11. Endocrinology of pregnancy Flashcards
Which cells make spermatozoa?
Sertoli cells
Which cells make testosterone?
Leydig cells
What is oestrogen required for in men and what can aromatase deficiency lead to?
- Tubular fluid reabsorption
- Bones
- Therefore, aromatase deficiency can lead to infertility, osteoporosis and being tall
What can aromatase deficiency lead to in females?
Virilisation
• Hirsutism
• Deepening voice
• Amenorrhoea
Where is most tubular fluid reabsorbed?
- Within the rete testis and early epididymis
* Under oestrogen (produced by sertoli cells)
What are secretory products, how are they induced and what do they do?
- Products e.g. fructose + glycoproteins, vital for the maturation process
- Induced by androgens
- Secreted into epididymal fluid
- Provide energy
- Coat the spermatozoa - protection
What proportion of spermatozoa reach the ovum?
< 1/10^6
What does semen consist of?
- Spermatozoa (15-120million/ml)
- Seminal fluid (2-5ml)
- Leucocytes
- Potentially viruses
What proportion of spermatozoa enter the cervix and the ovum?
• 1/100 enter the cervix
• 1/10,000 from cervix to ovum, so:
- 1/1 million reach the ovum
Where (and how) is seminal fluid produced?
Accessory sex glands
• Seminal vesicles
• Prostate
• Bulbourethral glands
- Concentrated using androgens
- Given nutrients and glycoproteins using oestrogens
- Small contribution from epididymis and testes
How does function of the spermatozoa compare in the seminiferous tubule and vas deferens?
- Seminiferous tubule - quiescent and incapable of fertilising an ovum
- Vas deferens - limited movement, limited capability for fertilising ovum
When/where do spermatozoa reach full activity?
• Once within the female reproductive tract
- ionic + proteolytic environment of the fallopian tube
• Capacitation:
- lose glycoprotein coat
- change in surface membrane characteristics
- develop whiplash movements of tail
• Oestrogen-dependent
• Ca2+ dependent
How does the movement of sperm in the female reproductive tract compare to the male?
- Male - muscle contractions
* Female - mobilise themselves
What is the acrosome reaction?
• Sperm acrosome binds to ZP3 (glycoprotein receptor)
• Ca2+ influx into sperm (stimulated by progesterone)
• Release of hyaluronidase (breaks down polysaccharides + proteolytic enzymes)
• Spermatozoon can penetrate the Zona pellucida oocyte and get straight to the egg
- cortical reaction - cortical granules release molecules to degrade Zona pellucida, blocking more sperm binding
What is the Zona pellucida?
Glycoprotein membrane surrounding the plasma membrane of the oocyte
What happens to the polar bodies in fertilisation?
- Expulsion of second polar body (haploid)
- Chromosome are evenly divided between the resultant 2 cells
- Cytoplasma is divided unevenly - ovum retains cytoplasm and last polar body degenerates
How long does it take for the fertilised egg to move from the Fallopian tube to the uterus, and where does it receive nutrients from?
- 3-4 days
- Nutrients from uterine secretions
- Can remain in the free-living phase for 9-10 days
- Inner cells receive less and less nutrients
- Occurs in the luteal phase - oestrogen and progesterone are high
What is compaction?
• 8-cell conceptus compacts to form an 8-16 cell morula
What does a blastocyst comprise?
- Inner cell mass, which becomes the embryo
* Outer trophoblast cells, which become the chorion then the placenta
What change in the hormones facilitates transfer of the blastocyst to the uterus?
Increasing the progesterone:oestrogen ratio (luteal phase) (progesterone domination in the presence of oestrogen)
What are the 2 phases of implantation?
• Attachment phase - outer trophoblast cells make contact with the uterine surface epithelium - establishing a system to get nutrients
• Decidualisation phase
- changes of the underlying uterine stromal tissue
- glandular epithelial secretion
- growth of capillaries
- decidua lines the uterus during pregnancy
- IL-11 involved
Which 2 molecules are important in the attachment phase and why?
• Leukaemia inhibitory factor (LIF)
- from endometrial secretory glands (and blastocyst?)
- Stimulates adhesion to endometrial cells
• Interleukin-11
- also released from endometrial cells
- released into uterine fluid
Give some examples of LIF and IL-11 stimulators
- LIF stimulators - TGF, TNF, leptin, progesterone
* IL-11 stimulators - IL1, TNF, TGF, PGE2
Which hormone suddenly surges during pregnancy and why is this significant?
- hCG (produced by trophoblasts)
- Initially takes over the role of LH - acts on LH receptors
- Produced in the placenta
- Can be measured in a urine pregnancy test 2 weeks after conception (earlier in a blood test)
(oestrogen, progesterone and human placental lactogen also increase)
