Adrenal glands are paired structures located on the top of the kidneys. Each adrenal gland has two parts: external adrenal cortex and internal adrenal medulla. Adrenal cortex shows three concentric zones: zone glomerulosa, zona fasciculata, and zona reticularis. Adrenal medulla consists of rounded groups of relatively large and granular cells called chromaffin cells.
Adrenal Cortex vs Adrenal MedullaAdrenal Cortex
1. It is outer firm part of the adrenal gland
2. It forms about 75% part of the gland.
3. It is enclosed by a fibrous capsule.
4. It develops from the mesoderm.
5. It comprises three regions or zones a) Outer thin zona glomerulosa b)middle thick zona fasciculata and c) inner thin zona reticularis.
6. It is essential for life. Its destruction causes death.
7. It is stimulated to release its hormones by ACTH (Addrenocorticotrophic hormone) from the anterior lobe of pituitary gland.
8. It secretes three groups of hormones: mineralocorticoids, glucocorticoids and gonadocorticoids.
9. There is no cooperation between adrenal cortex and sympathetic nervous system.
1. It is central soft part of the adrenal gland
2. It forms about 25% part of the gland.
3. It is not enclosed by a fibrous capsule.
4. It develops from ectoderm.
5. It is not differentiated into regions. It consists of chromaffin cells. The adrenal medulla is simply an extension of the sympathetic nervous system.
6. It is not so essential for life. Its destruction does not cause death.
7. It is stimulated to secrete its hormone by nerve impulses reaching through sympathetic nerve fibres.
8. It secretes two similar hormones: adrenaline and nonadrenaline.
9. Adrenal medulla and sympathetic nervous system function as an integral ststem called sympatheticoadrenal system.