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BRS Year 2 > Pregnancy, parturition and late foetal development > Flashcards

Pregnancy, parturition and late foetal development Flashcards

(98 cards)

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1
Q

early embryo nutrition?

A

Histiotrophic
Derivation of nutrients from the breakdown of surrounding tissues
Breakdown of maternal capillaries
Glands within the endometrium provide uterine milk

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2
Q

What happens between first and second trimester?

A

Rapid increase in rate of growth

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3
Q

what happens in first trimester

A

limited growth due to histiotrophic nutrition

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4
Q

what is the nutrition in second trimester

A

haemotrophic

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5
Q

how is histitrophic nutrition supported in the early implantation of the embryo

A

Syncytiotrophoblast breaks down maternal cells and uses their products to support embryo development
breakdown of maternal capillaries + uterine gland secretions exposes syncytiotrophoblast to maternal blood to derive nutrients from

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6
Q

what is the amnion

A

Derivative of epiblast - extraembryonic structure
First foetal membrane
Forms the amniotic cavity that goes on to become the amniotic sac

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7
Q

two key foetal membranes

A

amnion

chorion

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8
Q

what is the chorion

A

outer membrane surrounding whole conceptus unit

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9
Q

what is the connecting stalk

A

extra embryonic tissues which grows from the embryo and connects the conceptus with the chorion

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10
Q

What are the trophoblastic lacunae?

A

Large spaces filled with maternal blood formed by breakdown of maternal capillaries and uterine glands
Become intervillous spaces aka maternal blood spaces

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11
Q

How are trophoblastic lacunae formed?

A

Breakdown of maternal capillaries and glands
Lumens of the glands and capillaries start to fuse
Create a continuous space where maternal blood can flow

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12
Q

what are the foetal membranes and their function

A

extraembryonic tissues that form a tough but flexible sac which encapsulates the fetus and forms the basis of the maternal-fetal interface

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13
Q

what happens in the 5th week to amniotic fluid

A

Amnion begins to secrete amniotic fluid from 5th week – forms a fluid filled sac that encapsulates and protects the fetus

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14
Q

chorion main features

A

Formed from yolk sac derivatives and the trophoblast
highly vascularized
forms chorionic villi

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15
Q

what are chorionic villi (cell and function)

A

cytotrophoblast outgrowths from the chorion that form the basis of the fetal side of the placenta

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16
Q

how is the amniotic sac expanded?

A

fluid accumulation forces the amnion into contact with the chorion, which fuse, forming the amniotic sac

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17
Q

layers of amniotic sac

A

amnion on the inside

chorion on the outside

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18
Q

what is the allantois

A

yolk sac outgrowth
grows along connecting stalk embryo-chorion
becomes coated in mesoderm and vascularises
FORMS UMBILICAL CORD

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19
Q

what forms the umbilical cord

A

connecting stalk
allantois
plus mesoderm cells

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20
Q

what are cytotrophoblast cells

A

Important in the development of the placenta

form finger-like projections through syncitiotrophoblast layer Into maternal endometrium (primary chorionic villi)

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21
Q

fingerlike projections of cytotrophoblast into endometrium

A

primary chorionic villi

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22
Q

role of chorionic villi

A

Provide substantial surface area for exchange (gases and nutrients)

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23
Q

phases of chorionic villi development

A

primary secondary tertiary

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24
Q

primary phase of chorionic villi development

A

outgrowth of the cytotrophoblast and branching of these extensions

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25
seconary phase of chorionic villi development
growth of the fetal mesoderm into the primary villi
26
tertiary phase of chorionic villi development
growth of the umbilical artery and umbilical vein into the villus mesoderm
27
structure of terminal chorionic villi
convoluted blood vessel comes up through the villus, coated in trophoblast cells Surrounded by maternal blood
28
what do the knots of terminal chorionic villi allow
slows blood flow | enables exchange between maternal and foetal blood
29
how do the villi change from early to late pregnancy
thick to thin | reduced diffusion distance in late pregnancy
30
blood supply of endometrium
UTERINE ARTERY - ARCUATE arteries - RADIAL arteries - BASAL arteries - SPIRAL arteries
31
maternal blood supply changes in menstrual cycle
basal arteries spiralise if no implantation - regression of spiral As implantation - stabilise
32
what is spiral artery remodelling
as spiral arteries develop the extra-villi trophoblast cells invade, break down smooth muscle and endothelium of arteries EVT cells coat inside of spiral arteries turns spiral artery into low pressure high capacity conduit for maternal blood
33
what is the process of spiral artery remodelling called
conversion
34
what do issues in conversion cause
preeclampsia | intra-uterine growth retardation
35
structure of placenta
maternal arteries and veins supply intervillous space chorionic villi from foetus act as exchange surface half moon shape
36
how does nutrient exchange occur across placenta
Diffusion Facilitated diffusion Active transport
37
how is oxygen exchanged across the placenta
diffusion gradient | high maternal O2 tension, low foetal
38
how is glucose exchanged across the placenta
facilitated diffusion | by foetal trophoblast cells and maternal transporters
39
how is water exchanged across the placenta
diffusion some local hydrostatic gradients some crosses chorion-amnion
40
how are electrolytes exchanged across the placenta
diffusion and active transport
41
how is calcium exchanged across the placenta
active transport by magnesium ATPase calcium pump
42
transport of amino acids across placenta
reduced maternal urea excretion | active transport
43
changes in maternal cardiac system
CO increased peripheral resistance decreased blood volume increases - erythrocytes and plasma
44
changes to maternal resp system
pulmonary ventilation increases almost half fold
45
features of foetal blood O2
foetal O2 tension low O2 content and sats similar to maternal blood embryonic/foetal haemoglobins have greater affinity for O2 than maternal haemoglobin
46
how does the circulatory system mature in foetuses
placenta is main site of gas exchange ventricles act in parallel pulmonary and hepatic circulation bypassed until birth
47
maturation of respiratory system
Primitive air sacs form in lungs around 20 weeks, vascularization from 28 Surfactant production begins around week 20, upregulated towards term foetus makes rapid respiratory movements during REM sleep, practice for breathing reflex for once it leaves the uterus. - important for diaphragm dev.
48
maturation of GI tract
endocrine pancreas function from 2nd trimester - insulin mid 2T liver glycogen progressively deposited – accelerates towards term Large amounts of amniotic fluid swallowed –debris and bile acids form meconium
49
what is the meconium
first stool delivered just after birth | formed from amniotic fluid debris and bile acids
50
maturation of nervous system
movement from late 1T stress response starts at 18wk no conscious wakefulness - mostly slow wave or REM sleep
51
what initiates final maturation f organ systems
increase in foetal corticosteroids
52
aims of labour
safe expulsion of foetus placenta, foetal membranes healing for future reproduction
53
what chemical has key role in timing and sequence of labour
prostaglandins
54
stages of partituition
quiescence activation stimulation involution
55
phase 1 of partiution
prelude | contractile unresponsiveness, cervical softening
56
phase 2 of partuition
Preparation for labour Uterine preparedness for labour Cervical ripening
57
phase 3 partiuition
Process of labour Uterine contraction Cervical dilation Foetal and placental expulsion
58
phase 4 partiuition
Uterine involution Cervical repair Breast feeding
59
first stage of labour
contractions start | cervical dilation
60
stages of first stage of labour
Latent Phase: Slow dilation of the cervix to 2-3cm Active Phase: Rapid dilation of the cervix to 10cm
61
second stage of labour
foetus delivery
62
third stage of labour
Delivery of the placenta and foetal membranes | Post-partum repair
63
cervix structure and role in labour and pregnancy
High connective tissue content: Provides rigidity Stretch resistant Bundles of collagen fibres embedded in a proteoglycan matrix Changes to collagen bundle structure underlie softening
64
what is the first cervical change and when is it
softening - first trimester
65
when does cervical ripening occur
weeks/days before birth monocyte infiltration and IL-6 IL-8 secretion hylaluron deposition
66
how does cervical dilation occur
hyaluronidase enzyme expression increase | hyaluronic acid degrades, matrix metalloproteinases decrease collagen content
67
role of corticotrophin releasing hormone in pregnancy
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
68
what are progesterone levels in pregnancy and why
high | maintains uterine relaxation
69
what changes occur in oestrogen and progesterone signalling close to delivery
As term approaches, switch from PR-A isoforms (activating) to PR-B and PR-C (repressive) expressed in the uterus -> functional prog. withdrawal High levels of P but the receptor changes blind uterus to it Rise in oestrogen alpha receptor - Uterus sensitised to action of oestrogen
70
production of oxytocin in labour
Uterine oxytocin production increases sharply at onset of labour Expression increase is driven by increase in oestrogen levels Release promoted by stretch receptors as the foetus bears down on the cervix, stretching it -> Ferguson reflex
71
what is the ferguson reflex
foetus bares down on cervix, stretch receptors cause increased release of oxytocin
72
oxytocin signalling
via g-coupled oxytocin receptor | OXTR
73
functions of oxytocin in labour
Increases connectivity of myocytes in myometrium (syncytium) Destabilise membrane potentials to lower threshold for contraction Enhances liberation of intracellular Ca2+ ion stores
74
how does a rise in oestrogen drive prostaglandin action
Rising oestrogen activates phospholipase A2 enzyme, generating more arachidonic acid for PG synthesis oestrogen stimulation of oxytocin receptor OXGR expression promotes PG release
75
PGE2 role in labour
cervix re-modelling | Promotes leukocyte infiltration into the cervix, IL-8 release and collagen bundle re-modelling
76
PGF2 alpha role in labour
myometrial contractions | Destabilises membrane potentials and promotes connectivity of myocytes (with Oxytocin)
77
role of PGI2 in labour
myometrium | Promotes myometrial smooth muscle relaxation and relaxation of lower uterine segnment
78
regulation of labour process
foetal CRH - cortisol placenta CRH + DHEAS (oestrogen produced) oestrogen acts on myometrium promoting the expression of OXTR and local production of oxytocin Uterus becomes sensitive to produce the pituitary production of maternal oxytocin - CONTRACTIONS + prostaglandin synth PGs ripen and soften cervix
79
process of myometrial contractions
Myometrial muscle cells form syncytium (extensive gap junctions) Contractions start from the fundus, spread down upper segment Muscle contractions are brachystatic (fibres dont return to full length on relaxation) therefore Lower segment and cervix pulled up forming birth canal
80
how does foetal head position change towards delivery
Head engages with pelvic space 34-38wks | Pressure on fetus causes chin to press against chest (flexion)
81
how is foetus expelled
``` Fetus rotates (belly to mother’s spine Head expelled first after cervix dilates Shoulders delivered sequentially (upper first) followed by torso. ```
82
what happens after foetal expulsion
placenta expulsion Uterine shrinkage also causes folding of fetal membranes – peel off the endometrium Clamping of the umbilical cord after birth stops fetal blood flow to placenta -> villi collapse Hematoma formation between decidua and placenta Contractions expel placenta and fetal tissues
83
how does the uterus undergo repair
Uterus remains contracted after delivery to facilitate uterine vessel thrombosis. Uterine involution and cervix repair restore non-pregnant state Shielding uterus from commensural bacteria Restore endometrial cyclicity in response to hormones
84
how is preeclampsia diagnosed
During routine check ups: Check BP Urine tests Blood tests
85
maternal risk factors for preeclampsia
``` Age Obesity First pregnancy Previous pregnancy with pre-eclampsia/Family history Gestational hypertension or previous hypertension PCOS Renal disease Diabetes Subfertility Autoimmune disease ```
86
early onset preeclampsia
less than 34 wk foetal and maternal symptoms changes in placental structure
87
late onset preeclampsia
over 34wk mostly maternal symptoms less placental structural changes
88
symptoms of preeclampsia
high bp when previously normotensive headaches proteinuria upper abdominal pain (less common)
89
risks to foetus in preeclampsia
reduced growth stillbirth neonatal respiratory distress syndrome preterm birth
90
risks to mother in preeclampsia
HELLP syndrome pulmonary oedema eclampsia placental abruption
91
pathophysiology of preeclampsia
failure of normal trophoblast invasion (only in decidual layer) maladaption of maternal spiral arterioles - placental perfusion restricted
92
factors associated with preeclampsia
PLFG - proangiogenic, released in large amounts by placenta | Flt1 (soluble VEGFR1) - receptor for VEGF like factors, limits their bioavailability
93
role of factors in preeclampsia
excess Flt1 leads to reduction of available pro-angiogenic factors in maternal circulation, resulting in endothelial dysfunction
94
use of PLGR tests alone in PE
triage test | rules out PE in the next 14 days
95
use of sFlt1:PLGF ratio in PE
under 38 rules out PE | over 38 has increased risk of PE
96
how is PE managed
only cured by placenta delivery - if over 37wk, deliver, under 34, keep, in between is case by case anithypertensives corticosteroids if under 34wk for lung development before delivery
97
long term impacts of PE
Elevated risk of CV disease, t2DM and renal disease | Roughly 1/8 risk of having pre-eclampsia in next pregnancy (greater if early onset)
98
prevention of pre-eclampsia
weight loss exercise - regardless of PE baby aspirin for high risk groups prevents early onset

BRS Year 2 (67 decks)

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