Endocrinology of Pregnancy Flashcards
Where is tubular fluid reabsorbed and what controls this process?
Rete testis
Early epididymis
This is under the control of 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 these secreted nutrients and molecules?
Provide energy for the impending journey
Coat the surface of the spermatozoon (to protect them from the 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 and secretory products are added thus diluting the sperm.
Where is a vasectomy performed?
Lower end of the vas deferens
Which structures contribute to the seminal fluid?
Epididymis/testes (small contribution)
Seminal vesicle (2/3)
Prostate (1/3)
Why is there fibrinogen and fibrinolytic enzymes in the seminal fluid?
After ejaculation, the semen initially clots and then must be broken down
Describe the capability of the spermatozoa in the seminiferous tubule.
Quiescent and incapable of fertilising an ovum
Describe the capabilities of the spermatozoa in the vas deferens.
Capable of limited movement
Limited capability to fertilise an ovum
When do sperm achieve full activity and capability achieved and what is the name given to this process?
Capacitation
This occurs within the female reproductive tract
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 all these changes dependent on?
Oestrogen
Calcium
Describe the acrosome reaction.
Spermatozoon binds to ZP3 glycoprotein on the zona pellucida
Once bound to ZP3, progesterone stimulates calcium influx into the spermatozoon
This results in a calcium-dependent acrosome reaction
This enables an exposed spermatozoon recognition site to bind to ZP2
Once bound to ZP2, 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 tube
What does fertilisation result in the 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 and ZP2)
This prevents further binding of other sperm
This is also CALCIUM dependent