Endocrinology of Pregnancy Flashcards
Where is tubular fluid reabsorbed and what controls this process?
Rete testis
Early epididymis
Induced by oestrogen
Where do you find oestrogen within the male reproductive tract?
Tubular fluid produced by sertoli cells
What stimulates the release of nutrients and other molecules (e.g. glycoproteins) into the epididymal fluid?
Androgens
What are the roles of androgen induced secreted nutrients and molecules?
Nutrients provide energy for impending journey
Glycoproteins coat surface of the spermatozoon (to protect from hostile environment)
Within which part of the male reproductive tract is fluid reabsorbed and secretory products put in?
Epididymis
Why is the concentration of sperm in the vas deferens higher than further down the reproductive tract?
Further down the reproductive tract, other fluids + secretory products are added thus diluting the sperm.
Which structures contribute to the seminal fluid?
Epididymis/testes (small contribution)
Seminal vesicle (2/3)
Prostate (1/3)
Bulbourethral glands
What is semen comprised of?
Spermatazoa
Seminal fluid
Leucocytes
Potential viruses
When do sperm achieve full activity and what is the name given to this process?
Capacitation
Occurs within ionic + proteolytic environment of Fallopian tube
What 3 changes take place in capacitation?
Loss of glycoprotein coat
Change in surface membrane characteristics (leading to acrosome reaction when in close proximity to the ovum)
Whiplash movements of the tail
What are capacitation changes dependent on?
Oestrogen
Calcium
Describe the acrosome reaction.
Sperm binds to ZP3 glycoprotein on zona pellucida
Once bound, progesterone stimulates Ca2+ influx into the sperm
Causes release of hyaluronidase + proteolytic enzymes from acrosome
Results in penetration of the zona pellucida
Where does fertilisation normally occur? What does fertilisation result in the expulsion of?
Fallopian tube
Expulsion of Second polar body
The zonal reaction immediately follows fertilisation. Describe the zonal reaction.
Cortical granules release molecules that degrade the zona pellucida (including ZP3 + ZP2)
Prevents further binding of other sperm
Ca2+ dependent
The cell is now diploid
How does the conceptus receives nutrients before implantation? Describe the conceptus at this point
Uterine secretions provide nutrients
Continues to divide as it moves down Fallopian tube
How long is this free-living phase of the conceptus?
9-10 days
In what stage of the menstrual cycle does the development of the conceptus occur?
Luteal phase– oestrogen + progesterone are high
What does the conceptus compact to form?
8-16 cells morula
What are the two parts of the blastocyst?
Inner cell mass: becomes the embryo
Trophectoderm: becomes the chorion (which becomes the placenta)
What hormonal change facilitates the transfer of the conceptus to the uterus?
Increasing progesterone: oestrogen ratio
What is a decidua?
Thick layer of modified mucous membrane, which lines the uterus during pregnancy + is shed after birth
What hormone environment is required for decidualisation phase of implantation?
Progesterone dominance in the presence of oestrogen
State 2 molecules that are of particular importance in implantation. Mention which cells produce these molecules.
Leukaemia inhibitory factor (LIF)
Produced by endometrial secretory glands
Stimulates adhesion of blastocyst to endometrial cells
IL-11
Also released from endometrial cells + into uterine fluid
Also may be involved
In decidualisation, what endometrial changes due to progesterone occur?
Glandular epithelial secretion
Glycogen accumulation in stromal cell cytoplasm
Increased vascular permeability in the invasion region, associated with oedema of tissues
Growth of capillaries
Which chemical factors are involved in decidualisation?
Mainly IL-11
Histamine
Certain prostaglandins
TGF-beta (promotes angiogenesis)
What is the role of hCG and when does it peak?
Peaks at 8 weeks + is particularly important in 1st 6 weeks
Mimics LH by binding to LH receptors on the corpus luteum + stimulating the production of oestrogen + progesterone
Produced by trophoblast cells
What change takes place after about 6 weeks?
Role of hormone production is transferred from the corpus luteum (stimulated by hCG) to the placenta
Describe how oestrogen and progesterone levels change throughout pregnancy.
Oestrogen + progesterone levels continue to rise through pregnancy with progesterone always being the dominant influence
What is the role of human placental lactogen?
Involved in changes in metabolism
Causes insulin resistance so mother has higher glucose levels
Promotes nutrients going to baby
Which steroid precursor tends to be provided by the mother for the foetus?
Pregnenolone
Which androgen is formed by the maternal and foetal adrenals? This is used as a precursor for oestrogen production.
Dehydroepiandrosterone Sulphate (DHEAS)
Which oestrogens are produced by the placenta using DHEAS from the mother and foetus?
Oestradiol
Oestrone
Oestradiol + Oestrone aren’t a good measure of foetal health. Explain why.
These oestrogens are dependent on precursor production from the both the foetal + maternal adrenals.
Therefore, it is not a good measure of foetal health.
What is the main oestrogen of pregnancy? Describe how it is produced.
OESTRIOL
DHEAS from the foetal adrenals is conjugated in the foetal liver to form 16-alpha-hydroxy DHEAS
16-alpha-hydroxy DHEAS is then de-conjugated in the placenta + used to produce oestriol
Describe how maternal hormones change in pregnancy.
Most increase (pituitary becomes enlarged): ACTH Corticotrophin Prolactin IGF1 Iodothyronines Adrenal steroids PTH related peptides Hormones that decrease: Gonadotrophins Pituitary GH (because placental GH variant increases towards term) TSH
What biochemical change is required for contraction of the uterus during parturition?
Increase in intracellular Ca2+ concentration
Describe how oestrogen increases the chance of contraction.
Oestrogen binds to oestrogen receptors + triggers synthesis of prostaglandins within the endometrial cells.
Prostaglandins stimulate the release of Ca2+ from intracellular stores.
Describe how oxytocin increases the chance of contraction.
Oxytocin binds to its receptor on the endometrial cell + opens Ca2+ channels, allowing Ca2+ ions to move in from outside
Describe the effect of progesterone on the contraction process.
Progesterone keeps the effects of oestrogen under control
by inhibiting oestrogen receptors + the production of prostaglandins
What change occurs when the foetus reaches a particular size, which is crucial for contraction to take place?
A switch in steroid synthesis from progesterone synthesis to oestrogen synthesis
Leads to oestrogen dominance –> prostaglandin production –> Ca2+ release from intracellular stores –> promotion of muscle contraction
What 2 hormones are involved in milk production and milk ejection?
Prolactin: milk production
Oxytocin: milk ejection
Both have a similar neuroendocrine reflex arc stimulated by suckling
What are the 2 phases of implantation? Describe them
Attachment phase: Outer trophoblast cells contact uterine surface epithelium
Decidualisation phase: changes in underlying uterine stromal tissue
List 3 key roles of Oxytocin
Uterine contraction
Cervical dilation
Milk ejection
Which hormone is produced by the foetus around the time of partruition?
Cortisol
