Endocrinology of Pregnancy Flashcards
Where is tubular fluid reabsorbed and what controls this process?
Tubular fluid reabsorbed in the efferent ducts (vasa efferentia)
- This is induced by oestrogen
- This acts to concentrate the sperm prior to entering the epididymis
NOTE:
The tubular fluid produced by the sertoli cells in the seminiferous tubules functions to:
- Provide nutrition for the developing sperm
- Provides a means of transport to carry the develpoing sperm to the epididymis
What takes place in the epididymis and what controls this process?
In the epididymis, nutrients (e.g. fructose) and glycoproteins are secreted into the epididymal fluid
- This is stimulated by androgens
NOTE: Epididymis is where the sperm mature and attain their motility
What is ejaculation?
Ejection of semen from the body
What does semen consist of?
- Spermatozoa (15-120 million/ml)
- Seminal fluid (2-5ml)
- Leucocytes
- Potentially viruses e.g. hepatitis B, HIV (if the man is infected)
What are the proportions of sperm that reach different parts of the female reporoductive tract after ejaculation?
- 1/100 of spermatozoa in ejaculate enter the cervix
- 1/10,000 cervix to ovum
- Overall 1/million reach ovum
Which structures contribute to the production of the seminal fluid?
Small contibution from:
- Testis (seminiferous tubules, rete testis - essentially the part before the epididymis)
- Epididymis
Mainly from accessory sex glands:
- Seminal vesicles
- Prostate gland
- Bulbourethral glands
What is capacitation of sperm?
This is when sperm achieve fertilising capability
- Takes place in the female reproductive tract
What 3 changes take place in capacitation?
- Loss of glycoprotein coat
- Change in surface membrane characteristics
- This allows the acrosome reaction when in close proximity to the ovum
- Change in membrane → increased permeability to Ca2+
- Whiplash movements of the tail
Where exactly does capacitation take place and what is it dependent on?
Takes place in ionic & proteolytic environment of the Fallopian tube
Dependent on:
- Oestrogen
- Calcium
Describe the acrosome reaction.
- The capacitated sperm binds to ZP3 (sperm receptor)
- Once bound to ZP3, progesterone stimulates calcium influx into the sperm
- Hyaluronidase & proteolytic enzymes are released from acrosome
- This allows the spermatozoon to penetrate the Zona Pellucida (glycoportein layer surrounding egg)
Where does fertilisation normally occur?
Fallopian tube
What does fertilisation result in the formation of?
Second meiotic division
- There is unequal distribution of cytoplam
- Cell with cytoplasm and chromosomes = ovum
- Cell with just chromosomes = polar body
- This polar body is then expelled
Describe the cortical reaction.
The cortical reaction is triggered by fertilisation
- Cortical granules release molecules that degrade the zona pellucida (including ZP3 and ZP2)
- This prevents further binding of other sperm
- As ZP3 and ZP2 are sperm glycoprotein receptors present in the zona pellicuda
- So their degradation prevents further sperm binding as there are no receptors
- The nuclei fuse: haploid → diploid
Describe how the conceptus develops before implantation
- Continues to divide as it moves down Fallopian tube to uterus (3-4 days)
- Receives nutrients from uterine secretions
- This free-living phase can last for approx. 9-10 days
Describe the process of implantation.
Attachment phase: outer trophoblast cells contact uterine surface epithelium
THEN
Decidualisation phase: changes in underlying uterine stromal tissue (within a few hours)
NOTES:
- Stroma = the part of the tissue which has a structural or connective role (i.e. parts which are not specific to the function of the tissue = everything except parenchyma)
- e.g. connective tissue, BVs, nerves etc.
- Blatocyst:
- Trophoblast → placenta
- Inner cell mass → embryo