Let’s now move to the parathyroid gland. It’s
a gland that doesn’t have a lot of significance
histologically. It’s a pretty sort of dull looking
organ, if you like, it's one of the less prettier
organs of the body that we all have the pleasure
of examining with a light microscope.
But it stores and secretes parathyroid hormone.
And the principal cell that does that is called
the principal cell or chief cell. If you look
at the section on the left, you see predominantly,
these cells are rather basophilic or bluish
in their stain in this particular stain or
dye used. If you look very carefully, you
often see little clusters of sort of cells
that take up a reddish stain. The reddish
stains are these oxyphil stain cells.
You can see them contrasted here against the more
basophilic stain chief cells that dominate
the parathyroid gland. No one seems to know
the function of these oxyphil cells. So I’ve
put a question mark against their name. There
are probably of limited significance when
we consider the endocrine function of the
parathyroid gland. I’d like to now describe
for you the adrenal gland, often called the
suprarenal gland because it sits on top of
the kidney, the renal gland. The adrenal gland,
again, is one of these endocrine glands like
the pituitary gland that comes from two
origins. It has a cortex that’s derived
from mesoderm. This cortex occupies at least
90% of the gland. And it has a medulla that
occupies about 10%, that is in the center of
the gland, surrounded by the cortex. And this
medulla is derived from neural crest cells.
So have a look at these glands labelled in
the center, in the section of the center, and
make sure you clearly see the cortex and
the medulla. One thing to notice is that the
medulla has a brownish sort of stain.
And the cortex has a more pinker stain. So, different
stains have been used here to help distinguish
those two components of the adrenal gland,
the adrenal medulla, and the adrenal cortex.
And again, like the pituitary, they probably should
be considered as separate glands even though
geographically, they live together. Well,
when you look at the cortex, you can clearly
see if you look very, very carefully that
you can separate the cortex of the adrenal
gland into three separate zones based on how
they appear, even from this low magnification.
And I’m going to describe each of those
three zones because they secrete different
classes of hormonal product.