Endocrinology of pregnancy

Question 1

Male reproductive tract (efferent ducts) - What induces tubular fluid reabsorption

Answer 1

Oestrogen - concentrates the sperm

Question 2

What happens in the epididymis?

Answer 2

Nutrient and glycoprotein secretion into epididymal fluid (induced by androgens)

Question 3

How many sperm reach the ovum?

Answer 3

Overall 1/million reach the sperm

Question 4

In semen how many spermatozoa are there in how much seminal fluid?

Answer 4

15-120 million/ml

2-5ml

Question 5

What is the seminal fluid made from?

Answer 5

Small contribution from - epididymis
Mainly from accessory sex glands - Seminal vesicles, prostate and bulbourethral glands; contribute fructose, fibrinogen and citric acid etc

Question 6

Define capacitation of sperm?

Answer 6

Achieve fertilising capability in the female reproductive tract
This occurs in ionic and proteolytic environments of the Fallopian tube and is oestrogen and Ca2+ dependent.

Question 7

How does capacitation occur?

Answer 7

1) Loss of glycoprotein coat
2) Change in surface membrane characteristics
3) Develop whiplash movement of tail

Question 8

What does the capacitated sperm have at the head?

Answer 8

Acrosome

Question 9

What does the acrosome bind to and what does it cause?

Answer 9

Acrosome reaction

ZP3 glyocprotein (sperm receptor) in the Zona Pellucida (glycoprotein layer). 
This causes Ca2+ influx into the sperm --> release of hyaluronidase and proteolytic enzymes from the acrosome. This allows for the penetration of the zona pellucida.

Question 10

Describe fertilisation?

Answer 10

Occurs within the fallopian tube which triggers cortical reaction.
Cortical granules release molecules which degrade the zona pellcuida, preventing furthter sperm binding (no receptors)

Haploid –> Diploid

Question 11

What is the conceptus?

Answer 11

What is formed directly after the fusion of the sperm and the egg

Question 12

How does the conceptus develop?

Answer 12

Divides as it moves down the fallopian tube to uterus (3-4 days)
Receives nutrients from uterine secretions
This free-living phase can last for 9-10 days

Question 13

Draw the development of the cenceptus?

Answer 13

Fertilized egg –> 2 cell conceptus –> 4 cell C –> 8 cell C –> morula–> blastocyst

See diagram

Question 14

Draw and label a blastocyst

Answer 14

See diagram
Inner cell mass - embryo
Trophoblast cells - chorion (placenta)

Question 15

What are the two stages of implantation?

Answer 15

Attachment phase
Decidualisation phase
This requires porgesterone dominance in the presence of oestrogen.

Leukemia Inhibitiory factor (LIF) and IL11 are key factors required for this to occur

Question 16

Define attachment phase

Answer 16

Outer trophoblast cells contact uterine surface epithelium

Question 17

Define decidualisation phase

Answer 17

Changes in the underlying uterine stromal tissue (within a few hours)

Question 18

Describe LIF?

Answer 18

Secreted from endometrial secretory glands - stimulates adhesion of blastocyst to endometrial cells

Question 19

Describe IL11?

Answer 19

Secreted from endometrial cells is released into uterine fluid, and may be involved with attachment.

Question 20

During decidualisation what endometrial changes occur due to progesterone?

Answer 20

Glandular epithelial secretion
Glycogen accumulation in stromal cell cytoplasm
Growth of capillaries
Increased vascular permeability (–> oedema)

Question 21

What factors are involved in dicidualisation?

Answer 21

IL-11, histamine, certain prostaglandins & TGFb(promotes angiogenesis)

Question 22

Where is hCG produced?

Answer 22

Human Chorionic Gonadotrophin hormone produced in the placenta

Question 23

Draw the graph showing the changes in the hormones during pregnancy

Answer 23

See diagram

Question 24

Describe the progesterone and oestrogen production during pregnancy?

Answer 24

First 40 days - produced by the corpus luteum (in the maternal ovary). Stimulated by hCG (produced by trophoblasts) which acts on LH receptors
Essential for developing fetoplacental unit
Inhibits maternal LH & FSH (-ve feedback)

From day 40 - placenta takes over

Question 25

How can you check if an egg has been produced?

Answer 25

Look via ultrasound for a corpus luteum

Look for rising levels of progesterone typically at day 21

Question 26

Draw the mother-fetus-placenta axis

Answer 26

See diagram - key thing to take away from this is that mother and fetus produce DHEAS. DHEAS acts on the placenta to produce oestradiol.

Question 27

Describe the increase in physiological changes in maternal hormones during pregnancy?

Answer 27

Increase in:
ACTH
Adrenal steroids
Prolactin - can’t track prolactinoma during pregnancy cause its naturally raised. Check visual fields
IGF-1 (stimulated by placental GH-variant)
Iodothyronines - supports the body. hCG is linked to this.
PTH related peptides - involved in Ca2+ during pregnancy.

Question 28

Describe the decrease in physiological changes in maternal hormones during pregnancy?

Answer 28

Gonadotrophins - due to the high circulating oestrogen levels - negative feedback
Pituitary GH
TSH - hCG works to drive the thyroid so you don’t need to much TSH. Share a receptor

Question 29

Draw the parturition diagram

Answer 29

Complex process - Maybe don’t need to know…
Main point - Oxytocin binds to the oxytocin receptor which increases during pregnancy leading to endometrial contraction. There are also influences from oestrogen and cortisol.

Question 30

Where is oxytocin produced?

Answer 30

In the neurohypophysis

Question 31

Describe lactation

Answer 31

Suckling (stimulus) –> neural pathway to the hypothalamus –> pituitary
Neurohypophysis –> oxytocin –> ejection of the milk
Adenohypophysis –> prolactin –> synthesis of the milk