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