freebta.blogg.se

There are two adrenal glands, one at the top of each kidney. We can now learn how stress affects the various regions and zones of the adrenal glands. The previous article about adrenal stress and adaptation discussed the concepts of stress, homeostasis and allostasis. These vessels originate from two lymphatic plexuses – one deep to the capsule, and the other in the medulla.Structure and Hormones of the Adrenal Glands Lymph drainage is to the lumbar lymph nodes by adrenal lymphatic vessels.

Sympathetic innervation to the adrenal medulla is via myelinated pre-synaptic fibres, mainly from the T10 to L1 spinal cord segments. The adrenal glands are innervated by the coeliac plexus and greater splanchnic nerves. The right adrenal vein drains into the inferior vena cava, whereas the left adrenal vein drains into the left renal vein. Right and left adrenal veins drain the glands.

These hormones produce a ‘ flight-or-fight‘ response. It contains chromaffin cells, which secrete catecholamines (such as adrenaline) into the bloodstream in response to stress. The medulla lies in the centre of the gland, and is dark brown in colour. Fig 3 - Histological appearance of the cortex and medulla of the adrenal gland. Fig 2 - Posterior view of the abdomen, demonstrating the anatomical relations of the adrenal glands. It also secretes a small amount of corticosteroids. Zona reticularis – produces and secretes androgens such as dehydroepiandrosterone (DHES).It also secretes a small amount of androgens. Zona fasciculata – produces and secretes corticosteroids such as cortisol.Zona glomerulosa – produces and secretes mineralocorticoids such as aldosterone.Functionally, the cortex can be divided into three regions (superficial to deep): It secretes two cholesterol derived hormones – corticosteroids and androgens. The cortex and medulla synthesise different hormones. Medulla – derived from the ectodermal neural crest cells.Cortex – derived from the embryonic mesoderm.They are two separate endocrine glands, with different embryological origins: The outer cortex and inner medulla are the functional portions of the gland. The adrenal glands consist of an outer connective tissue capsule, a cortex and a medulla. Veins and lymphatics leave each gland via the hilum, but arteries and nerves enter the glands at numerous sites.