Later Foetal Development, Labour and Parturition

Question 1

In late foetal development, are the ventricles working in parallel or series?

Answer 1

parallel

Question 2

Vascular shunts bypass what circulation to close at birth?

Answer 2

pulmonary and hepatic

Question 3

Primitive air sacs form when?

Answer 3

20 weeks

Question 4

Vascularisation of lungs begins when?

Answer 4

28 weeks

Question 5

Surfactant production begins when?

Answer 5

20 weeks, upregulated towards term

Question 6

How many hours a day does foetus spend making rapid respiratory movements in REM sleep?

Answer 6

1-4 hrs

Question 7

When is endocrine pancreas become functional?

Answer 7

start of 2nd trimester

Question 8

Functional insulin from when?

Answer 8

mid 2nd trimester

Question 9

Liver glycogen in foetal development?

Answer 9

progressively deposited, accelerates towards term

Question 10

Debris and bile acids from swallowed amniotic fluid forms?

Answer 10

meconium

Question 11

When do foetal movements begin?

Answer 11

late 1st trimester

Question 12

Foetal movements are detectable by the mother around when?

Answer 12

14 weeks

Question 13

Stress response starts around?

Answer 13

18 weeks

Question 14

Thalamus cortex connections forming from?

Answer 14

24 weeks

Question 15

What state of consciousness in the foetus in during development?

Answer 15

mostly slow wave or REM sleep

Question 16

Organ maturation is co-ordinated by?

Answer 16

fetal corticosteriods

Question 17

The process of labour includes?

Answer 17

safe expulsion of foetus at correct time, expulsion of placenta and foetal membranes, period of resolution/healing to permit future reproductive events

Question 18

Labour has the characteristics of?

Answer 18

pro inflammatory reaction (immune cell infiltration and inflammatory cytokine and prostagladin secretion

Question 19

What happens in the first stage of labour?

Answer 19

contractions start, cervix dilation

Question 20

What occurs in the latent and active phases of the first stage of labour?

Answer 20

latent: slow dilation to 2-3cm
active: rapid dilation to 10cm

Question 21

What happens in the second stage of labour?

Answer 21

maximal myometrial contractions, delivery of the foetus

Question 22

What happens in the third stage of labour?

Answer 22

delivery of the placenta, expulsion of foetal membranes, postpartum repair

Question 23

Why does the cervix have high connective tissue content?

Answer 23

provides rigidity

stretch resistant

Question 24

Describe the remodelling of the cervix.

Answer 24

Bundles of collagen fibres embedded in a proteo-glycan matrix

Changes to collagen bundle structure underlie softening, but mechanism unclear.

Question 25

What changes happen to the cervix beginning from the first trimester?

Answer 25

measurable changes in compliance but retains cervical competence

Question 26

What changes happen to the cervix in the weeks and days before birth?

Answer 26

ripening: Monocyte infiltration and IL-6 and IL-8 secretion | Hylaluron deposition

Question 27

What occurs during dilation?

Answer 27

increased elasticity Increased hyaluronidase expression -> HA breakdown MMPs decrease collagen content

Question 28

What happens during post partum repair?

Answer 28

Recovery of tissue integrity and competency

Question 29

What happens to CRH levels towards the end of the pregnancy?

Answer 29

rise exponentially

Question 30

Why does CRH bioavailability increase?

Answer 30

decline in CRH binding protein levels

Question 31

CRH functions in labour?

Answer 31

promotes fetal ACTH and cortisol release Increasing cortisol drives placental production of CRH -> Positive feedback! stimulates DHEAS production by the fetal adrenal cortex -> substrate for estrogen production

Question 32

What maintains uterine relaxation during pregnancy?

Answer 32

high progesterone levels

Question 33

At term approaches what happens to progesterone isoforms?

Answer 33

switch from PR-A (activating) to PR-B/C (repressive) > functional progesterone withdrawal

Question 34

At term approaches what happens to expression of estrogen receptor alpha?

Answer 34

increases

Question 35

How does the uterus change in terms of responsiveness to oestrogen and progesterone?

Answer 35

'blinded' to progesterone action | sensitised to oestrogen action

Question 36

Where is oxytocin synthesised?

Answer 36

utero-placental tissues | pituitary

Question 37

What happens to uterine oxytocin production at the onset of labour?

Answer 37

increases sharply

Question 38

Expression increase of oxytocin is driven by?

Answer 38

increase in oestrogen

Question 39

What is the Ferguson reflex?

Answer 39

self-sustaining cycle of uterine contractions initiated by pressure at the cervix (positive feedback loop)

Question 40

Oxytocin signals through what receptor?

Answer 40

G coupled oxytocin receptor (OXTR)

Question 41

What inhibits OXTR expression pre labour?

Answer 41

progesterone

Question 42

What stimulates expression of OXTR?

Answer 42

oestrogen rise

Question 43

Functions of oxytocin?

Answer 43

Increases connectivity of myocytes in myometrium, | destabilise membrane potentials to lower threshold for contraction, enhances liberation of intracellular Ca2+ ion stores

Question 44

What primary prostagladins are synthesized during labour?

Answer 44

PGE2 PGF2 alpha PGI2

Question 45

What drives prostagladin action in the uterus?

Answer 45

rising oestrogen

Question 46

How does oestrogen drive prostagladin action?

Answer 46

activates phospholipase A2 enzyme > arachidonic acid for synthesis and stimulates OXTR > promotes PG release

Question 47

Effect of PGE2 in labour

Answer 47

cervix re-modelling: promotes leukocyte infiltration into the cervix, IL-8 release and collagen bundle re-modelling

Question 48

Effect of PGF2 alpha in labour

Answer 48

myometrial contractions: destabilises membrane potentials and promotes connectivity of myocytes (with oxytocin)

Question 49

Effect of PGI2 in labour

Answer 49

myometrium: promotes myometrial smooth muscle relaxation and relaxation of lower uterine segment.

Question 50

List factors other than prostagladins that have key effects in labour.

Answer 50

peptide hormone relaxin nitric oxide both implicated in cervix remodelling

Question 51

Describe formation of the birth canal.

Answer 51

Myometrial muscle cells form a syncytium (extensive gap junctions), brachystatic (fibres do not return to full length on relaxation) contractions start from the fundus, spread down upper segment > lower segment and cervix to be pulled up

Question 52

List the steps of foetal expulsion.

Answer 52

head engages with pelvic space > pressure causes chin to press to chest > rotates belly to mother's spine > head first > shoulders delivered sequentially > torso next

Question 53

What happens to uterus after foetal delivery?

Answer 53

rapid shrinking

Question 54

Uterine shrinking causes?

Answer 54

folding of fetal membranes, area of contact of placenta with endometrium shrinks

Question 55

How to stop foetal blood flow to placenta after birth?

Answer 55

clamp umbilical cord

Question 56

Why does uterus remain contracted after birth?

Answer 56

facilitate uterine vessel thrombosis