1. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
A man took his pregnant wife to the hospital to give birth. The doctor told them that they'd developed a new machine and asked if the couple would like to try it out. The machine could take some of the pain of childbirth from the mother and give it to the father to ease the mother's burden.
Well, they thought that was a good idea, and decided to give it a try. The doctor initially set the machine on 10 percent, telling the man that even 10 percent was probably more pain than he'd ever experienced. But the husband was surprised at how little pain he was feeling, and asked the doctor to raise the level.
The doctor increased it to 20 percent, and when the man still felt fine, he raised it to 50 and finally 100 percent.
After it was all over, the man stood up, and stretched a little. Both he and his wife felt fine, and they shortly left the hospital to take the baby home.
It was then that they found the mailman dead on their doorstep

2. Masters in Zoology Information Session
When: Thursday 4th September pm
Where: Drummond room, ground floor Zoology
Find out about masters in Zoology and potential projects. Meet and talk to potential supervisors.
Department of ZOOLOGY

3. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
BIOL30001 Reproductive Physiology
Parturition
Geoff Shaw
References
EssRep7 Chapters 14-17
Austin & Short 2nd Edn Book 2 chap 4, The fetus and birth
Thorburn, Hollingworth & Hooper (1991) The trigger for parturition in the sheep: fetal hypothalamus or placenta. J Developmental Physiology 15: 71-79
Leelan et al. (2003) Cytokines, Prostaglandins and Parturition—A Review. Placenta 24 supp A: S33-46.
Jenkin G, Young IR. (2004) Mechanisms responsible for parturition; the use of experimental models. Anim Reprod Sci.82-83:
Young IR, Renfree MB, Mesiano S, Shaw G, Jenkin G, Smith R (2011) The Comparative Physiology of Parturition in Mammals. In Hormones and Reproduction of Vertebrates - Vol 5: Mammals . pp Ed. Norris, D. & Lopez, K. H.. Elsevier

4. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
Birth
A dog whelps and gives birth to puppies A cow calves and give birth to a calf A sow farrows and gives birth to piglets A ewe lambs and give birth to lambs A horse foals and give birth to a foal

5. BIOL30001 Reproductive Physiology
The birth process
Parturitition: Geoff Shaw
transition:
retain & nurture fetus
 expel fetus
synchrony
parturition & fetal maturation
fetal & maternal regulation of timing
activation of myometrium
softening of cervix
timing – synchrony with fetal maturation
Johnson & Everitt Fig 13.1

6. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
Fetal maturation
lung
transition between amniotic fluid to air
structural maturation
surfactant production (cortisol induced)
circulation
placental to pulmonary gas exchange
closure of foramen ovale & ductus arteriosus
carbohydrate and fat reserves
mobilisation of liver glycogen by cortisol
fat reserves released by insulin & thyroxine until lactation established

7. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
The Myometrium
circular and longitudinal muscle layers, blood vessels and connective tissue
muscle cells hypertrophy during pregnancy
electrical connection via gap junctions leading to coordinated contractions
intracellular Ca++ activates contraction
spontaneous pacemaker activity ® excitation threshold

8. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
Hormones
progesterone & oestradiol
prostaglandins
oxytocin
nitric oxide (NO)
relaxin

9. Progesterone & oestradiol
BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
Progesterone & oestradiol
production by placenta and CL
usually ¯ P4 &  E2 at birth
P4 E2
PG ¯ 
OT receptor 
Ca++ influx 
Ca++ sequestration ­ -
gap junctions ­

10. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
Prostaglandins
E2 P4
Phospholipids
+ -
produced in endometrium, myometrium and placenta
PGF2a uterine contractions
incr. release of Ca++ from intracellular stores
PGE2 & F2a induce cervical ripening
phospholipase A2
Arachidonic acid
Cyclo-oxygenase
(COX1, COX2)
PGH2
PGE2
PGF2
PGD
PGI2
TXA2
etc.

11. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
Oxytocin
produced by
hypothalamus, released from posterior pituitary CL
uterus
induces uterine contractions
increase Ca++ influx
stimulate PG release
release stimulated by cervical stimulation - Ferguson reflex OT
neural signal
cervical
stretch

12. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
Nitric Oxide
NO - potent inhibitor of smooth muscle contraction
Myometrium
pregnancy: progesterone promotes  iNOS
shut down NO production in labour
Cervix
activation of iNOS at term
NO activates matrix metalloproteases

13. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
Relaxin
cytokine related to insulin
produced in CL - released in late gestation
softens (relaxes) connective tissue in cervix & pubic symphysis
stimulates mammary development

14. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
goat
fetal pituitary
ACTH
fetal adrenal
fetal maturation
C19 steroids
oestrogens
cortisol
Aromatase
PLACENTA
PLACENTA
maternal
neurohypophysis
PGF2
Corpus
Luteum
regression OT
Ferguson
reflex
PG synthesis
Progesterone
withdrawal
contractions
MYOMETRIUM

15. Placental steroidogenic enzymes activated by cortisol
BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw HO
Cholesterol
CH3
CH3
C=O
C=O HO O
D5-pregnenolone
Progesterone
17a-hydroxylase
CH3
CH3
C=O
C=O OH OH
Aromatase HO O
17a-OH-pregnenolone
17a-OH-progesterone
17-20-Lyase
(17-20-Desmolase) O O O HO HO O
Dehydroepiandrosterone
(DHEA)
Androstenedione
Oestrone OH OH O HO
Testosterone
Oestradiol-17b

16. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
sheep
fetal pituitary
ACTH
cortisol
incr. sensitivity to ACTH at term
fetal maturation
fetal adrenal
oestrogens
17 hydroxylase
C17-C20 lyase
Aromatase
Progesterone
PLACENTA
PLACENTA
maternal
neurohypophysis OT
Ferguson
reflex
P4 decrease
as production
redirected into E2
Progesterone
withdrawal
PG synthesis
contractions
MYOMETRIUM

17. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
Birth in humans
Somewhere on this globe, every ten seconds, there is a woman
giving birth to a child.
She must be found and stopped. --Sam Levenson

18. BIOL30001 Reproductive Physiology
human
Parturitition: Geoff Shaw
fetal pituitary
ACTH
cortisol
fetal maturation
fetal adrenal
CRF
C19 steroids (largely DHAS)
oestrogens
PLACENTA
Aromatase
no 17-hydroxylase
PLACENTA
maternal
neurohypophysis
PGF2
CL regression
Progesterone
withdrawal
PG synthesis
iNOS OT
Ferguson
reflex
MYOMETRIUM
contractions

19. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
pH 7.35
Umb Art
pH 7.2
pH 7.26
Fetal haemoglobin
Bohr effect – pH change as CO2 ex-changed increases O2 transfer
note: placenta highly metabolically active – uses 30% of O2 supplied
Ut Art
Umb Vein
Ut Vein
Johnson & Everitt Fig 12.2; table 12.1

20. Circulation before birth
BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
Circulation before birth
oxygenated blood draining from placenta mixes with depleted blood from body
Lung is fluid filled and has low O2. It has constricted arterioles restricting blood flow FO
LUNG
BODY
PLACENTA DA
Most blood shunts through foramen ovale and ductus arteriosus.

21. Circulation after birth
BIOL30001 Reproductive Physiology
Circulation after birth
Parturitition: Geoff Shaw
increased flow into Left Atrium closes flap over Foramen ovale
Oxygen opens capillaries in lung increasing blood flow
FO closes
LUNG
BODY
DA closes
increased oxygenation of blood in ductus arteriosus causes contraction and closure

22. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
indicator of lung surfactant production
Johnson & Everitt Fig 12.5

23. Actions of fetal adrenal glucocorticoids
BIOL30001 Reproductive Physiology
Actions of fetal adrenal glucocorticoids
Parturitition: Geoff Shaw
lung surfactant; water resorption central respiratory mechanisms
metabolism glucose storage and gluconeogenesis
endocrine induced insulin secretion induced adrenaline secretion conversion of T3 to T4 placental steroidogenesis
blood switch from fetal to adult haemoglobin switch haematopoiesis to bone marrow
salt balance stimulation of GFR and Na+ resorption ?activation of ANF
lactogenesis ductal-lobule-alveolar growth in pregnancy

24. BIOL30001 Reproductive Physiology
Parturitition: Geoff Shaw
placenta FO RA LA
body
lung RV LV
Ductus Arteriosus
Sensitive to O2, closes when O2 increases
Foramen Ovale
Flap valve, closes when pressure in LA>RA RA RV LA LV
body
lung DA

25. Parturition Summary
Process involves synchronised interactions between fetus and maternal system
Transition from quiescent to active uterus (↓Prog, ↑E2; NO; PGF2α; OT; Fergusson reflex)
Triggers vary between species
Fetal triggers: adrenal cortisol
Placental: PGE2; CRF
Physiological maturation of cardiovascular system: gas exchange switch from placenta to lung