Adrenal Gland Anatomy and Physiology Flashcards
What are cortioids derived from?
Steroids
Derived from enzymatic modification of cholesterol
Where are steroid enzymes location intracellularly?
Mitochondria and sER
Are steroids permeable or impermeable?
Freely-permeable to membranes
Can steroid enzymes be stored? Where
No. They are synthesised and immediately released
Are steroids water soluble?
No
What time of day is plasma concentration of steroid hormones highest?
Higher in the morning than at night (diurnal rhythm)
How is cortisol circulated?
95% is bound to proteins
- mainly cortisol-binding globulin
Where do the adrenal glands lie?
Between the superiomedial aspects of the kidneys and the diaphragmatic crura
Surrounded by connective tissue and perinephric fat
What are the adrenal glands?
Endocrine glands
What size and weight are the adrenal glands?
4-6cm
6-8geach
How many arteries supply the adrenal glands and where do they branch of?
3
- Superior suprarenal artery - from subphrenic artery
- Middle suprarenal artery - from abdominal aorta near the SMA
- Inferior suprarenal artery - from the renal artery
Describe adrenal venous drainage
Medullary vein emerges from the hilum of each gland forming the suprarenal vein which goings:
IVC on the R
RV on the L
Describe the nerve supply to the adrenal glands
- Colic plexus
- Thoracic splenchnic nerves
Act on the chromaffin cells in the adrenal medulla
- secrete (nor)adrenaline
Describe the histological layout of the adrenal glands
Fibrous capsule
______
Outer Cortex
- Zona glomerulosa
- regulated by Ang II and K+
- secretes mineralocorticoids (aldosterone) and glucocorticoids (cortisol)
__ - Zona fasiculata
- regulated by ACTH
- secretes mineralocorticoids (aldosterone) and glucocorticoids (cortisol)
__ - Zona reticularis
- regulated by ACTH
- secretes: androgens, DHEA, and DHEAs
\_\_\_\_\_ Inner medulla - Chromaffin cells - regulated by nerves: colic plexus and thoracic splanhnic nerves - secretes: nor(adrenaline)
List the adrenal androgens and where are they secreted from?
DHEA Androstenedione DHEA DHEAs Testosterone
- zone reticularis
What areas secreted cortisol and aldosterone?
Zona glomerulosa and zona fasciculata
Sources of cholesterol?
Diet into circulation
De novo via acetyl CoA
What is the rate limiting step of cholesterol synthesis?
HMG-CoA Reductase enzyme
What is the first enzymatic step of steroid hormone synthesis?
Cholesterol –> pregnenolone
Via mitochondria P450 enzyme
What is the rate-limiting step of steroid hormone synthesis?
Transport of free cholesterol from cytoplasm to mitochondria by Steriodogenic Acute Regulatory Protein (StAR)
Where does steroid synthesis take place?
Mitochondria
What causes congenital adrenal hyperplasia?
21-hydroxylase deficiency
or
11-hydroxylase deficiency
Where are steroid receptors found?
Nucleus
How do steroid hormones act?
On nuclear receptors
Initiate transcription factors