24 Questions
What is the percentage of the cortical volume of the zona glomerulosa?
15%
What is the shape of the cells in the zona glomerulosa?
Columnar
What type of endoplasmic reticulum is abundant in the zona glomerulosa?
Smooth-surfaced endoplasmic reticulum
What is the main function of aldosterone?
Regulation of sodium and potassium homeostasis
Where do the cells of the zona glomerulosa secrete aldosterone?
All of the above
What is the function of aldosterone in the distal tubules of the nephron in the kidney?
Stimulate resorption of sodium
What is the arrangement of the cells in the zona glomerulosa?
Arranged in closely packed ovoid clusters and curved columns
What is the location of the zona glomerulosa in the adrenal gland?
Outer zone
What type of neurons innervate medullary chromaffin cells?
Cholinergic
What happens when chromaffin cells are grown in culture?
They extend axon-like processes
What inhibits axonal growth in chromaffin cells?
Glucocorticoid hormones
What is the primary function of epinephrine and norepinephrine?
To facilitate defensive reactions to stress
What is the function of ganglion cells in the medulla?
To modulate secretory activity of the adrenal cortex
What is the function of insulin?
To absorb glucose
What is the function of glucagon?
To release glucose
Where do ganglion cells extend their axons?
To the adrenal cortex and splanchnic nerves
What is the characteristic of the cells in the zona fasciculata?
They are densely filled with cytoplasmic lipid droplets
What is the primary function of glucocorticoids secreted by the zona fasciculata?
Regulation of gluconeogenesis and glycogenesis
What is the characteristic of the cells in the zona reticularis?
They are arranged in a network of irregular cords
What is the primary function of the adrenal medulla?
Secretion of catecholamines
What is the characteristic of chromaffin cells in the adrenal medulla?
All of the above
What is stored in the electron-dense granules of chromaffin cells?
Catecholamines
What is the feedback control mechanism of the zona reticularis?
CRH-ACTH system
What is the characteristic of the cells in the zona fasciculata after tissue preparation?
They appear vacuolated or spongy
Study Notes
The Adrenal Glands
- Located near the superior pole of the kidney, each adrenal gland consists of two parts: cortex and medulla.
Structure of Adrenal Gland
- Divided into three zones: zona glomerulosa, zona fasciculata, and zona reticularis.
Adrenal Cortex
- Zona glomerulosa:
- Narrow outer zone, 15% of cortical volume
- Cells arranged in ovoid clusters and curved columns
- Secrete mineralocorticoids, regulating sodium and potassium homeostasis and water balance
- Principal secretion: aldosterone
- Zona fasciculata:
- Thick middle zone, 80% of cortical volume
- Cells arranged in long cords, densely filled with cytoplasmic lipid droplets
- Secrete glucocorticoids, regulating gluconeogenesis and glycogenesis
- Cortisol acts on multiple cells and tissues to increase metabolic availability of glucose and fatty acids
- Zona reticularis:
- Inner zone, 5-7% of cortical volume
- Smaller cells in a network of irregular cords with wide capillaries
- Regulated by the feedback control of the CRH-ACTH system
Adrenal Medulla
- Composed of large, pale-staining polyhedral cells in cords or clumps, supported by a reticular fiber network
- Chromaffin cells, modified sympathetic postganglionic neurons, lacking axons and dendrites, specialized as secretory cells
- Contain electron-dense granules for hormone storage and secretion, containing catecholamines (epinephrine/adrenalin or norepinephrine/noradrenaline)
- Innervated by cholinergic endings of preganglionic sympathetic neurons, triggering hormone release by exocytosis
- Secretion of epinephrine and norepinephrine stimulates vasoconstriction, increased blood pressure, changes in heart rate, and metabolic effects during intense emotional reactions (fight-or-flight response)
Pancreas
- Beta cells of Langerhans islets secrete insulin, helping body cells absorb glucose
- Alpha cells secrete glucagon, releasing glucose
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