biosciences eowyofoa eowyofoa
TRANSCRIPT
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• https://www.youtube.com/watch?v=kkGeOWYOFoA
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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.
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I think it may be – We’ve only
just passed the tonsils.
Is it much further to the Fallopian
tube?
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Reproductive systemsand hormones
Professor Geoff Shaw
Department of [email protected]
• 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
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Copyright Notice
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nn
diploid- 2n haploid- 1n
individualgerm stem
cells
zygote
mito
sis
male
female
sperm
n
n
n
n
n
n
n
n
2n
2n
2n
2n
egg
meiosis
fertilization
one cell
Germ cell
development
All other cells of the body:
Somatic cells
The SexualLife Cycle
see KLES4 Fig 19.4
Fertilization
mitosis
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mouse testis stained to show tubules inside
What are the main functions of the testis?
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Testes• sperm production
– occurs in seminiferous tubules
– controlled by Sertoli cells– spermatogenesis
• hormone production– testosterone
• steroid• androgen
– made by Leydig cells between tubules
Testosterone
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Seminiferous tubule
peritubular myoid cells
Sertoli cell
primaryspermatocyte
spermatogonium
LUMEN
spermatid
secondaryspermatocyte
sperm
MITOSIS
ME
IOS
IS
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Sperm
KLES4 Fig 19.22a
MEIOSISOvaries• egg production
– oogenesis– occurs in follicle– controlled by
granulosa cells• hormone production
– oestradiol• steroid - oestrogen • made by granulosa cells in
follicle– Progesterone
• steroid - progestin• made by corpus luteum
after ovulation
progesteroneoestradiol
egg (oocyte)
ovulation
follicle CL
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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?)
CLCL
CL
uterus
oviduct
ovary
this section enlargedon previous slide
CLCL
CL
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Testis hormones - Testosterone• Testosterone
– acts via androgen receptor in cells– stimulates accessory sex organs (eg
prostate and seminal vesicles)– modulates male-type behaviour
Testosterone
oestradiol
dihydro-testosterone (DHT)
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Ovary hormones - oestradiol
• Oestradiol– acts via oestrogen receptors in cells– controls oviduct, uterus, cervix, vagina and
other sex organs– promotes oestrus behaviour (mating)
Oestradiol
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Ovary hormones - progesterone
• Progesterone– acts via progestin receptors in cells– controls oviduct, uterus, cervix, vagina and
other sex organs– modulates effects of oestradiol
Progesterone
Control of testis• hypothalamo-pituitary-gonadal axis• gonadotrophin releasing hormone
(GnRH) from hypothalamus stimulates release of LH and FSH (the gonadotrophins) from the pituitary
• LH stimulates Testosterone production by testis
• FSH stimulates spermatogenesis• testosterone inhibits GnRH
secretion (negative feedback)
LH FSH
GnRH
testosterone
- hypothalamus
pituitarybrain
other brain centres
accessory sex organs and secondary sex characters
relatively constant T homeostatic control
Control of ovary (follicle growth)• hypothalamo-pituitary-gonadal axis• gonadotrophin releasing hormone
(GnRH) from hypothalamus stimulates LH and FSH (the gonadotrophins) release from the pituitary
• FSH stimulates– follicle growth/oogenesis – oestradiol production
• oestradiol regulates GnRH (negative feedback)
LH FSH
GnRH
oestradiol
- hypothalamus
pituitarybrain
other brain centres
reproductive tract
growing follicles
Control of ovary (ovulation)• Large follicles HIGH oestradiol• HIGH E2 (+)ve feedback• Surge of LH causes ovulation
LH FSH
GnRH
oestradiol
+ hypothalamus
pituitarybrain
reproductive tract preparationoestrous behaviour
mature follicles/ovulation
Control of ovary (after ovulation)• ovulated follicle transforms to
corpus luteum (corpora lutea)• oestradiol production falls• porgesterone production increases• progesterone negative feedback
on FSH preventing follicle growth• after about 2 weeks (human) CL
regresses allowing increased FSH and follicle growth
LH FSH
GnRH
progesterone
- hypothalamus
pituitarybrain
other brain centres
Uterus (preparation for pregnancy)
corpora lutea
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menstrual cycle hormones
see KLES5:Fig 28.11
(ute
rin
e lin
ing
)
http://upload.wikimedia.org/wikipedia/commons/c/cd/MenstrualCycle2.png
switch to positive feedback
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Contraception
• Combined oral contraceptive pill– progestin plus oestrogen– suppresses GnRH
↓ FSH and LH– prevents follicle growth
and ovulation
LH FSH
GnRH
oestradiol
- hypothalamus
pituitarybrain
reproductive tract
Progestin/oestrogen
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A male contraceptive pill?
see KLES4 Box 19.2
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Tubal Ligation
Vasectomy
From: Life,Purves et al.,6th Ed
Ch.42AnimalReproduction
Methods of Contraception
Contraceptive effectiveness
Method Mechanism
% of women getting pregnant within 1 year
Typical use Perfect use
No method 85 85
Spermicides kill sperm 29 18
“rhythm method” abstinence near time of ovulation 35 15
condom (male) prevents sperm entering vagina 15 2
contraceptive pill prevent ovulation 8 0.3
implanon prevents ovulation 0.05 0.05
IUD prevents embryo implantation 0.2-0.8 0.2-0.6
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
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2nd Year
ZOOLOGY:Further Studies Physiological Aspects
Animal structure and functionAnimal structure and function
Comparative Animal Physiology
Comparative Animal Physiology
Concepts in Cell & Devel Biology
Concepts in Cell & Devel Biology
3rd Year
Research ProjectResearch ProjectDevelopmental
Biology
DevelopmentalBiology
ReproductionReproduction
Sex: Science and Society(University breadth)
Sex: Science and Society(University breadth)
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http://www.lectureroftheyear.com.au/
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Next Lectures…
Developmental Biology,Digestion, Feeding and
Nutrition
Dr Stephen Frankenberg
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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
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HYPOTHALAMUS
hypothalamus
pituitary
PITUITARY
hypothalamus
pituitary
GONADS