11: Endocrinology of pregnancy Flashcards
What hormone induces tubular reabsorption in the male reproductive tract?
Oestrogen
Concentrates the sperm
What hormone induces nutrient and glycoprotein secretion into the epididymal fluid?
Androgens
How many sperm in semen?
15-120 million/ml
How much seminal fluid in semen?
2-5 ml
How many sperm reach the egg?
1 in a million
What parts of the male reproductive system make the seminal fluid?
Mostly from accessory sex glands:
- Seminal vesicles
- Prostate
- Bulbourethral glands
Some contribution from epididymis/testis
Give 3 ways in which sperm cells achieve capacitation
- Loss of glycoprotein coat
- Change in surface membrane characteristics
- Develop WHIPLASH movements of tail
Where does capacitation take place and what is required for it?
Occurs in ionic & proteolytic environment in Fallopian tube
Need oestrogen + calcium
What is the acrosome reaction?
Mechanism by which sperm penetrates the Zona Pellucida of ovum
- Sperm binds to ZP3 glycoprotein receptor on egg
- This causes Ca2+ influx into sperm (stimulated by progesterone)
- Release of hyaluronidase & proteolytic enzymes from the acrosome which breaks down Zona pellucida
What happens during fertilisation?
Occurs in fallopian tube
Fertilisation triggers CORTICAL reaction:
Cortical granules within the egg release molecules that degrade the Zona Pellucida (including ZP2&3 receptors).
This prevents further sperm from binding to the egg
Egg turns from haploid to DIPLOID (since sperm provides father’s set of chromosomes)
This egg is now a 1-cell ZYGOTE
Where does the conceptus get its nutrients from?
Uterine secretions
How long does the free-living phase last? (phase before attaching to endometrium)
9-10 days
Describe the divisions of the conceptus as it moves down the fallopian tube to the uterus
1-cell zygote (fertilised egg)
2 cell conceptus
4 cell conceptus
8 cell conceptus
Then COMPACTION occurs and forms the MORULA
Morula develops into a BLASTOCYST
Describe the structure of blastocyst
Trophoblast cells on the outside (which will later form the chorion)
Inner cell mass (which develops into the embryo)
Blastocoelic cavity
What are the 2 steps of implantation?
- Attachment phase: Trophoblast cells contact the uterine surface epithelium
- Decidualisation phase: Changes in underlying uterine stromal tissue
What 2 things are required for implantation to occur?
Progesterone domination + oestrogen
Describe the attachment phase
- Leukemia Inhibitory Factor (LIF) = released from endometrial secretory glands - stimulates ADHESION of blastocyst to endometrial cells
- IL-11 = Also from endometrial cells, released into uterine fluid
What happens in the decidualisation phase?
Endometrial changes due to progesterone
- Glandular epithelial secretion
- Glycogen accumulation in stromal cell cytoplasm
- Growth of capillaries
- Increased vascular permeability
What factors other than progesterone are involved in the decidualisation phase?
IL-11
Histamine
Other prostoglandins
TGF-beta (promotes angiogenesis)
What is hCG and where is it produced?
Human Chorionic Gonadotrophin
Produced by the placenta
This is what we test for in urine pregnancy tests
After conception, where is progesterone produced?
First 40 days in Corpus Luteum (maternal ovary)
This is stimulated by hCG (produced by trophoblasts) which bind to LH receptors
From day 40, placenta takes over (luteoplacental shift)
What else does hCG do during pregnancy?
Drives the release of oestrogen
Inhibits maternal FSH/LH
What hormones are increased during pregnancy?
ACTH Adrenal steroids Prolactin IGF1 (Placenta releases GH variant) Iodothyronines PTH related peptides
What hormones are decreased during pregnancy?
Gonadotrophins (due to high oestrogen -> negative feedback)
Pituitary GH
TSH
