 90% of the gland by weight.

• The medulla is the catecholamine-secreting portion. It lies deep to the cortex and forms the center of the gland.

Blood Supply

The adrenal glands are supplied with blood by the:

superiormiddle

and inferior suprarenal arteries.

.Embryologically, the cortical cells originate from mesodermal mesenchyme, whereas the medulla originates from neural crest cells that migrate into the developing gland.

Although embryologically distinct, the two portions of the adrenal gland are functionally related.

Cells of the Adrenal Medulla

The central portion of the adrenal gland, the medulla, is composed of a parenchyma of large, pale-staining epithelioid cells called chromaffin cells (medullary cells),connective tissue, numerous sinusoidal blood capillaries, and nerves.

Ganglion cells are also present in the medulla.

???

Can chromaffin cells be found outside of the adrenal medulla???

pheochromocytoma

• A rare tumor derived from chromaffin cells• produces excessive amounts of catechol

amines.• Most pheochromocytomas contain

predominantly chromaffin cells that secrete norepinephrine in comparison with the normal adrenal medulla that comprises about 85% epinephrine-secreting cells.

Zonation of the Adrenal Cortex

The adrenal cortex is divided into three zones on the basis of the arrangement of its cells:

• Zona glomerulosa, the narrow outer zone that constitutes up to 15% of the cortical volume

• Zona fasciculata, the thick middle zone that constitutes nearly 80% of the cortical volume

• Zona reticularis, the inner zone that constitutes only 5% to 7% of the cortical volume but is thicker than the glomerulosa because of its more central location