Talk:BGDA Practical 12 - Birth

Practical Audio

BGD Cycle A 2010 Audio - Dr Mark Hill Monday 17th May 2010 3-5pm G2G4. Note - this is a live unedited recording from the practical and may contain errors in either descriptions or content. listen Part 6 | download (2.13 Mb MP3 18:36)

Hormones	Roles
Progesterone	maintains pregnancy - initially synthesized by corpus luteum, then levels maintained by placenta hyperpolarizes myometrial cells (-65 mV), reduces excitability and conductivity Level in plasma may fall just before parturition, definitely decreases following delivery of placenta
Estrogens	Group of steroidal hormones, peak when parturition begins induce increased synthesis of actomyosin and ATP in myometrial cells alter membrane potential (-50 Mv) enhances excitation/conduction act to directly increase myometrial contraction indirectly by increasing oxytocin from pituitary gland Estriol - synthesized by fetus and placenta
Oxytocin	Peptide hormone (8aa) from maternal posterior pituitary, initiation and maintenance of labour (synthetic form labour induction) myometrium sensitivity to oxytocin (increased by estrogen, decreased by progesterone) stimulus for release - mechanical stimulation of uterus, cervix and vagina (ethanol inhibits release)
Prostaglandins	hydroxy fatty acids - sythesized by placenta, amniotic fliud contains mainly PGF2 alpha, causes myometrial contraction (also in maternal plasma) prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E2 (PGE2) - used to induce labour (intravenous, oral, intravaginal, intraamniotic) Aspirin inhibitor of PG synthesis - leads to increased duration of pregnancy

External Environment

• mainly shown in other species parturition occurs in peaceful undisturbed surroundings, stress may have an inhibitory effect on oxytocin release
• Most human births occur at night (peak at 3am) diurnal rhythm influence