Adrenal Gland Histology
12.3 هزار بار بازدید -
3 سال پیش
-
The adrenal glands, also known
The adrenal glands, also known as supra-renal glands, are found immediately superior to the kidneys.
The adrenal glands are covered by a capsule made of thick connective tissue
The adrenal glands are retroperitoneal structures and composed of two major regions: the outer adrenal cortex and the inner adrenal medulla.
The cortex is the large outer region of the adrenal gland.
The adrenal cortex has three concentric zones in which the
cords of epithelial steroid producing cells are arranged
somewhat differently and which synthesize different classes of
steroid hormones :
The zona glomerulosa, immediately inside the capsule and comprising about 15% of the cortex, consists of closely packed, rounded or arched cords of columnar or pyramidal cells with many capillaries. The steroids made by these cells are called mineralocorticoids because they affect uptake of
Sodium , Potassium, and water by cells of renal tubules. The principal product is aldosterone, the major regulator of salt balance, which acts to stimulate sodium reabsorption in the distal convoluted tubules.
Moving deeper into the adrenal gland, the zona fasciculata is the largest of the three zones and comprises about 65 to 80 percent of the cortex.
Instead of clusters of cells, unlike the ones we saw in the zona glomerulosa, the secretory cells in this layer are arranged in long cords or columns of cells, often just one to two cells thick that are aligned perpendicular to the surface of the adrenal gland.
These cells have a larger amount of lipid-filled cytoplasm that results in a lighter stain and a “foamy” appearance. In this image, we can see the sinusoidal blood vessels that
run parallel to the columns of cells.
These cells secrete glucocorticoids, especially cortisol, which affect carbohydrate metabolism by stimulating gluconeogenesis in many cells and glycogen synthesis in the liver. Cortisol also suppresses many immune functions and can induce fat mobilization and muscle proteolysis.
The innermost zona reticularis comprises about 10% of the cortex and consists of smaller cells in a network of irregular cords interspersed with wide capillaries. The cells are usually more heavily stained than those of the other zones because they contain fewer lipid droplets and more lipofuscin pigment. Cells of the zona reticularis also produce cortisol but primarily secrete the weak androgens.
Let’s move onto the adrenal medulla. The adrenal medulla is the central part of the adrenal gland, surrounded by the cortex. The medulla plays a very important role in homeostasis: it serves to
secrete adrenaline and noradrenaline. The main secreting cells of the adrenal medulla are called chromaffin cells, which are neuroendocrine cells that are modified sympathetic ganglia.
Medullary chromaffin cells are innervated by preganglionic sympathetic neurons, which trigger epinephrine and norepinephrine release during stress and intense emotional reactions. Epinephrine increases heart rate, dilates bronchioles, and dilates arteries of cardiac and skeletal muscle. Norepinephrine constricts vessels of the digestive system and skin, increasing blood flow to the heart, muscles, and brain. Both hormones stimulate glycogen breakdown, elevating blood glucose levels. Together these effects augment the capability for defensive reactions or escape of stressors, the fight or flight response.
The adrenal glands are covered by a capsule made of thick connective tissue
The adrenal glands are retroperitoneal structures and composed of two major regions: the outer adrenal cortex and the inner adrenal medulla.
The cortex is the large outer region of the adrenal gland.
The adrenal cortex has three concentric zones in which the
cords of epithelial steroid producing cells are arranged
somewhat differently and which synthesize different classes of
steroid hormones :
The zona glomerulosa, immediately inside the capsule and comprising about 15% of the cortex, consists of closely packed, rounded or arched cords of columnar or pyramidal cells with many capillaries. The steroids made by these cells are called mineralocorticoids because they affect uptake of
Sodium , Potassium, and water by cells of renal tubules. The principal product is aldosterone, the major regulator of salt balance, which acts to stimulate sodium reabsorption in the distal convoluted tubules.
Moving deeper into the adrenal gland, the zona fasciculata is the largest of the three zones and comprises about 65 to 80 percent of the cortex.
Instead of clusters of cells, unlike the ones we saw in the zona glomerulosa, the secretory cells in this layer are arranged in long cords or columns of cells, often just one to two cells thick that are aligned perpendicular to the surface of the adrenal gland.
These cells have a larger amount of lipid-filled cytoplasm that results in a lighter stain and a “foamy” appearance. In this image, we can see the sinusoidal blood vessels that
run parallel to the columns of cells.
These cells secrete glucocorticoids, especially cortisol, which affect carbohydrate metabolism by stimulating gluconeogenesis in many cells and glycogen synthesis in the liver. Cortisol also suppresses many immune functions and can induce fat mobilization and muscle proteolysis.
The innermost zona reticularis comprises about 10% of the cortex and consists of smaller cells in a network of irregular cords interspersed with wide capillaries. The cells are usually more heavily stained than those of the other zones because they contain fewer lipid droplets and more lipofuscin pigment. Cells of the zona reticularis also produce cortisol but primarily secrete the weak androgens.
Let’s move onto the adrenal medulla. The adrenal medulla is the central part of the adrenal gland, surrounded by the cortex. The medulla plays a very important role in homeostasis: it serves to
secrete adrenaline and noradrenaline. The main secreting cells of the adrenal medulla are called chromaffin cells, which are neuroendocrine cells that are modified sympathetic ganglia.
Medullary chromaffin cells are innervated by preganglionic sympathetic neurons, which trigger epinephrine and norepinephrine release during stress and intense emotional reactions. Epinephrine increases heart rate, dilates bronchioles, and dilates arteries of cardiac and skeletal muscle. Norepinephrine constricts vessels of the digestive system and skin, increasing blood flow to the heart, muscles, and brain. Both hormones stimulate glycogen breakdown, elevating blood glucose levels. Together these effects augment the capability for defensive reactions or escape of stressors, the fight or flight response.
3 سال پیش
در تاریخ 1399/12/12 منتشر شده
است.
12,351
بـار بازدید شده