Unit 4.2 Day 29 Learning Objectives

Parturition and Lactation

parturition definition

giving birth

(exact order of events not well understood)

parturition hormones

relaxin

progesterone

estrogen

prostaglandins

oxytocin

other

parturition: relaxin functions

preps birth canal but inhibits myometrial activity

relaxes pubis symphysis (from cartilaginous to more fluid/flex. structure (ligament))

parturition: relaxin structure

protein

2 peptide chains

disulfide bridges

(sim. to insulin)

parturition: relaxin source

corpus luteum

placenta

parturition: relaxin profile

peaks at 12 weeks + steady decline into plateau (1/2 of peak)

parturition: estrogens functions

inc. prostaglandin (PG) prod.

inc. receptors for OT on uterine musculature

inc. OT prod. in hyothal.

inc. secretion in neurohypophysis

allows for myometrial excitability

parturition: progesterone functions/levels

(earlier prevents uterine contractions)

drops for parturition

signaled by OT + prostaglandins

parturition: prostaglandins functions

luteolytic factor breaks down corpus luteum

inhibits progesterone secretion

act to ripen cervix + change membrane structure + contract myometrium

parturition: prostaglandins come from

fetal membranes (amnion + chorion)

parturition: prostaglandins structure

unsaturated carboxylic acids

consisting of 20 carbon skeleton w/ 5 member ring

parturition: oxytocin functions

uterine contractions

pos. feedback to pit

milk release, orgasm, maternal nurturing, pair-bonding

parturition: oxytocin pathway

head of fetus pushes against cervix

nerve impulse from cervix sent to brain

brain stims. pit gland to secrete oxytocin

oxytocin carried in bloodstream to uterus

oxytocin stims uterine contractions + pushes fetus toward cervix

parturition: oxytocin hormone profile

inc during early labor

peak + rapid increase in late labor

drops after

parturition: oxytocin as a H of neurohypophysis

NOT synthesized here

stores H precursor from hypothalamus

parturition: other (hormone stuff)

placental prolactin

autonomic motor neurons

fetal adrenal cortex: glucocorticoids + adrenocorticotropic H (ACTH)

corticotropin releasing H (CRH) from uterus

lactation functions

provide nutrition + immune protection to young after birth

helps gestational parent’s uterine contractions

prom. gestational parent-young bonding

lactation anatomy of placental mammals

glands + ductile system

develops during pregnancy

stim by: estrogens, progesterone, PRL, GCs/GH, placental lactogen

lactation: milk production + secretion stimulated by

E2

GCs

GH

insulin

placental lactogen

relaxin

PRL

lactation: milk production + secretion inhibited by

progesterone

lactation prevents

ovarian cycling

milk letdown reflex (oxytocin)

suckling stims nerve in breasts

nerve impulses sent to hypothalamus

hypothal sends impulse to post pit

oxytocin released

muscle contract + squeeze out milk