PHY3181 Lecture Notes - Lecture 5: Aromatase, Acrosome, Smooth Muscle Tissue
30 Jun 2018
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THEME 1: MALE REPRO
Lecture 2: Male reproduction 1
FSH and LH are controlled separately –
different secondary messaging pathways (they
have different responses to GnRH). Frequency
of GnRH pulses codes for different rates of LH
and FSH secretion from pituitary
gonadotropes. Note that testicular steroids
reduce frequency of GnRH pulses.
Effect of castration on FSH and LH – evidence
for negative feedback on pituitary function.
Following castration, FSH and LH rise to
significantly high levels in the blood – this tells
us that there was something in the testis that
was moderating how much LH and FSH needed
to be made. Conclusions: That testosterone is
an important negative feedback hormone in
males via actions at the hypothalamus (GnRH).
Castration also removes the Sertoli cells –
source of negative feedback hormone inhibin
resulting in increased FSH
When hormonal control fails: hypogonadism
Normal
Primary
Secondary
Hypothal
GnRH
release
GnRH
release
Failure
Pituitary
Normal
LH and
FSH
Too
much LH
and FSH
Too little
LH and
FSH
Gonads
Normal
Small
testis
Small
testis
Gonadotropins
Normal
Hyper
Hypo
Too much or too little gonadotropins (LH and
FSH) is a bad thing. Small testis = small rates of
spermatogenesis infertility.
Hypogonadism: decreased testicular function,
as compared to what is expected for age,
involving impaired hormone secretion by
Leydig cells (androgens) and or Sertoli cells
(AMH, inhibin B) and/ or a disorder of
spermatogenesis
Primary (hypergonadotropic) hypogonadism:
testicular disorder eg leydig cell hypoplasia
(can occur from EDS – ethane dimethane
sulphonate).
Central (hypogonadotropic) hypogonadism:
disorder of the hypothalamus. Pituitary.
Male anatomy of the repro system
Note that during development the testis have
to come out of the abdomen and into the
scrotum. There is scrotal control of testicular
temperature. The gubernaculum is the
ligament that holds the testis down in the
scrotum. Through the pampiniform plexus, a
specialised spermatic blood supply counter
current exchange occurs. Blood coming from
the body down the testicular artery as it
descends – these arteries cool the blood via
heat transfer to the vein returning up the body.
Note that high temperatures stop
spermatogenesis and increase cancer risk.
Following heat exposure: fluid production
decreases, inhibin content decreases.
Note that testicular descent does not occur in
all mammals – in some species the testis
remain abdominal or move into an inguinal
position.
Testicular structure
• Rich in blood supply
• The lobuli testis is groups of
seminiferous tubules running together
all of the lobules drain to the retes
testis
• Note that all of the sperm being made
in the seminiferous tubules will come
out through the retes testis
• The thick capsule is the tunica
albuginea
• The Sertoli cells are in the seminiferous
tubules
Document Summary
Fsh and lh are controlled separately different secondary messaging pathways (they have different responses to gnrh). Frequency of gnrh pulses codes for different rates of lh and pituitary gonadotropes. Note that testicular steroids reduce frequency of gnrh pulses. secretion from. Effect of castration on fsh and lh evidence for negative feedback on pituitary function. Following castration, fsh and lh rise to significantly high levels in the blood this tells us that there was something in the testis that was moderating how much lh and fsh needed to be made. Conclusions: that testosterone is an important negative feedback hormone in males via actions at the hypothalamus (gnrh). Castration also removes the sertoli cells source of negative feedback hormone inhibin. Too much or too little gonadotropins (lh and. Small testis = small rates of spermatogenesis infertility. Hypogonadism: decreased testicular function, as compared to what is expected for age, involving impaired hormone secretion by.
