The structure of the outer and the inner regions of the supra-renal glands highly differ from each other, and each one produces different hormones. The outer supra-renal cortex is a glandular tissue, while the inner medulla is part of the sympathetic nervous system, and contains bundles of nerve fibres.
Three groups of hormones are produced by the supra-renal cortex:
- Mineral corticoids
An important mineralocorticosteroid is aldosterone, which regulates the sodium-potassium balance in the body and helps adjust blood pressure and volume. The main glucocorticosteroid is cortisol, which controls the body’s use of fat, protein, carbohydrates, and minerals. Besides this, it is quite helpful in resisting stress from exercise, infection, extreme temperatures, and bleeding. The androgens produced by the supra-renals are relatively weak in their effects, compared to those produced by the ovaries and testes during late puberty and adulthood. However, they play a very crucial role in the growth of hair near underarms and pubic areas, in both – males and females. In adult women, they are responsible for the sex drive. The supra-renal medulla produces epinephrine and norepinephrine. In stressful situations, when the sympathetic nervous system becomes activated, the hypothalamus stimulates the supra-renal medulla for the secretion of these hormones, which may later on facilitate or increase the stress response.
Anatomy of the gland
Going by the anatomical structure of the supra-renal gland, each gland sits on a fatty pad on top of the kidney. The cortex forms the bulk of the gland. The medulla contains nerve fibres and blood vessels.