PHYS20008 Lecture Notes - Lecture 32: Oocyte, Spermatogonium, Gametogenesis
12 Jun 2018
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Lecture 32
PHYS20008 - HUMAN PHYSIOLOGY
LECTURE 32
REPRODUCTION 1: GAMETOGENESIS
TODAY
•Overview gametogenesis
•Male
•Hormonal influences
•Female
•Hormonal influences
REPRODUCTIVE
FUNCTIONS
•Male
•Spermatogenesis
•Hormone secretion
•Delivery of sperm to the
female
•Fall asleep
•Female
•Oogenesis
•Hormone secretion
•Reception of sperm
•Fertilization
•Gestation
•Parturition
•Lactation
•Male
•Quiescent till puberty
(mitosis stage)
•4 sperm per germ cell
•Female
•Development in embryo
(start of meiosis) born with
all her 1o oocytes
•1 egg per germ cell
•Spermatogenesis is the
formation of sperm. It begins in
puberty. Oogenesis is the
production of eggs? And begins
in fetal life.
•In males, during the embryonic phase, the spermatogonium are undergoing mitotic divisions.
Once they begin going through meiosis there is no going back; can’t produce more of itself
indefinitely. In males, it is important that we maintain mitotic cells rather than enter into meiosis
early as males need to produce sperm their entire lives.
•Upon puberty, they leave the quiescent phase and some begin to undergo meiotic divisions to
create sperm, and some that stay mitotic to create spermatogonium. The first stage of meiosis
(divisions) begins here.
•In females, from 1 primary oocyte we end up with 1 mature oocyte (gamete), 1 egg. We have 2
left over polar bodies which dissolve.
•Females are born with all of the eggs we will ever have.
Lecture 32
PHYS20008 - HUMAN PHYSIOLOGY
HYPOTHALAMUS
•Anterior
•ACTH
(adrenocorticotropin)
•FSH, LH
(reproduction)
•TSH (thyroid
stimulating hormone)
•GH (growth
hormone)
•Posterior
•Vasopressin (ADH)
and Oxytocin
•GnRH: Gonadotropin-
releasing hormone. Signals
anterior pituitary to release the
FSH and LH. This is the same
in males and females.
•Released from anterior pituitary
under hypothalamic control:
•FSH: Follicle-stimulating
hormone
•LH: Luteinizing hormone
•By regulating GnRH we can
regulate both FSH and LH.
•They can also be regulated
independently too.
•Hypothalamus is involved in
things that involve both
autonomic function and
behavioural responses; so no
surprise it is involved in
reproduction.
OVERVIEW OF MAJOR HORMONES
•Gonads
•Androgens (includes testosterone)
•Dominant in males
•Oestrogens
•Dominant in females
•Progesterone
•Females; ‘pro-gestation’.
•Important when pregnant because we don’t want to shed the uterine lining when pregnant.
•Inhibin
•Works as a negative feedback mechanism.
Lecture 32
PHYS20008 - HUMAN PHYSIOLOGY
SPERMATOGENESIS
(MALES)
•Sertoli cells
•Support and regulate
•ABP
•Androgen binding protein
•Inside the elongated tubules
there are different cells. Blue
= spermatogonia, in between
them there are sertoli cells
which nourish the
spermatogonia, and outside
the tubules we have leydig
cells, responsible for releasing
testosterone.
•Spermatogonia divide and
turn into sperm and then
hang out in vas deferens.
REGULATION OF
SPERMATOGENESIS
•Testosterone secretion is continuous from
puberty.
•GnRH → LH → Leydig cells → testosterone →
sex characteristics
•GnRH → FSH → Sertoli cells → spermatocyte
maturation.
•Negative feedback (Inhibin, testosterone)
•Lutenising hormone stimulates leydig cells to
release testosterone. Both lutenising and leydig
begin with an L and LL Cool J talked about this
stuff a lot.
•Release androgen binding protein, which binds
to testosterone, meaning the testosterone won’t
be able to leave the tubule. Can keep
testosterone here without losing it to the blood
stream.
•Blocking production of FSH reduces sperm
production without inhibiting testosterone..
•Granulosa cells and theca cells within
a developing follicle release enough
oestrogen and progesterone to
regulate the entire female ovarian and
uterine menstrual cycles
Document Summary
And begins in fetal life: in males, during the embryonic phase, the spermatogonium are undergoing mitotic divisions. Once they begin going through meiosis there is no going back; can"t produce more of itself indefinitely. The first stage of meiosis (divisions) begins here: in females, from 1 primary oocyte we end up with 1 mature oocyte (gamete), 1 egg. We have 2 left over polar bodies which dissolve: females are born with all of the eggs we will ever have. Hypothalamus: anterior, acth (adrenocorticotropin, fsh, lh (reproduction, tsh (thyroid stimulating hormone, gh (growth hormone, posterior, vasopressin (adh) and oxytocin, gnrh: gonadotropin- releasing hormone. Overview of major hormones: gonads, androgens (includes testosterone, dominant in males, oestrogens, dominant in females, progesterone, females; pro-gestation", important when pregnant because we don"t want to shed the uterine lining when pregnant, inhibin, works as a negative feedback mechanism. Spermatogenesis (males: sertoli cells, support and regulate, abp, androgen binding protein, inside the elongated tubules there are different cells.
