Adrenal gland

Summary

In this comprehensive overview of the adrenal glands, Dr. Morton delves into the anatomy, function, and hormone secretion of the adrenal cortex and medulla. He explains the topography, vascular supply, and histology of the adrenal glands, emphasizing their role in secreting key hormones such as aldosterone, cortisol, and epinephrine. Through detailed descriptions, he outlines the physiological mechanisms behind hormone production and regulation, including the renin-angiotensin-aldosterone system and the stress response. The lecture also covers conditions like Cushing's syndrome and the circadian rhythm of cortisol, offering a thorough understanding of these essential organs.

Takeaways

• 😀 The adrenal glands are located on top of the kidneys, also known as 'suprarenal glands'.
• 😀 The adrenal glands are retroperitoneal, meaning they are located behind the peritoneum, a membrane lining the abdominal cavity.
• 😀 The adrenal glands consist of two main parts: the cortex (outer) and medulla (inner), each with distinct functions.
• 😀 The adrenal cortex is responsible for secreting three types of hormones: aldosterone (mineralocorticoid), cortisol (glucocorticoid), and androgens.
• 😀 The adrenal medulla primarily secretes epinephrine (adrenaline), which is crucial for the body's fight-or-flight response.
• 😀 The adrenal glands receive blood supply from three arteries: the inferior phrenic artery, middle suprarenal artery, and inferior suprarenal artery.
• 😀 The right and left adrenal glands have different venous drainage systems. The right adrenal gland drains directly into the IVC, while the left drains into the renal vein.
• 😀 Aldosterone, secreted by the zona glomerulosa, regulates sodium and water retention, impacting blood pressure and volume.
• 😀 Cortisol, secreted by the zona fasciculata, plays a key role in the stress response and regulates sugar metabolism and inflammation.
• 😀 The circadian rhythm influences cortisol levels, with peak levels occurring in the morning and decreasing throughout the day.
• 😀 Hypersecretion of cortisol, as seen in Cushing's syndrome, can lead to symptoms like weight gain, insulin resistance, and suppressed immune function.

Q & A

What is the adrenal gland, and where is it located?

The adrenal gland is located on top of the kidneys, with one adrenal gland on each kidney. It is also known as the suprarenal gland due to its position above the kidneys.

What does 'retroperitoneal' mean in relation to the adrenal glands?

Retroperitoneal means that the adrenal glands are located behind the peritoneum, the lining of the abdominal cavity. This term also applies to other organs like the kidneys and ureters.

What are the main regions of the adrenal cortex?

The adrenal cortex consists of three main regions: the zona glomerulosa, zona fasciculata, and zona reticularis. Each region secretes different hormones.

How is the adrenal gland vascularized?

The adrenal gland receives blood supply from three arteries: the inferior phrenic artery, the middle suprarenal artery, and the inferior suprarenal artery. The gland is drained by the suprarenal veins.

What hormones are secreted by the adrenal cortex?

The adrenal cortex secretes aldosterone (from the zona glomerulosa), cortisol (from the zona fasciculata), and androgens (from the zona reticularis).

What is the function of aldosterone, and how is it regulated?

Aldosterone, secreted by the zona glomerulosa, regulates sodium and water balance, increasing blood volume and pressure. It is stimulated by renin-angiotensin system activation, increased potassium levels, and ACTH.

What is the role of cortisol, and how is its secretion regulated?

Cortisol, a glucocorticoid produced by the zona fasciculata, helps regulate blood sugar and is involved in the stress response. Its secretion is regulated by CRH and ACTH from the hypothalamus and pituitary gland.

What is the circadian rhythm of cortisol secretion?

Cortisol levels follow a circadian rhythm, peaking in the early morning and gradually decreasing throughout the day, with the highest levels typically between 8:00-9:00 AM.

What is the impact of excessive cortisol secretion?

Excessive cortisol secretion can lead to Cushing's syndrome, characterized by symptoms like weight gain, high blood pressure, insulin resistance, slow wound healing, and increased fracture risk due to decreased bone formation.

What hormones are secreted by the adrenal medulla, and what is their function?

The adrenal medulla secretes catecholamines, primarily epinephrine (adrenaline), which increase heart rate, blood pressure, and trigger the fight-or-flight response. It is stimulated by sympathetic nervous system activation.