• https://www.youtube.com/watch?v=kkG
eOWYOFoA
BioSciences
Q. If it takes only one sperm to fertilise an egg, why do
we need millions of sperm in an ejaculate ?
A. The sperm won’t stop to ask for directions.
BioSciences
Is it much further
to the Fallopian
tube?
I think it may be
– We’ve only
just passed the
tonsils.
BioSciences
Reproductive systems
and hormones
Professor Geoff Shaw
Department of Zoology
g.shaw@zoology.unimelb.edu.au
• KLES5: Chapter 20;
Chapter 28 esp gonads and HPG axis
section pp 693-695, fig 28.11
• KLES4: Chapter 19;
Chap 27, esp p 647-648, Fig 27.10
BioSciences
Copyright Notice
BioSciences
The
Sexual
Life
Cycle
Fertilization
diploid- 2n
one
cell
zygote
haploid- 1n
2n
n
n
fertilization
All other cells
of the body:
Somatic cells
2n
Germ
cell
development
individual
germ stem
cells
2n
male
2n
sperm
n
n
n
n
n
n
female
egg
n
n
meiosis
BioSciences
see KLES4 Fig 19.4
mouse testis stained to show
tubules inside
BioSciences
What are the main functions of the testis?
Testes
• sperm production
– occurs in seminiferous
tubules
– controlled by Sertoli cells
– spermatogenesis
• hormone production
– testosterone
• steroid
• androgen
– made by Leydig cells
between tubules
Testosterone
BioSciences
Seminiferous tubule
LUMEN
sperm
spermatid
secondary
spermatocyte
primary
spermatocyte
Sertoli cell
spermatogonium
peritubular
myoid cells
BioSciences
Sperm
BioSciences
KLES4 Fig 19.22a
Ovaries
egg (oocyte)
• egg production
– oogenesis
– occurs in follicle
– controlled by
granulosa cells
• hormone production
– oestradiol
• steroid - oestrogen
• made by granulosa cells in
follicle
follicle
CL
– Progesterone
• steroid - progestin
• made by corpus luteum
after ovulation
oestradiol
progesterone
CL
Mouse female reproductive
tract:
microscope slide
• note the thick secretory lining
of the uterus (endometrium),
regulated by oestradiol and
progesterone
• multiple corpora lutea (CL) in
this species (why?)
BioSciences
CL
CL
uterus
ovary CL
oviduct
CL
CL
this section enlarged
on previous slide
Testis hormones - Testosterone
• Testosterone
– acts via androgen receptor in cells
– stimulates accessory sex organs (eg
prostate and seminal vesicles)
– modulates male-type behaviour
oestradiol
Testosterone
dihydro-testosterone (DHT)
BioSciences
Ovary hormones - oestradiol
• Oestradiol
– acts via oestrogen receptors in cells
– controls oviduct, uterus, cervix, vagina and
other sex organs
– promotes oestrus behaviour (mating)
Oestradiol
BioSciences
Ovary hormones - progesterone
• Progesterone
– acts via progestin receptors in cells
– controls oviduct, uterus, cervix, vagina and
other sex organs
– modulates effects of oestradiol
Progesterone
BioSciences
Control of testis
other brain centres
• hypothalamo-pituitary-gonadal axis
• gonadotrophin releasing hormone
hypothalamus
(GnRH) from hypothalamus
brain
GnRH
stimulates release of LH and FSH
pituitary
(the gonadotrophins) from the
pituitary
LH
FSH
• LH stimulates Testosterone
testosterone
production by testis
• FSH stimulates spermatogenesis
• testosterone inhibits GnRH
accessory sex organs and
secretion (negative feedback)
secondary sex characters
relatively constant T  homeostatic control
Control of ovary (follicle growth)
other brain centres
• hypothalamo-pituitary-gonadal axis
• gonadotrophin releasing hormone
hypothalamus
(GnRH) from hypothalamus
brain
GnRH
stimulates LH and FSH (the
pituitary
gonadotrophins) release from the
pituitary
LH
FSH
• FSH stimulates
oestradiol
– follicle growth/oogenesis
growing follicles
– oestradiol production
• oestradiol regulates GnRH
reproductive tract
(negative feedback)
Control of ovary (ovulation)
• Large follicles  HIGH oestradiol
• HIGH E2  (+)ve feedback
• Surge of LH causes ovulation
+
hypothalamus
GnRH
LH
brain
pituitary
FSH
oestradiol
mature follicles/
ovulation
reproductive tract
preparation
oestrous behaviour
Control of ovary (after ovulation)
other brain centres
• ovulated follicle transforms to
corpus luteum (corpora lutea)
hypothalamus
• oestradiol production falls
brain
GnRH
• porgesterone production increases
pituitary
• progesterone  negative feedback
on FSH preventing follicle growth
LH
FSH
• after about 2 weeks (human) CL
progesterone
regresses allowing increased FSH
corpora lutea
and follicle growth
Uterus
(preparation for pregnancy)
menstrual cycle
hormones
(uterine lining)
switch to positive feedback
BioSciences see KLES5:Fig 28.11
http://upload.wikimedia.org/wikipedia/commons/c/cd/MenstrualCycle2.png
Contraception
• Combined oral
contraceptive pill
– progestin plus oestrogen
– suppresses GnRH
 ↓ FSH and LH
– prevents follicle growth
and ovulation
Progestin/
oestrogen
-
hypothalamus
GnRH
LH
brain
pituitary
FSH
oestradiol
reproductive tract
BioSciences
A male contraceptive pill?
BioSciences
see KLES4 Box 19.2
Methods of Contraception
Vasectomy
Tubal Ligation
From:
Life,
Purves et al.,
6th Ed
BioSciences
Ch.42
Animal
Reproduction
Contraceptive effectiveness
% of women getting
pregnant within 1 year
Typical use
Perfect use
85
85
29
18
“rhythm method” abstinence near time of ovulation
35
15
condom (male)
15
2
8
0.3
0.05
0.05
0.2-0.8
0.2-0.6
Method
Mechanism
No method
Spermicides
kill sperm
prevents sperm entering vagina
contraceptive pill prevent ovulation
implanon
prevents ovulation
IUD
prevents embryo implantation
vasectomy
prevents release of sperm
0.15
0-0.1
tubal ligation
prevents egg from entering uterus
0-0.5
0-0.5
http://www.contraceptivetechnology.org/table.html
ZOOLOGY:
Further Studies Physiological Aspects
2nd Year
Animal structure and function
Comparative Animal Physiology
3rd Year
Reproduction
Research Project
Concepts in Cell &
Devel Biology
Developmental Sex: Science
Biology
and Society
(University breadth)
BioSciences
http://www.lectureroftheyear.com.au/
BioSciences
Next Lectures…
Developmental Biology,
Digestion, Feeding and
Nutrition
Dr Stephen
Frankenberg
BioSciences
What do I expect you to learn from this lecture?
•
•
•
•
meiosis and the alternation of haloid and diploid generations
structure and functions of the testis – sperm and testosterone
stages of spermatogenesis and structure of mature sperm
structure and function of the ovary – eggs, follicles
(oestradiol), CL (progesterone)
• hypothalamo-pituitary control of testis and ovary
• hormonal control and the menstrual cycle
• contraceptives – mechanisms and efficiency
BioSciences
BioSciences
HYPOTHALAMUS
hypothalamus
pituitary
hypothalamus
pituitary
PITUITARY
GONADS