Endocrinology of pregnancy

Question 1

In relation to the size of a sperm cell, how long is the journey of a sperm from testes to oviduct?

Answer 1

100,000 times the length of a sperm (<1/10^6 make it)

Question 2

What happens to most of the tubular fluid in men?

Answer 2

It reabsorbed within the rate testis and early epididymis under the control of oestrogen

Question 3

What produces tubular fluid?

Answer 3

Sertoli cells

Question 4

What controls secretion of nutrients and other molecules into the epididymal fluid?

Answer 4

Androgens

Question 5

What are the nutrients and other molecules for?

Answer 5

Provide journey for impending journey and coat the surface of the spermatozoon

Question 6

Where does a vasectomy occur?

Answer 6

Vas deferens at the bottom end

Question 7

How does concentration of spermatozoa compare in vas deferens compared to later on?

Answer 7

It is much higher at the vas deferens as lots of fluid is added along the way

Question 8

What does semen consist of?

Answer 8

Spermatozoa
Seminal fluid
Leucocytes
Viruses (potentially)

Question 9

What are some examples of components of seminal fluid that come from epidydimis/testis?

Answer 9

Inositol, carnitine, glycerylphosphorylcholine

Question 10

What are some examples of components of seminal fluid that come from accessory sex glands (seminal vesicle and prostate)?

Answer 10

Fructose
Fibrinogen
Citric acid
Fibrinogenase and fibrinolytic enzymes

Question 11

Why do you get fibrinogen and fibrinolytic enzymes in semen?

Answer 11

After ejaculation, the semen initially clots and then must be broken down

Question 12

What are spermatozoa in the seminiferous tubule like?

Answer 12

Quiescent and incapable of fertilising an ovum

Question 13

What are spermatozoa in the vas deferens like?

Answer 13

Capable of limited movement (whiplash)

Limited ability to fertilise

Question 14

When is full activity and fertilising capability achieved?

Answer 14

When in the female reproductive tract

Question 15

What is the process of reaching full activity and fertilising capability called?

Answer 15

Capacitation

Question 16

What percentage of spermatozoa in ejaculate make it to the cervix?

Answer 16

1%

Question 17

How do the spermatozoa achieve capacitation? (3 things)

Answer 17

Loss of glycoprotein coat
Change in surface membrane characteristics
Whiplash movements of the tail

Question 18

Why can the spermatozoa lose the glycoprotein coat?

Answer 18

It has a protective function in the vagina but once in the uterus it isn’t necessary

Question 19

What two things are all the components of capacitation reliable on?

Answer 19

Oestrogen and calcium

Question 20

What happens to a sperm as it approaches an ovum?

Answer 20

There are changes in the membrane

Question 21

What does a spermatozoon bind to?

Answer 21

ZP3 glycoprotein on zona pellucida

Question 22

What happens after the spermatozoon binds to ZP3?

Answer 22

Progesterone stimulates the calcium influx into the spermatozoon

Question 23

What does the calcium influx lead to in fertilisation?

Answer 23

Calcium dependent acrosome reaction

Question 24

What does the calcium dependent acrosome reaction enable?

Answer 24

An exposed spermatozoon recognition site to bind to a second glycoprotein (ZP2)

Question 25

What happens once ZP2 has bound?

Answer 25

The acrosome releases its enzymes allowing penetration of the zona pellucida so that the head of the spermatozoon can enter the ovum

Question 26

Where does fertilisation normally occur?

Answer 26

Fallopian tubes

Question 27

What does fertilisation lead to?

Answer 27

Expulsion of the second polar body and the zonal reaction

Question 28

What is the zonal reaction?

Answer 28

Cortical granules release molecules which degrade the zona pellucida, this prevents further binding of other sperm. This is also calcium dependent

Question 29

What is the conceptus?

Answer 29

The product of the zygote starting to divide (baby early days)

Question 30

What happens to the conceptus as it moves from fallopian tubes to uterus?

Answer 30

It continues to divide

Question 31

How long does it take for the conceptus to travel from fallopian tubes to the uterus?

Answer 31

3-4 days

Question 32

How does the developing conceptus receive its nutrients until implantation?

Answer 32

Uterine secretions

Question 33

How long does the free living phase last (between formation and implantation)?

Answer 33

9-10 days

Question 34

While this occurs, the woman is in her luteal phase, what does this mean?

Answer 34

There will be high oestrogen and progesterone

Question 35

What does the conceptus first compact to form?

Answer 35

8-16 cell morula

Question 36

What does the 8-16 cell morula then become?

Answer 36

A blastocyst

Question 37

What are the two parts of the blastocyst and what do they become?

Answer 37

An inner cell mass- becomes the embryo | Trophectoderm- becomes the chorion which becomes the placenta

Question 38

What facilitates the transfer to the uterus?

Answer 38

Increasing progesterone:oestrogen ratio due to the luteal phase

Question 39

What is the reason for implantation?

Answer 39

Establishing a system for getting nutrients form the mother to all cells in the embryo

Question 40

What does the initial attachment phase consist of?

Answer 40

Outer trophoblast cells making contact with the uterine surface epithelium

Question 41

What is the decidua?

Answer 41

Thick layer of modified mucous membrane which lines the uterus during pregnancy and is shed with afterbirth

Question 42

When does decidualisation of the underlying stromal tissue occur?

Answer 42

Within a few hours of implantation

Question 43

Which two molecules are of particular importance in attachment?

Answer 43

``` Leukaemia inhibitory factor (LIF) Interleukin 11 (IL-11) ```

Question 44

Where does leukaemia inhibitory factor come from?

Answer 44

Endometrial secretory glands

Question 45

What does leukaemia inhibitory factor do?

Answer 45

Stimulation adhesion of the blastocyst to the endometrial cells

Question 46

Where does interleukin-11 come from?

Answer 46

Endometrial cells

Question 47

What is interleukin-11 released into?

Answer 47

Uterine fluid

Question 48

What is the decidualisation reaction?

Answer 48

Invasion of the underlying uterine stromal tissue by the trophoblast cells of the blastocyst

Question 49

What happens within hours due to the decidualisation reaction?

Answer 49

Increased vascular permeability in the invasion region | Localised changes in intracellular composition and progressive sprouting and growth of capillaries

Question 50

What factors are involved in the decidualisation reaction?

Answer 50

Mainly IL-11 Histamine Certain prostaglandins TGFbeta- promotes angiogenesis

Question 51

When does hCG reach a peak?

Answer 51

8 weeks

Question 52

When is hCG vital and why?

Answer 52

First 6 weeks as its job is to replace LH

Question 53

What happens in terms of hormones that leads to menstruation?

Answer 53

Levels of oestrogen and progesterone fall

Question 54

Why is hCG released during pregnancy?

Answer 54

It is needed to maintain the stimulation of oestrogen and progesterone

Question 55

What produces hCG?

Answer 55

Trophoblast cells

Question 56

How does hCG work?

Answer 56

It can bind to LH receptors on corpus luteum hence replacing the effects of LH

Question 57

Why are the ovaries no longer necessary in a pregnancy after 5 weeks?

Answer 57

The placenta will have taken over production of the hormones

Question 58

What happens to oestrogen and progesterone levels throughout pregnancy?

Answer 58

They increase and until the end, progesterone remains the dominant influence

Question 59

What is human placental lactogen?

Answer 59

It is produced by the placenta Growth hormone Prolactin like effects

Question 60

What are the three components important in providing steroids?

Answer 60

Mother Foetus Placenta

Question 61

What does the mother provide in terms of steroids?

Answer 61

The precursors

Question 62

What is the most common precursor?

Answer 62

Pregnenolone which leads to progesterone

Question 63

What causes steroid production in the foetus?

Answer 63

Progesterone

Question 64

What precursor does the foetal and maternal adrenals produce?

Answer 64

Dehydroepiandrosterone sulfate (DHEAS)

Question 65

What is DHEAS taken up by the placenta to produce?

Answer 65

Oestradiol and small amounts of oestrone

Question 66

What is the main oestrogen of pregnancy?

Answer 66

Oestriol

Question 67

If you wanted to look at the health of the baby, which oestrogen would you look at?

Answer 67

Oestriol because its source is completely foetal

Question 68

How is oestriol formed?

Answer 68

It comes from the conjugation of DHEAS in the foetal liver to form 16alpha-hydroxy DHEAS which then goes to the placenta which deconjugates it and uses it to form estriol

Question 69

What happens to most maternal hormones during pregnancy?

Answer 69

They increase

Question 70

What happens to the pituitary during pregnancy?

Answer 70

It enlarges

Question 71

What is responsible for the action of parturition?

Answer 71

Contraction of actin and myosin filaments

Question 72

What does the contraction of the filaments (parturition) require?

Answer 72

Calcium

Question 73

Why is oestrogen stimulating the production of prostaglandins important for parturition?

Answer 73

The prostaglandins stimulate the production and release of calcium into the cytoplasm from intracellular stores

Question 74

What effect does progesterone have in relation to parturition?

Answer 74

Opposite effect to oestrogen Inhibits prostaglandin synthesis Inhibits oestrogen receptors

Question 75

At parturition, oxytocin will be released, what effect will this have?

Answer 75

It will bind to its receptor and open calcium channels allowing calcium ions to move in from outside

Question 76

What does prolactin do?

Answer 76

Promotes milk synthesis

Question 77

What does oxytocin do?

Answer 77

Promotes milk ejection

Question 78

How are prolactin and oxytocin linked neurologically?

Answer 78

They have the same neuroendocrine reflex