Endocrinology Of Pregnancy

Question 1

Voyage of Spermatoza

Answer 1

Travels x100,000 it’s length from testis to Fallopian tube

Question 2

What does semen contain?

Answer 2

Spermatoza - 15-120million/ml
Seminal Fluid - 2-5ml
Leucocytes
Potential viruses (hep B/HIV)

Question 3

Why so much Spermatoza required?

Answer 3

1/100 of Spermatoza in ejaculate enter the cervix
1/10,000 in cervix enters ovum
So overall 1/million reach the ovum

Question 4

Seminal fluid from where?

Answer 4

Small contribution from epididymis/testis
Mainly from accessory sex glands:
-Seminal vesicles
-Prostate
-Bulbourethral glands

Question 5

What is in seminal fluid?

Answer 5

Fructose
Citric acid
Bicarbonate
Fibrinogen
Fibrinolytic enzymes

Question 6

Definition of Capacitation of Sperm

Answer 6

Achieve fertilising capability in the female reproductive tract

Question 7

3 steps of capacitation

Answer 7

1. Loss of glycoprotein ‘coat’
2. Change in surface membrane characteristics
3. Develop whiplash movements of tail

Question 8

Other factors required for capacitation of sperm

Answer 8

Takes place in ionic and proteolytic environment of the Fallopian tube
Oestrogen-dependent
Ca2+ dependent

Question 9

Acrosome reaction

Answer 9

Sperm binds to ZP3 (sperm receptor)
Ca2+ influx into sperm (stimulated by progesterone)
Release of hyaluronidase and proteolytic enzymes (from acrosome)
Sperm penetrates the Zona Pellucida (glycoprotein layer)

Question 10

Fertilisation

Answer 10

Occurs within the Fallopian tube (widest part)
Triggers cortical reaction
Cortical granules release molecules which degrade Zona Pellucida (ZP2 & 3)
Therefore prevents further sperm binding as no receptors
Haploid -> Diploid

Question 11

Development of Conceptus

Answer 11

Continues to divide as it moves down Fallopian tube to uterus (3-4days)
Receives nutrients from uterine secretions
Free-living phase can last for 9-10 days

Question 12

Implantation

Answer 12

Attachment phase: outer trophoblast cells contact uterine surface epithelium
Then
Decidualisation phase: changes in underlying uterine stromal tissue (within a few hrs)
Requires progesterone domination in the presence of oestrogen

Question 13

Attachment

Answer 13

Leukaemia inhibitory factor (LIF) from endometrial cells stimulates adhesion of blastocyst to endometrial cells
Interleukin-11 (IL11) also from endometrial cells is released into uterine fluid, and may be involved
Many other molecules involved in process (HB-EGF)

Question 14

Decidualisation

Answer 14

Endometrial changes due to progesterone

• glandular epithelial secretion
• glycogen accumulation in stromal cell cytoplasm
• growth of capillaries
• increased vascular permeability (odema)

Factors involved:
Interleukin-11 (IL11), histamine, certain prostaglandins + TGFbeta (promotes angiogenesis)

Question 15

Hormone Changes during Pregnancy

Answer 15

hCG - peaks to about 75% plasma concentration during 9 weeks then decreases
Human placental Lactotrophs and oestrogens increase gradually to about 50% plasma concentration until 40 weeks then drops at birth
Progesterone increases more steeply until about 35 weeks to 100% plasma concentration then drops then on

Question 16

Progesterone & Oestrogen Production during Pregnancy

Answer 16

First 40 days:
Produced in corpus luteum (in 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 starts to take over

Question 17

Physiological Changes in Maternal Hormones

Answer 17

Increase:
ACTH
Adrenal Steroids
Prolactin
IGF1 (stimulated by placental GH -variant)
Iodothyronines 
PTH related peptides

Decrease:
Gonadotrophins
Pituitary GH
TSH

Question 18

Endocrine Control of Partruition

Answer 18

Oxytocin with the help of Oestrogen and Progesterone stimulates uterine contraction, cervical dilatation and male ejection
Oxytocin made by posterior pituitary

Question 19

Endocrine control of Lactation

Answer 19

Suckling stimulates neural pathways to the hypothalamus and in turn to the pituitary which:

• stimulates oxytocin release from neurohypophysis (milk ejection)
• stimulates prolactin release from adenohypophysis (milk synthesis)