Endocrinology of pregnancy Flashcards
In relation to the size of a sperm cell, how long is the journey of a sperm from testes to oviduct?
100,000 times the length of a sperm (<1/10^6 make it)
What happens to most of the tubular fluid in men?
It reabsorbed within the rate testis and early epididymis under the control of oestrogen
What produces tubular fluid?
Sertoli cells
What controls secretion of nutrients and other molecules into the epididymal fluid?
Androgens
What are the nutrients and other molecules for?
Provide journey for impending journey and coat the surface of the spermatozoon
Where does a vasectomy occur?
Vas deferens at the bottom end
How does concentration of spermatozoa compare in vas deferens compared to later on?
It is much higher at the vas deferens as lots of fluid is added along the way
What does semen consist of?
Spermatozoa
Seminal fluid
Leucocytes
Viruses (potentially)
Seminal fluid from
Mainly from seminal vesicles, prostrate, bulbourethral glands
small contribution from::
-epididymis/testis
What are spermatozoa in the seminiferous tubule like?
Quiescent and incapable of fertilising an ovum
What are spermatozoa in the vas deferens like?
Capable of limited movement (whiplash)
Limited ability to fertilise
When is full activity and fertilising capability achieved?
When in the female reproductive tract
What is the process of reaching full activity and fertilising capability called?
Capacitation
What percentage of spermatozoa in ejaculate make it to the cervix?
1%
How do the spermatozoa achieve capacitation? (3 things)
Loss of glycoprotein coat
Change in surface membrane characteristics
Whiplash movements of the tail
Why can the spermatozoa lose the glycoprotein coat?
It has a protective function in the vagina but once in the uterus it isn’t necessary
Where does capacitation occur
What two things are all the components of capacitation reliable on?
In ionic and proteolytic environment of fallopian tubes
Oestrogen and calcium
What happens to a sperm as it approaches an ovum?
There are changes in the membrane
What does a spermatozoon bind to?
ZP3 glycoprotein on zona pellucida
What happens after the spermatozoon binds to ZP3?
Progesterone stimulates the calcium influx into the spermatozoon
What does the calcium influx lead to in fertilisation?
Calcium dependent acrosome reaction
What does the calcium dependent acrosome reaction enable?
An exposed spermatozoon recognition site to bind to a second glycoprotein (ZP2)
What happens once ZP2 has bound?
The acrosome releases its enzymes allowing penetration of the zona pellucida so that the head of the spermatozoon can enter the ovum
Where does fertilisation normally occur?
Fallopian tubes
What does fertilisation lead to?
Expulsion of the second polar body and the zonal reaction
What is the zonal reaction?
Cortical granules release molecules which degrade the zona pellucida, this prevents further binding of other sperm. This is also calcium dependent
What is the conceptus?
The product of the zygote starting to divide (baby early days)
What happens to the conceptus as it moves from fallopian tubes to uterus?
It continues to divide
How long does it take for the conceptus to travel from fallopian tubes to the uterus?
3-4 days
How does the developing conceptus receive its nutrients until implantation?
Uterine secretions
How long does the free living phase last (between formation and implantation)?
9-10 days
While this occurs, the woman is in her luteal phase, what does this mean?
There will be high oestrogen and progesterone
What does the conceptus first compact to form?
8-16 cell morula
What does the 8-16 cell morula then become?
A blastocyst
What are the two parts of the blastocyst and what do they become?
An inner cell mass- becomes the embryo
Trophectoderm- becomes the chorion which becomes the placenta
What facilitates the transfer to the uterus?
Increasing progesterone:oestrogen ratio due to the luteal phase
What is the reason for implantation?
Establishing a system for getting nutrients form the mother to all cells in the embryo
What does the initial attachment phase consist of?
Outer trophoblast cells making contact with the uterine surface epithelium
What is the decidua?
Thick layer of modified mucous membrane which lines the uterus during pregnancy and is shed with afterbirth
When does decidualisation of the underlying stromal tissue occur?
Within a few hours of implantation
Which two molecules are of particular importance in attachment?
Leukaemia inhibitory factor (LIF) Interleukin 11 (IL-11)
Where does leukaemia inhibitory factor come from?
Endometrial secretory glands
What does leukaemia inhibitory factor do?
Stimulation adhesion of the blastocyst to the endometrial cells
Where does interleukin-11 come from?
Endometrial cells
What is interleukin-11 released into?
Uterine fluid
What is the decidualisation reaction?
Invasion of the underlying uterine stromal tissue by the trophoblast cells of the blastocyst
What happens within hours due to the decidualisation reaction?
Increased vascular permeability in the invasion region
Localised changes in intracellular composition and progressive sprouting and growth of capillaries
What factors are involved in the decidualisation reaction?
Mainly IL-11
Histamine
Certain prostaglandins
TGFbeta- promotes angiogenesis
When does hCG reach a peak?
8 weeks
When is hCG vital and why?
First 6 weeks as its job is to replace LH
What happens in terms of hormones that leads to menstruation?
Levels of oestrogen and progesterone fall
Why is hCG released during pregnancy?
It is needed to maintain the stimulation of oestrogen and progesterone
What produces hCG?
Trophoblast cells
How does hCG work?
It can bind to LH receptors on corpus luteum hence replacing the effects of LH
Why are the ovaries no longer necessary in a pregnancy after 5 weeks?
The placenta will have taken over production of the hormones
What happens to oestrogen and progesterone levels throughout pregnancy?
They increase and until the end, progesterone remains the dominant influence
What is human placental lactogen?
It is produced by the placenta
Growth hormone
Prolactin like effects
What are the three components important in providing steroids?
Mother
Foetus
Placenta
What does the mother provide in terms of steroids?
The precursors
What is the most common precursor?
Pregnenolone which leads to progesterone
What causes steroid production in the foetus?
Progesterone
What precursor does the foetal and maternal adrenals produce?
Dehydroepiandrosterone sulfate (DHEAS)
What is DHEAS taken up by the placenta to produce?
Oestradiol and small amounts of oestrone
What is the main oestrogen of pregnancy?
Oestriol
If you wanted to look at the health of the baby, which oestrogen would you look at?
Oestriol because its source is completely foetal
How is oestriol formed?
It comes from the conjugation of DHEAS in the foetal liver to form 16alpha-hydroxy DHEAS which then goes to the placenta which deconjugates it and uses it to form estriol
What happens to most maternal hormones during pregnancy?
They increase
What happens to the pituitary during pregnancy?
It enlarges
What is responsible for the action of parturition?
Contraction of actin and myosin filaments
What does the contraction of the filaments (parturition) require?
Calcium
Why is oestrogen stimulating the production of prostaglandins important for parturition?
The prostaglandins stimulate the production and release of calcium into the cytoplasm from intracellular stores
What effect does progesterone have in relation to parturition?
Opposite effect to oestrogen
Inhibits prostaglandin synthesis
Inhibits oestrogen receptors
At parturition, oxytocin will be released, what effect will this have?
It will bind to its receptor and open calcium channels allowing calcium ions to move in from outside
What does prolactin do?
Promotes milk synthesis
What does oxytocin do?
Promotes milk ejection
How are prolactin and oxytocin linked neurologically?
They have the same neuroendocrine reflex
