Corticosteroid production and regulation Flashcards
What are steroids derived from?
Steroid hormones are derived from enzymatic modification of cholesterol
how is steroidogenesis regulated?
by controlling the enzymes which convert cholesterol into the steroid hormone
where are Enzymes which produce steroid hormones from cholesterol located?
in mitochondria and smooth ER
are steroid hormones stored after synthesis?
No, they are not stored but synthesized and immediately released
As steroid hormones aren’t water soluble, how are they carried in blood?
they are carried in the blood complexed to specific binding globulins.
what binding globulin carries cortisol?
Corticosteroid binding globulin
where are adrenal glands located?
in abdomen above kidneys
describe the size and colour of adrenal glands
Endocrine glands are 4-6cm
Yellow in colour due to high cholesterol
what are adrenal glands composed of?
Composed of outer cortex and inner medulla
how are the cortex and medulla adrenal glands different ?
Medulla is embryologically and histologically distinct to cortex, they are two different glands
Medulla- rich in blood + nerve supply
Cortex- consists of different zones
what is the arterial supply of adrenal cortex?
superior, middle and inferior suprarenal arteries
How does arterial blood flow and what vessel does it become?
moves towards the centre of the gland and flows into the medullary vein
describe the venous blood flow of the adrenal cortex?
Medullary vein emerges from the hilum before forming the suprarenal veins, which join the inferior vena cava on the right side and the left renal vein on the left
what is the adrenal nerve supply derived from? what do the nerves supply?
derived from the coeliac plexus and the thoracic splanchnic nerves.
The nerves supply the chromaffin cells of the adrenal medulla.
what surrounds the adrenal cortex?
Fibrous capsule
Name the 3 layers of the adrenal cortex
Zona Glomerulosa
Zona Fasciculata
Zona Reticularis
SALT, SUGAR, SEX
describe the cell type in ZG, what hormone it secretes, what it is regulated by and what process it regulates
Cluster of small cells
Regulated by RAS and K+
Produces mineralocorticoids e.g. aldosterone, deoxycorticosterone.
Regulates Na+ homeostasis
Cluster of small cells with ball-like structure
describe the cell type in ZF, what hormone it secretes, what it is regulated by and what process it regulates
Column like cells
Regulated by ACTH
Produces Glucocorticoids e.g. cortisol, corticosterone
Regulates carbohydrate metabolism
describe the cell type in ZR, what hormone it secretes, what it is regulated by and what its role is
Haphazard cell arrangement
Regulated by ACTH
produces adrenal androgens e.g. DHEA, DHEA-sulphate
Sole source of androgens – (important in women as males has testes which make testosterone)
what is found in the medulla?
Chromaffin cells
And Numerous capillaries and veins – produces catecholamines like adrenaline
what is the Rate-limiting enzyme is cholesterol synthesis?
HMG-CoA reductase
in what form is cholesterol taken up by a cell?
in the form of low density lipoprotein (LDL).
what happens after LDL is taken into cells?
It is broken down into esterified cholesterol, and then free cholesterol – ready for steroid biosynthesis
What is the first enzymatic step in steroid synthesis? what enzyme catalyses this reaction? where is it found?
the conversion of cholesterol to pregnenolone
Cytochrome P450 enzyme , found in inner mitochondrial membrane
