pregnancy, parturition and lactation Flashcards
what happens during fertilisation
-gametes transported to ampulla of oviduct
-oocyte surrounded by granulose cells
-sperm: 150-600 m vagina: capacitation in female tract, 50-100 ampulla (flagellum, contraction seminal fluid prostaglandin, cervical mucus channels)
-sperm acrosomal reaction- penetration
-oocyte activation cortical reaction leads to an increase in Ca2+: second meiotic division, prevents polyploidy
-fusion of haploid pronuclei- diploid zygote (46 chromosomes)
what are the conditions like pre-implantation
-conceptus nourished by oviduct secretions- 3 days
-isthmus SM contractions
-fluid filled cavity lined by trophectoderm layer- yolk sac
what happens in implantation
-endometrium reception of blastocyst - low estradiol to progesterone ratio (secretor phase)
-blastocyst promotes endometrial stromal cells- predecidualisation decidua (specialed mucosal lining)
-invasion of endometrium
-blastocyst trophoblastic cells: inner cytotrophoblast- single mitotic layer, differentiates into outer syncytiotrophoblast which produces hormones
what are the 4 stages of endometrial invasion
-hatching
-apposition
-adhesion
-invasion
what happens during placental development
-life support system- 120 maternal spiral arteries bring pulsatile blood
-intervillous space reduces force and velocity for exchange
-syncytiotrophoblast lacunae merge and fill with maternal blood
-cytotrphoblast and syncytiotrophoblast form villi/micorvilli projecting into maternal blood
-in mature placenta, foetal and maternal blood separated by foetal capillary endothelium, mesenchyme, cytotrophoblasts and syncytiotrophoblasts
what’s the transport between maternal and foetal blood
-substances transported are glucose (FD), AA (secondary active transport), and vitamins (AT)
-waste urea, creatine diffusion from F to M
-large molecules by receptor mediated endocytosis : LDL, hormones and antibodies
-oxygen exchange facilitated by higher affinity for oxygen of foetal haemoglobin
what are the hormonal changes during pregnancy: trimester 1
-trophoblast (then placenta): human chorionic gonadotropin (HCG), rescues corpus luteum
-as a result, corpus luteum continues secretion oestrogen and progesterone to support endometrium
what are the hormonal changes during pregnancy: trimester 2 and 3
-placenta primary hormone source (for steroid synthesis)
-human placental lactogens (human chronic somatomammotropins) coordinate fuel economy glucose to FA - energy source and ketones as well as development mammary glands
-progesterone synthesised from circulatory cholesterol
-oestrogen: placenta-foetal synthesis
what’s quiescence: parturition
-parturition stage 0
-prelude to birth (from conception to initiation of parturition)
95% of gestation
-uterus relaxed and insensitive to uterotonic hormones
-porgesterone stresses myometrial contractions
-Braxton-hicks contractions in preparation
what’s activation/ transformation in parturition
-parturition stage 1
-preparation for birth prior to labour
-foetal H-P-adrenal axis causes an increase in cortisol
-cortisol increases oestrogen and progesterone causes an increase in contractility
-oestrogen stimulates prostaglandins release which promote formation of gap junctions and softens and thins dilation of cervix
-gene expression: contraction associated proteins (CAPs)
-cervical gene expression - enzymes to hydrolyse collagen matrix for shortening. thinning and dilation
what’s stimulation/ labour/ birth in parturition
-stage 2 parturition
-increased prostaglandins levels cause myometrial contraction and cervical dilation
-increased myometrial connectivity
-increased myometrial responsiveness
-positive feedback: Ferguson reflex (neuroendocrine regulation OT), and uterine contraction stimulates prostaglandins
-stages of labour and delivery : dilation, expulsion and placental
what’s involution recovery from birth in parturition
-parturition stage 3
-haemostasis where vasoconstriction spiral arteries decrease haemorrhage
-decrease in placental oestrogen : myomerial atrophy (involution), and regression uterine vasculature
-cervix remodelling
establishment endometrial cycle 3-5 months
how is lactation involved in hormonal control
-secretory unit of breast- alveoli, surrounded by contractile myoepithelial cells and adipose tissue
-during pregnancy: oestrogen and progesterone stimulate breast growth and development, oestrogen stimulates anterior pituitary prolactin for further development but in pregnancy, oestrogen and progesterone inhibit PRL lactogenic action on breast
what happens during postpartum hormone action
-oestrogen increases cell proliferations
-PRL initiates milk production
-oxytocin (OT) increases myoepithelial contraction leading to ejection
-PRL and cortisol maintain milk production
how do neuronal and coronal systems interact to enable lactation
-PRL essential for milk production, suckling
-inhibits dopamine release from hypothalamus
-PRL from anterior pituitary
-OT from posterior pituitary
-downregulates GnRH release to inhibit ovarian cycle
