Anatomy and Physiology: Adrenal Glands Review

Adrenal Cortex and Hormones

• Cortisol is primarily secreted by the zona fasciculata, the middle layer of the adrenal cortex.
• The major stress hormone released during stress is cortisol, which plays a crucial role in the body's response to stress.
• Cortisol increases blood glucose levels by promoting gluconeogenesis and reducing glucose utilization in peripheral tissues.

Effects of Cortisol

• Sustained cortisol levels can lead to abnormal fat distribution, often resulting in central obesity or "moon facies."
• Excessive secretion of cortisol from the adrenal cortex causes Cushing's syndrome, characterized by various metabolic changes.

Hormonal Functions

• Weak androgens, such as DHEA (dehydroepiandrosterone), are produced in the zona reticularis, the innermost layer of the adrenal cortex.
• Epinephrine, secreted by the adrenal medulla, is approximately ten times more potent than norepinephrine and is crucial for the fight-or-flight response.

Effects on Female Physiology

• Excessive secretion of androgens can lead to increased virilization or hirsutism in females, causing male-patterned hair growth.
• A neuroendocrine tumor secreting excessive catecholamines is known as a pheochromocytoma.

Cushing's Disease Manifestations

• Cushing's disease manifests through symptoms like hypertension, obesity, skin changes (bruising, thinning), and mood swings, resulting from excessive cortisol.

Cortisol Impact on Protein and Immune Function

• Cortisol inhibits protein synthesis, promoting muscle breakdown rather than growth, which can contribute to muscle wasting.
• Cortisol has a key immunosuppressive role, shifting the immune response towards a T helper 2 phenotype, reducing inflammation.

Adrenal Gland Organization

• The zona glomerulosa, the outer layer of the adrenal cortex, produces aldosterone, the primary mineralocorticoid.
• The zona intermedia facilitates the excretion of hydrogen ions, playing a role in acid-base balance.

Renin-Angiotensin-Aldosterone Pathway

• Aldosterone’s primary function in the renin-angiotensin-aldosterone system is to increase sodium reabsorption and potassium excretion, thereby regulating blood pressure.

Adrenal Medulla

• The adrenal medulla, comprising 10-20% of the adrenal glands, is part of the sympathetic nervous system, secreting catecholamines (epinephrine and norepinephrine).

Aldosteronism

• Excessive excretion of aldosterone, known as aldosteronism, is usually related to conditions like adrenal adenomas or hyperplasia, leading to hypertension and electrolyte imbalances.

Review the anatomy and hormones of the adrenal glands, including the structure of the retroperitoneal glands and the functions of the adrenal cortex. Understand the key components of the body’s response to stress.