Menstrual Cycle and Pregnancy

Question 1

What stages is the menstrual cycle split into?

Answer 1

Ovarian cycle and uterine cycle driven by hormone level changes

Question 2

What makes up the Ovarian cycle?

Answer 2

follicular phase

Ovulation

Luteal phase

Question 3

What compromises the Uterine cycle?

Answer 3

(Endometrial cycle)

Menstrual phase

Proliferative phase

Secretory phase

Question 4

What Feedback loops and hormones regulate the menstrual cycle?

Answer 4

Driven by feedback loops between hypothalamic GnRH, Pituitary LH and FSH, and ovarian oestrogen, progesterone, inhibin and activin release

Question 5

What induces Tubular fluid reabsorption resulting in concentrated fluid? ( male )

Answer 5

Oestrogen

Question 6

What induces Fructose and glycoprotein secretion in epididymal fluid

Answer 6

Androgens

Question 7

What is the capacitation of sperm?

Answer 7

Achieve fertilising capability in the female reproductive tract by:

Loss of glycoprotein coat
Change in surface membrane characteristics
Develops whiplash movements of tail

Question 8

Where does Capacitation take place and why?

Answer 8

Ionic and proteolytic environment of the fallopian tube

• Oestrogen dependent
• Ca2+ dependent

Question 9

What reaction takes place at the Acrosome and Zona Pellucida?

Answer 9

Sperm binds to the ZP3 glycoprotein sperm receptor

Ca2+ influxed into sperm by progesterone

Release of hyaluronidase and proteolytic enzymes from acrosome

Spermatozoon penetrates the Zona pellucida

Question 10

Where does Fertilisation take place?

Answer 10

Fallopian tube

Question 11

What does fertilisation trigger?

Answer 11

Cortical reaction

Cortical granules release molecules which degrade Zona Pellucida e.g. ZP2, ZP3 preventing further binding

Haploid develops into Diploid

Question 12

How does the zygote develop into a Conceptus ( Embryo which zygotic membranes )

Answer 12

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 ~ 9-10 days

8 cell conceptus which form a morula

Inner cell mass will form the embryo

Question 13

Describe Implantation?

Answer 13

Attachment phase: outer trophoblast cells contact uterine surface epithelium

THEN

Decidualisation phase: changes in underlying uterine stromal tissue (within a few hours)

Requires progesterone domination in the presence of oestrogen

Question 14

How does the Blastocyst attach to the endometrial lining?

Answer 14

IL-11 promote attachment alongside Leukaemia inhibitory factor.

Question 15

Describe Attachment?

Answer 15

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 (e.g. HB-EGF)

Question 16

What is Decidualisation?

Answer 16

Endometrial changes due to progesterone:

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

Factors involved:
Interleukin-11 (IL11), histamine, certain prostaglandins & TGFb (TGFb promotes angiogenesis)

Question 17

How does hCG change over the duration of the 40 weeks of pregnancy?

Answer 17

hCG peaks before 10 weeks and then falls to low levels

Question 18

How does Progesterone levels change throughout pregnancy?

Answer 18

Increases steadily until 30-40 weeks where it drops

Question 19

How do Oestrogens and Human placental Lactogen change throughout pregnancy?

Answer 19

Lower levels then progesterone, Lactogen lower thean Oestrogens

Steadily increase from start to week 40 then drops

Question 20

What do progesterone and Oestrogen do during pregnancy?

Answer 20

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 21

Where is Progesterone and Oestrogen formed during pregnancy?

Answer 21

In the placenta post day 40

• Placenta makes progesterone from cholesterol – pregnenolone- prog

Question 22

What is the main substrate for Oestrogens during pregnancy?

Answer 22

DHEAS which can be made by mother AND fetus

Question 23

What maternal hormones increase during pregnancy?

Answer 23

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

Question 24

What maternal hormones decrease during pregnancy?

Answer 24

Gonadotrophins
Pituitary GH
TSH

Question 25

Describe Endocrine control of partruition ( labour )?

Answer 25

Main hormone is oxytocin from post pituitary:

• Uterine contraction with increased numbers of oxytocin receptors in late pregnancy
• Cervical dilation
• Milk ejection

Contributions from cortisol and oestrogen
Milk production is prolactin

Oxytocin receptorsare expressed by the myoepithelial cells of the mammary gland, and in both the myometrium and endometrium of theuterusat the end of pregnancy.