The Adrenal Gland Flashcards
Where are the adrenal glands located?
Superior pole of kidneys in retroperitoneal space
What does each adrenal gland weigh in an adult?
About 4g
What are the two seperate endocrine glands that makes up the adrenal gland?
Adrenal medulla
Adrenal cortex
What percentage of the adrenal gland is the adrenal medulla?
About 25%
What is the adrenal medulla?
Modified sympathetic ganglion derived from neural cresh tissue
What does the adrenal medulla secrete?
Catecholamines, mainly epinephrine, also norepinephrine and dopamine
What percentage of the adrenal gland is the adrenal cortex?
About 75%
What is the adrenal cortex?
True endocrine gland derived from mesoderm and secretes 3 classes of steroir hormones
What class of hormones does the adrenal cortex secrete?
Steroid
What are the 3 classes of steroid hormones that the adrenal cortex secretes?
Mineralocorticoids
Glucocorticoids
Sex steroids
What is an example of a mineralocorticoid?
Aldosterone (involved in regulation of Na and K)
What is an example of a glucocorticoid?
Cortisol (involved in maintaining plasma glucose)
What is an example of a sex steroid?
Testosterone
Is the adrenal cortex or medulla more superficial?
Adrenal cortex
What is each layer of the adrenal cortex?
Zona glomerulosa (secretes aldosterone)
Zona fasciculate (secretes glucocorticoids)
Zona reticularis (secretes sex hormones)
What does the zona glomerulosa secrete?
Aldosterone
What does the zona fasciculate secrete?
Glucocorticoids
What does the zona reticularis secrete?
Sex hormones
How is it possible for different hormones to be secreted in different layers of the adrenal cortex?
All steroid hormones are derived from cholesterol
But different enzymes found in different adrenal zones results in different end products
What is a synthetic pathway?
Route taken to build up a specific product
What enzyme is responsible for both the formations of aldosterone and cortisol?
21-hydroxylase
What does HPA stand for?
What do defects in 21-hydroxylase cause?
Congenital adrenal hyperplasia resulting in:
- deficiency of aldosterone and cortisol (so disruption of salt and glucose balance)
- androgen biosynthesis is unaffected so accumulating steroid percursors are channels into excess adrenal androgen production
What does cortisol provide long loop feedback on?
CRH
Cortisol provides long loop feedback on CRH as part of the hypothalamic-pituitary-adrenal pathway, what provides short-loop feedback?
ACTH
Explain the process of a deficit in 21-hydroxylase causing adrenal hyperplasia?
1) Lack of enzyme inhibits synthesis of cortisol
2) Removal of negative feedback on ACTH and CRH release
3) Increased ACTH secretion is responsible for enlargement of adrenal glands
4) Negative feedback of ACTH on CRH synthesis remains balanced
5) Babies become very ill within a few days of birth
What type of hormone is cortisol?
Glucocorticoid hormone (influences glucose metabolism)
What percentage of plasma cortisol is bound to carrier protein?
About 95%
What plasma protien does most cortisol bind to?
Cortisol binding globulin (CBG)