Reproduction 19 Flashcards
Describe hCG
Glycoprotein of alpha (identical to FSH, LH and TSH) and beta subunits, acts on LH receptors, maintains the corpus luteum (progesterone) and stimulates DHEA production in the fetal adrenal gland
Critical for initiation of pregnancy, synthesised by syncytiotrophoblast at around day 6-7
Released into materal ciculation
Describe the importance of progesterone in pregancy
Progesterone 1- Absolute requirement throughout pregnancy Placenta takes over production from the corpus luteum at around 6-8 weeks
Progesterone 2- progestin, Maintains pregnancy, reduces myometrial muscle excitability, decreased synthesis of proteins assiciated with contractility, maintains decidua, resets respiratory center in maternal lungs, thermogenic, increases protein breakdown, promotes aveolar cell proliferation, but inhibits lactogenic effects of hPL
Levels do not fall prior to human parturition- less efficient receptors- functional progesterone withdrawal
Describe the importance of oestrogen
Rises throughout pregnancy
Oestriol predominates (least active)
Produced cooperatively by placenta and foetus
Fetal adrenal cortex becomes highly developed and allows a high amount of oestrogen to be synthesised from conjugated (water soluble and inactive) progesterone from the placenta in the presence of androgens
Increase uterine blood flow,stimulates prolactin release form the anterior pituitary
Reduces peripheral glucose uptake, increase in cholesterol and trigycerides and deceases HDL
Increase glycogen stores and muscle mass in the myometrium
Increases endometrium contraction (ER down-regulated by prosterone
Describe human placental lactogen (hPL)
hPL produced by syncytiotrophoblast, rises as hCG falls
Large amounts in maternal blood, little in foetus
Suppresses action of insulin in the mother to aid fetal nutrition gestational diabetes
Describe prolactin (PLR)
Rises linearly during pregnancy
Oestrogen stimulates PRL release by lactotroph cells in the anterior pituitary
Help to get breast tissue ready for milk production
What are the three stages of parturition?
- Contractions begin, dilation and shortening of the cervix
- Full dilation for the cervix- delivery of the baby
- Delivery of placenta
Describe myometrial contractiltiy
At term rising oestrogen:progesterone activity increases oxytocin receptors
Oxytocin (a nonapeptide preoduced by neurohypophysis) is synthesised by the hypothalamus , secretes by the posterior pituitary and decidua- up-regulated at term because of oestrogen, lowers excitatory threshold of the myometrial muscle cells. Released in response to tactile stimulation of the cervix, operates through the neuroendocrine pathway, Ferguson reflex
ntramyometrial PGF2 alpha increase uterine contractions and cervical distension, sensed by oxytocin releasing neurones which promotes futhter contractions and PG release
Partutition requires 3 key changes: Intiating signal, co-ordinated contraction of uterine myometrium smooth muscle, cervial softening and dilation
Describe the contribution of the foetus in the timing of paturition
Maturation of fetal HPA axis-
increase in fetal glucocorticoids and corticotrophin releasing hormone (CRH- precursor of ACTH)- oestrogen and prostaglandin (arachidonic acid is 6-8 fold higher in women during labour), oestrogen:progesterone increase promotes phospholipase A2 activation and local arachidonic acid release and PGF2alpha
CRH converted to oestradiol in the placenta which metabolised to DHEAS in the maternal liver- pro-contractile myometrial effects. This stimulates initiation of labour
Describe the changes to the cervix that takes place during partuition
loosening of the collagen fibres (keratan sulphate replaces dermatan sulphate),
increased glycosaminoglycans,
increase matrix metalloproteinase production,
increase inflammatory cells and cytokine- prostaglandins soften cervix
Cervix starts to soften days/weeks before birth. PGE2 used clinically in induction of labour
Describe boobs
15-20 lobes (alveoli, blood vessels and lactiferous ducts) of glandular tissue interspaced with fibrous/adipose tissue
Alveoli- epithelial acinar cells that synthesise milk, myoepithelial cells, contract to move milk to the lactiferous ducts for ejection
Development of alveoli during puberty and deposition of fat and connective tissue
Oestrogen increases size and number of ducts, progesterone increases number of alveolar cells but inhibits lactogenic effects of hPL
hPL stimulates the development of acinar glands
Prolactin levels increase with gestation and promotes milk production
Oxytocin promotes milk ejection
Suckling increases PRL release (maintaing milk production) and oxytocin (stimulates break muscle contraction and milk ejection) release
If breast feeding isnt stimulated within first few weeks of pregnancy, prolactin levels will drop off anf breast feeding wont be able to happen.
What are the advantages of breast feeding?
Baby- protects against infection, illness and allergies, enhances development and intelligence, long term health benefits
Mother- delays fertility, reduce gynaecological cancer risk, emotional health, weight loss, osteoporosis
