endocrinology of pregnancy Flashcards
tubular fluid reabsorption in rete testis and epididymis is under what control?
oestrogen
nutrient and glycoprotein secretion into the epididymal fluid is under what control?
androgen
what are the functions of these secretions?
- provide energy for jounrey
- coat surface of spermatozoa (protection)
where is semen ejaculated to? how much spermatozoa enter cervix?
- ejaculated into vagina or cervical canal
- 1%
what does sperm consist of?
- spermatozoa
- seminal fluid
- leucocytes (so potentially viruses, e.g. Hep B, HIV)
where is seminal fluid produced?
- epididymis/testes (small contribution)
- accessory sex glands (major contribution)
what are these accessory sex glands?
- seminal vesicles (produce fructose and fibrinogen)
- prostrate (produce citric acid)
- ampulla
- bulbourethral
what is capacitation of sperm?
- in seminiferous tubule, spermatozoa are incapable of fertilizing an ovum
- in vas deferens, they are capable of movement but have little capability of fertilisation
- full activity, spermatozoa must undergo capacitation in oviduct
what is the order of capacitation?
- loss of glycoprotein coat
- change in surface membrane characteristics
- whiplash movements
what is needed for capacitation?
- oestrogen dependant
- requires Ca2+ for all activities
what does fertilisation occur in?
fallopian tubes
what does fertilisation result in?
- expulsion of second polar body (of ovum)
- leads to immediate zona reaction (degradation of ZP3 coat)
- this prevents further binding (Ca dependent)
What is the Ca influx into the sperm stimulated by?
- progesterone
- and as a result of G-protein mediated action following the binding of sperm to ZP3
what is the cortical reaction?
breakdown of zona pellucida by granules containing digestive enzymes to break down coat
when does the zygote start dividing?
once diploidy is established
what is the Ca-dependent acrosome reaction?
- enables capacitated spermatozoa to bind to and pennetrate the zona pellucida by releasing haluronidase
what is the conceptus?
fertilised ovum
what then happens to the conceptus?
- continues to divide as it travels down the oviduct (3-4 days)
- receieve nutrients from uterine secretions
- conceptus first compacts to an 8-16 cell morula
- then it becomes a blastocyst
- then transferred to uterus at this stage facilitated by inc. progesterone: oestrogen ratio
describe a blastocyst
2 separate cell populations
- inner mass (becomes embryo)
- outer trophoblast (becomes chorion)
what does implantation involve?
- attachment phase: outer trophoblast cells contact uterine epithelium
- decidualisation: of underlying stromal tissue
what does implantation require?
progesterone domination in presence of oestrogen
what does leukaemia inhibitory factor from endometrium stimulate?
adhesion of blastocyst to endometrium
IL-11 also involved
what is decidalisation?
invasion of underlying uterine stromal tissue by outer trophectoderm cells of blastocyst
what happens in decidualisation within hours?
- inc. vascular permeability in invasion region (oedema)
- localised changes in intracellular composition (glycogen accumulation in cytoplasm)
- progessive sprouting and growth of capillaries (decidulaisation reaction)
what are the factors invovled in decidualisation?
- IL-11
- histamine
- prostaglandins
- TGF-beta (angiogenesis)
what happens in the first 5-6 weeks of pregnancy?
- maternal ovaries release gonadal steroids
- circulating progesterone and oestradiol conc are high and rising
- this inhibits release of materal LH and FSH
as LH and FSH are inhibited, what is the stimulatory role on corpus luteum taken over by?
hCG produced by developing blastocyst
what happens from day 40 of pregnancy?
- ovariectomy has no effect on pregnancy
- role of corpus luteum taken over by foetalplacental unit
what maternal hormones increase in pregnancy?
- ACTH (pregnany activated stress axis)
- prolactin (suppresses GnRH)
- iodothyronines (pregnancy inc. metabolic rate, driven by hCG not TSH, so TSH falls)
- adrenal steroids (more ACTH so more cortisol)
- PTHrp (parathormone related peptide, more Ca required for lactation)
what maternal hormones decrease in pregnancy?
- gonadotrophins
- TSH (falls as hCG stimulates high T4)
- hCG (placental variant inc)
generally, what happens in parturition?
oxytocin –> raised intracellular calcium –> contraction
what does contraction occur by?
- by calcmodulin activating calmodulin-myosin kinase which cintracts actin-myosin
what does oestrogen stimulate that leads to raised intracellular Ca?
- oestrogen stimulates phospholipase A2
- stimuates arachidonic acid to PGF2a production
- raises intracellular Ca from microsomes
- Ca can also enter from outside
what hormones are involved in lactation?
- oxytocin stimulates milk ejection
- prolactin stimulates milk synthesus
