- The adrenal cortex is of mesodermal origin
- 70-90% of adrenal gland by volume
- Responsible for the production of:
- Steroid hormones: cortisol, aldosterone
- Androgens
The Adrenal Glands
The Adrenal Glands
The curriculum asks for knowledge of the 'functional anatomy of the adrenal gland' and more specifically the 'adrenal medulla'.
- The adrenal glands are small, triangular, 2.5g supra-renal glands associated with the superior pole of each kidney at the level of T12
- They comprise of a capsule, an outer cortex, and an inner medulla
- Originates from the neural crest (neuroectoderm)
- 10-30% of adrenal gland by volume
- The medulla comprises of chromaffin cells
- It functions as a specialised autonomic ganglion (/post-ganglionic neurone) that secretes catecholamines in response to sympathetic stimulation
- It is innervated by T5-T9 pre-ganglionic sympathetic fibres secreting acetylcholine
| Hormones secreted by the adrenal medulla |
| Adrenaline (80%) |
| Noradrenaline (20%) |
| Dopamine |
| Adrenomedullin |
| Chromogranin A |
| Metenkephalin |
| ATP |
- Medullary catecholamine secretion is significant, forming the majority of sympathetic tone
- Equivalent resting secretion rates are:
- Adrenaline 0.2μg/kg/min
- Noradrenaline 0.05μg/kg/min
- Most (90%) of the adrenaline synthesised within the medulla is subject to enzymatic (COMT/MAO) degradation and recycling
- Normal half-life of catecholamine stores is 8-12hrs