- Identify the functional anatomy and zones of the adrenal glands and the principal hormones secreted from each zone.
- Describe and contrast the regulation of synthesis and release of the adrenal steroid hormones (glucocorticoids, mineralocorticoids, and androgens) and the consequences of abnormalities in their biosynthetic pathways.
- Understand the cellular mechanism of action of adrenal cortical hormones and identify their major physiologic actions, particularly during injury and stress.
- Identify the major mineralocorticoids, their biologic actions, and their target organs or tissues.
- Describe the regulation of mineralocorticoid secretion and relate this to the regulation of sodium and potassium excretion.
- Identify the causes and consequences of oversecretion and undersecretion of glucocorticoids, mineralocorticoids, and adrenal androgens.
- Identify the chemical nature of catecholamines and their biosynthesis and metabolic fate.
- Describe the biologic consequences of sympatho-adrenal medulla activation and identify the target organs or tissues for catecholamine effects along with the receptor types that mediate their actions.
- Describe and integrate the interactions of adrenal medullary and cortical hormones in response to stress.
- Identify diseases caused by oversecretion of adrenal catecholamines.
The adrenal glands are important components of the endocrine system. They contribute significantly to maintaining homeostasis particularly through their role in the regulation of the body’s adaptive response to stress, in the maintenance of body water, sodium and potassium balance, and in the control of blood pressure. The main hormones produced by the human adrenal glands belong to 2 different families based on their structure; these are the steroid hormones including the glucocorticoids, mineralocorticoids and androgens; and the catecholamines norepinephrine and epinephrine. The adrenal gland, like the pituitary, has 2 different embryologic origins, which as we will discuss, influence the mechanisms that control hormone production by each of the 2 components.
The adrenal glands are located above the kidneys. They are small, averaging 3–5 cm in length, and weigh 1.5–2.5 g and as mentioned above, consist of 2 different components; the cortex and the medulla (Figure 6–1), each with a specific embryologic origin. The outer adrenal cortex is derived from mesodermal tissue and accounts for approximately 90% of the weight of the adrenals. The cortex synthesizes the adrenal steroid hormones called glucocorticoids, mineralocorticoids, and androgens (eg, cortisol, aldosterone, and dehydroepiandrosterone [DHEA]) in response to hypothalamic-pituitary-adrenal hormone stimulation (Figure 6–2). The inner medulla is derived from a subpopulation of neural crest cells and makes up the remaining 10% of the mass of the adrenals. The medulla synthesizes catecholamines (eg, epinephrine and norepinephrine) in response to direct sympathetic (sympatho-adrenal) stimulation.
Figure 6–1.Graphic Jump Location
Adrenal glands. The adrenal glands are composed of a cortex and a medulla, each derived from a different embryologic origin. The cortex is divided into 3 zones: reticularis, fasciculata, and glomerulosa. The cells that make up the 3 zones have distinct enzymatic capacities, leading to a relative specificity in the products of each of the adrenal cortex zones. The ...