well welcome to another MedCram video we're going to talk about the adrenal
cortex today and the first thing we've got to learn about is the anatomy
general cortex is part of the adrenal gland which sits right on top of the
kidney and you know you've got two kidneys one on each side of your body
and right above the kidney is this little triangular shaped organ called
the adrenal gland and it's got two areas it's got a medulla which is in the
middle and it's got a cortex and that's what we're going to talk about today is
this cortex this outer portion of the adrenal gland so let's zoom in a little
bit on that and talk about it okay so the adrenal cortex is a big triangle if
you will and we're just going to sort of ignore the middle portion which is the
medulla the adrenal cortex is divided into three layers there's the outer
layer okay and then there's an inner layer and the part that gets left over
is the middle layer so there's three layers basically and those three layers
of course has a name and the first layer the or the outermost layer is known as
the zona glomerulosa
the middle layer is the zona gesticulate and the last layer is the zona
reticularis so from outer to inner it's G F R it's nice way to remember it zona
glomerulosa zona fasciculata zona reticularis we'll talk about each of
these three layers the other thing I want to that I want you to know is the
type of hormones which is what the adrenal cortex secretes what type of
hormones they secrete they secrete steroid hormones and that's important to
know that because there are some hormones that are proteins or peptides
so why is it important to know that this secretes steroid hormones you can take a
look at the structure of the type of hormone that it secretes they're all
derived from cholesterol and the reason why that's important is because these
hormones are a lipid soluble because there are steroid now because of that
they're able to go in through the cell into the cell's nucleus now why is that
important it's because these hormones affect transcription of proteins in the
nucleus and that causes proteins to be made that can then be exported now why
that why that's important is because normally when you have hormones that are
proteins those proteins that are secreted into the blood will hit a
receptor on the surface of the cell which will cause something to happen
almost immediately so proteins protein hormones cause changes that happen very
quickly whereas steroid hormones which is what we're going to talk about here
cause changes that will happen slowly more slowly maybe over days or even
longer because these hormones actually go into your cell's nucleus
they cause transcription of different proteins which takes a long time as you
recall you have to have transcription then it goes to the rough endoplasmic
reticulum Golgi apparatus and then gets exported so we'll talk a little bit more
about that so if you remember our three layers we'll just call them here the
zona glomerulosa
the zona reticularis and the zona
actually zona fasciculata and the zona reticularis now if you're actually to
look at this linearly take a slice of the adrenal cortex you would see that
the bulk of the general cortex is actually made up of the zona fasciculata
about 10% up here and the other 10% down here okay so the fascicular da makes it
the major portion so what are the major hormones that are coming out of this
the major hormone out of the zona glomerulus or sorry the zona glomerulosa
is aldosterone we'll talk about that the major hormone out of the zona
fasciculata is cortisol and the major hormone coming out of the zona
reticularis are androgens the biggest one is testosterone okay so aldosterone
is what's known as eye mineral corticoid and cortisol is what's known as a
glucocorticoid okay so there you have it so the zona
glomerulosa makes mineral corticoids specifically aldosterone the zona
fasciculata makes glucocorticoids mainly cortisol and the zona reticularis makes
androgens primarily testosterone the way I like to look at and this kind of
brings up a nice point here with problems with these and we'll talk a
little bit all G in a little bit but let me sort of talk about what these do so
what does aldosterone do aldosterone works primarily at the distal convoluted
tubules
so it's right there and what does it do there it causes reabsorption of sodium
and dumping of potassium and protons that's what it does what does
glucocorticoids do or a cortisol cortisol basically is a hormone that
signals to the body that we need to increase glucose without cortisol you
would be dead basically you need to have cortisol it just sort of makes the whole
body run smoothly one of the primary functions is to increase glucose in the
body and it can do that through gluconeogenesis or glyco general lysis
ok androgens what do androgens do basically it's the
male secondary characteristics it's also responsible for sex drive in women this
is in fact woman's only source of androgens is from the adrenal cortex so
knowing these things knowing these functions and remember these are
steroids so they're going to go into the cells
so how would aldosterone work aldosterone would be secreted from the
zona glomerulosa it would then go over to the distal convoluted tubule cells it
would go into their nuclei and tell the nuclei to make little sodium potassium
pumps that would then be exported to the surface again these are steroid hormones
so what's telling this this organ to do all of this well the major one
is what's stimulating the zona glomerulosa to make aldosterone it's
potassium high potassium so high potassium tells the zona glomerulosa to
make aldosterone and that's what happens what's
stimulating this a substance called ACTH ACTH is a peptide or a amino acid
protein hormone that is secreted from the pituitary okay it also there's also
a little fragment that is made as well that has as part of it and this become
important later something called melanocytes stimulating hormone we'll
talk about that in a little bit that's nothing really need to know too much
about at this point what stimulates this again
ACTH okay and there's a negative feedback inhibition so ACTH stimulates
the oculata and ACTH also stimulates the reticularis to make androgens and
cortisol if for some reason this is not doing its job you're going to get more
ACTH why is that because cortisol is going to back feed on AC th to reduce it
and androgens the same way on ACTH obviously if aldosterone is causing the
potassium levels to go too low it's going to also negatively feedback on it
okay so we'll talk a little bit more about that in a little bit okay so let's
just review again we've got the adrenal cortex okay it's made of three layers
and we know what they are from the outside and it's G F R we know it
stimulates the outer layer the thing that stimulates the outer layer is
potassium okay and what does the outer layer make it makes
aldosterone which works at the distal convoluted tubules of the nephron the
inner layer the fascicular de is stimulated by AC th and the outer end
sorry that middle layer that fascicular lotta is going to make cortisol and the
inner layer is also stimulated by ACTH and it makes testosterone okay now if
there's a problem let's let's say that we could have a problem here with the
adrenal gland let's say the adrenal glands not working what would it look
like say none of the layers are working since there's no aldosterone we can't
dump potassium so you would see that potassium by the way this is called
Addison's disease so in Addison's disease this is where you have no
adrenal glands working
you would see what you would see an increase in potassium because
aldosterone is not working what else does aldosterone do it causes
dumping of protons so you would have a metabolic acidosis okay because you're
going to not be able to dump that and you're also not going to be able to
reabsorb sodium so your sodium would be low what else would you see your
cortisol levels not going to be working so you're going to see decrease glucose
and especially in stressful situations where you need glucose to do flight and
fight you're not going to have it and then finally lack of testosterone which
really doesn't cause that much of a problem at least acutely so what are you
going to see in Addison's disease hyperkalemia metabolic acidosis
hyponatremia and hypoglycemia and you also see because of that low sodium
you're going to have low blood pressure that's the big problem let's go to the
other side what happens if you have too much of this going on well you could
have that from something called Cushing's now it's called Cushing's
syndrome if and sorry this Cushing's disease and there's Cushing's syndrome
what's the difference between the two well Cushing's syndrome would be from
any cause Cushing's disease would be if there is too much ACTH from the
pituitary so disease is if there's too much a cth syndrome would be just too
much steroids maybe you're getting exogenously like someone's giving a
cortisol or prednisone so what are you get to see there based on this you're
getting a lot of aldosterone so you could see a low potassium you could see
a low proton that would be a metabolic alkalosis and you would also see an
increased sodium which would mean increase in your blood pressure what
about a cortisol you have a lot of cortisol so you'd also get high
or glycaemia as well and you also get a lot of testosterone so you get secondary
male sexual characteristics as well okay so this is the highs and the lows of it
if also because of that if you had a lot of this stuff function and guess what
your ACTH would be it should be low if you're not dealing with a Cushing's
disease if you're dealing with the Cushing's syndrome but if in fact the
pituitary is over secreting ACTH then that would cause everything to be
working over time and that would give you these syndromes that I was talking
about before alright so join me for part two of our
med cram lecture on the adrenal cortex