In this slide, you can see
an illustration of the
duct system that takes the spermatozoa away
from the testis. And I’ve listed each of
these ducts on the right-hand side and numbered
them because I’m going to refer to these
numbers to describe the duct system. Firstly,
look at the testis. I’ve already described
the testis in another lecture. But the testis
has a capsule around it called the tunica
albuginea. And that capsule divides the testis
into a number of lobules. And these testicular
lobules contain one to four long coiled tubes
we call seminiferous tubule. And each of these
tubules can be up to 50 centimeters long.
So this is its enormous length of epithelium
that is part of spermatogenic epithelium. This
tube was aligned by seminiferous epithelium,
which is the epithelium giving rise to the
spermatogenic cells or containing the spermatogenic
cells. And the final product of this epithelium
is to release spermatozoa into the lumen of
these tubules which then move their way towards
the mediastinum of the testis. Before they
get into the mediastinum of the testis, they
pass into straight tubules. You can see them
illustrated in the diagram and labelled 1 here.
Those straight tubules then carry the spermatozoa
along with fluid, into the mediastinum of the
testis, into channels referred to as the rete
testis, shown here labelled 2. And then, the fluid
and the spermatozoa travel from the mediastinum
into the epididymis via the efferent ducts.
These efferent ducts are about 12 to 20 of
them, they link the testis to the epididymis,
the ductus epididymis. When you look at the
epididymis, which is labelled 4 here, it’s
a very long coiled tube. It can range from
four to about six meters in length. It’s
the site where sperm are going to go through
their final maturation phase and become motile.
It’s also the site that they’re stored.
Now, that epididymis has a head, a body, and
a tail. The head is the component, the coil
part of the epididymis right up next to the
testis, joining the testis via these efferent
ducts. The body is in the bulk of the epididymis
passing around the posterior aspect of the
testis. And then it starts to one coil at
the tail region and it’s continuous then
with the vas deferens labelled here, 5. I want
you to keep in your minds a memory of this
particular picture, because I’m going to
refer now to all the different parts of the
epididymis, the vas deferens and even all the
duct systems coming out of the testis.
And I’m going to describe their histological
features or characteristics and their importance.
Now on the right-hand side, you can see a
histological section. This is taken right
near where the seminiferous tubules become
continuous with the straight tubule, number
1 in the diagram. You can see the seminiferous
tubule, the seminiferous epithelium is minimal.
It’s not as thick as you see in other parts
of the testis. It doesn’t contain a vast
number of spermatogenic cells because the
epithelium is changing as it moves from the
seminiferous tubule to the straight tubule.
In the straight tubule, it’s becoming cuboidal
or even columnar, there're a variety of shapes of
the epithelial cells, but generally speaking,
they adopt the cuboidal type of appearance.
And then the epithelium is maintained as we
pass through the rete testis shown here on
the right-hand section, and it’s equivalent
to this section area on the diagram number
2. These are just huge channels or spaces
that collect all the fluid containing the
spermatozoa from the seminiferous tubules.
And they have a cuboidal, sometimes an even
squamous epithelium. There is a little bit
of a variety in these tubes. It’s particularly
not that important, nor are the straight tubules
in terms of defining their histology and their
epithelial characteristics. The important
point is that they are channels that are going
to carry the spermatozoa from the testis up
towards the epididymis. And then the efferent
tubules look rather strange. They’re labelled
3 on the diagram, and they’re shown here
in the histological section. Have a look at
the epithelium. It’s rather an uneven surface,
an undulating or corrugated type lumen due
to the difference in the types of epithelial
cells here. Some are cuboidal, some are columnar.
It looks as though some are even pseudostratified.
It doesn’t matter too much. We tend to just
term this particular tube a pseudostratified
epithelium because really when you look at
a number of sections through these tubes, the bulk
of the epithelia illustrates a pseudostratified
appearance. They have, on their surface, cilia.
You can see some ciliated cells in this image.
And those cilia help to move the fluid along
and carry therefore the spermatozoa into the
epididymis. In the center of the lumen, you can
see some red stained components that represent
spermatozoa being transported along these
ducts, the efferent ducts.