Endocrine system part III

Histology 2016-2017
Department of Anatomy &Histology: Dr.Rajaa Ali
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Endocrine system part III
• 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 (Fig.1):
? 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.
Parenchymal cells of the cortex and medulla are of different embryologic origin.
• 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 . The parenchymal cells of the adrenal cortex are controlled in part by the anterior lobe of the pituitary gland and function in regulating metabolism and maintaining normal electrolyte balance.




Blood Supply:
The adrenal glands are supplied with blood by the superior, middle, and inferior suprarenal arteries. These vessels branch before entering the capsule, to produce many small arteries that penetrate the capsule. The vessels form a system that consists of :
? capsular capillaries that supply the capsule.
? fenestrated cortical sinusoidal capillaries that supply the cortex and then drain into the fenestrated modularly capillary sinusoids.
? medullary arterioles that traverse the cortex, traveling within the trabeculae , and bring arterial blood to the medullary capillary sinusoids.
Lymphatic vessels are present in the capsule and the connective tissue around the larger blood vessels in the gland.