at the anterior pituitary in a bit more detail. On the left
hand side are these very pretty cells, stained, either acidophils
And as we’ll see in a moment,
different cells types are within these two types of
stained cells, and they secrete different hormonal products.
Those orange-shaped structures you see or colored
structures you see in the section are actually blood vessels,
blood capillaries. It’s a pituitary gland,
both the anterior pituitary and
the posterior pituitary being an
endocrine gland rather, are extremely vascular
as you’d expect because those blood vessels
take away the secretory product.
When we look at the posterior pituitary, it’s a different
sort of arrangement. It’s a different sort of histological structure.
If you look down the bottom slide,
out pituicyte, and also the herring body.
If you look very carefully at the herring body,
you can see little tiny brown granules.
These represent vesicles containing
the secretory products
from these neurons whose cell bodies remember
are located in the paraventricular nucleus or the
supraoptic nucleus up in the hypothalamus. So these
herring bodies are actually the terminal ends of these axons,
and they swell up as they fill with
oxytocin and, or ADH.
And those secretory products are going to be
released into nearby blood vessels, neurosecretion.
And those blood vessels are
going to be fenestrated, and that’s the top of capillary
that can easily mop up the secretory products
from the interstitium and then carry it
to the target organs located somewhere else
in the body.
The pituicyte is a supporting cell.
These axons are not myelinated.
The pituicyte is not a Schwann cell or
an oligodendrocyte or a cell that’s involved in myelination
or supporting unmyelinated fibers. It’s like an astrocyte.
Because if you think about it, the nuclei
that contain the cell bodies of these exons you see
in this section through the posterior pituitary,
those cell bodies are protected
within the blood brain barrier. And when the
axons then project down through the infundibulum
into the posterior pituitary,
they then break through that blood brain barrier.
Well, the astrocyte type cells here,
the pituicytes, maintain in some form,
the integrity of that blood brain barrier.
Because what they do is they not only wrap around
and support the axons, but they also wrap around the
blood capillaries, the fenestrated blood capillaries.
And they then create
this barrier and protection. So as I said
couple of times, they’re just like an astrocyte
as you see in the central nervous system.
They have a similar role.