from puberty and beyond. And in the adult, they
continue to be important to maintain the process of spermatogenesis and
the maintainence of the accessory sex glands. This is just the summary
of the hormonal control of spermatogenesis,
and the control of both the production of
testosterone and also inhibin from the Sertoli cell.
And basically, there are negative feedbacks involved.
The Leydig cell produces testosterone under the influence or stimulation
of LH, and produces testosterone. That testosterone is maintained at a
fairly constant level in the blood and it’s
concentrated in the seminiferous tubules by
the Sertoli cells. If those concentrations
go above a certain level, then there’s a
negative feedback on LH in the pituitary to
slow down the process of testosterone production.
Similarly, inhibin, which concentrates that
testosterone in the seminiferous tubule, that
is feeding back also on LH, again, to monitor
and maintain a constant level of testosterone
being produced by the Leydig cell.
Remember the Sertoli cell also produces the androgen
binding protein under the stimulation of FSH.
And that concentration, again, can provide a
negative feedback, again, to make sure that
that concentration is maintained at normal
levels. So there’s a number of feedback
mechanisms going on to control steroidogenesis
and also the production of various substances
from the Sertoli cell, involving the pituitary
gland. And it’s important that you understand
those feedbacks and also the effect of each
hormone have on the parts or the cells of
the male reproductive system that I’ve just
described. So, in summary, the testis contains
a vast surface area of seminiferous epithelium.
And that epithelium produces the spermatozoa.
The spermatozoa at this stage, when they’re
released into the tubule lumen, are not
quite mature. They receive that maturity and motility
in the ductus epididymis. The Leydig cells
secrete the androgens of which testosterone
is the major product. And the Sertoli cells
are very, very important. They have a number
of functions, three of which I’ve summarized
there. They support the spermatocyte. They are
even phagocytes as well, I’ve mentioned that.
They secrete androgen binding protein to concentrate
testosterone in the seminiferous
epithelium, which is essential for spermatogenesis.
And they contribute to creating a very important
blood-testis barrier. So I hope you now understand
a lot about the histology of the testis, the
structure of the testis and all the cells within
it, and the importance of all the hormones
created by the Leydig cell and the Sertoli
cell, and the interaction of these cells with
the pituitary gland.
So thank you for listening to this lecture.