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Reproductive system > Lecture 19- Foetal development > Flashcards

Lecture 19- Foetal development Flashcards

1
Q

The fetal period

A
  • occurs after the embryonic period
  • Growth and physiological maturation of structures created during the (v much shorter) embryonic period
  • Period involving preparing for the transition to independent living after birth
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2
Q

pre-embyonic period

A

between weeks 1-2 (blastocyst)

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3
Q

embyronic period

A

WEEK 3- 9

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4
Q

fetal period

A

weeks 9-38

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5
Q

pregnancy weeks calculated form of

A

last menstrual period

i.e. conception weeks +2, so derm is 40 weeks

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6
Q

Pattern of growth during embryonic development

A
  • Embryonic period is characterised by intense activity–>organogenetic period
  • But absolute growth is very small
    • Except placenta!
    • Growth and weight gain accelerate in fetal period
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7
Q

what is used to assess gorwth

A

crown-rump lenght (CRL) and weight

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8
Q
  • Crown-rump length (CRL)
A

increases rapidly in pre-embryonic, embryonic and early fetal periods

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9
Q
  • Weight gain during development
A
  • slow at first, then increases rapidly in mid- and late fetal periods
    • Embryo- intense morphogenesis and differentiation, little wight gain, placental growth is most significant
    • Early fetus- protein deposition
    • Late fetus- adipose deposition
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10
Q

Antenatal assessment of fetal wellbeing

A
  • Fetal movements
    • Asking the mother if she has noticed changes in movement
  • Regular measurements of uterine expansion
    • Symphysis-fundal height
  • Ultrasound scan
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11
Q

Obstetric ultrasound scan (USS)

A
  • Safe
  • Can be used early in pregnancy to calculate age
    • Also to rule out ectopic, the number of foetuses’ etc
  • Routinely carried out at 20 weeks
    • Assess fetal growth
    • Fetal anomalies
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12
Q

Estimation of fetal age based on 2 factors

A
  • LMP- last menstrual period
    • Prone to inaccuracy
  • Developmental criteria
    • Allow accurate estimation of fetal age
      • Size e.g. CRL
      • Growth curves
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13
Q

estimation of fetal age in trimester 1

A

Crown rump length

  • Highly accurate when measuring between 7 and 13 weeks to date the pregnancy and estimate EDD
  • Scan in T1 to check location, number and viability (heart beat)
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14
Q

estimation of fetal age in the 2 and 3 trimester

A

Biparietal diameter

  • Distance between the parietal bones of the fetal skull
  • Used in combination with other measurements to date pregnancy’s in T3 and T4

Abdominal cirucmferene and femur length

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15
Q

3- or 4-D USS

A
  • New wave of obstetric ultrasonography
  • Not currently replacing standard USS

Great at detecting potential congenital anomalies

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16
Q

classification of birth weights

A
  • 3500g considered average
  • <2500g suggests growth restriction
  • >4500g is marcosomnia (maternal diabetes)
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17
Q

The importance of accurate dating

  • Babies can have low birth-weight because
A
  • They are premature
  • Constitutionally small
    • Small mother= small baby
  • Suffered growth restriction (USS designed to pick this up)
    • Neonatal morbidity and mortality
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18
Q

development of the respiratory system: the lungs develop relatively

A

late

  • Not needed during embryonic or foetal life
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19
Q

in embryonic development which parts of the repsiratory system are created

A

bronchopulmonary tree

20
Q

in the fetal period which parts of the respiratory system are developed

A
  • Functional specialisation occurs in the fetal period
  • Major implications for pre-term surivival
21
Q

lungs are derived from

A

primitive gut tube (same as endoderm as GI tract)

22
Q

respiratory system development: Week 8-16

A

pseudo glandular stage

  • Duct system begins to form within the bronchopulmonary segments created during embryonic period
    • Bronchioles
23
Q

respiratory system development: week 16- 28

A
  • Formation of respiratory bronchioles
  • Budding from bronchioles formed during the pseudoglandular stage
24
Q

respiratory system development: Weeks 26- term

A
  • Terminal sac begins to bud from resp bronchioles
  • Differentiation of Type I and II penuomocytes
25
Q

The lungs during T2 and T3

A
  • Gas exchange conducted at the placenta but lungs must be prepared to assume full burden at birth
  • Breathing movements to practice during foetal development
    • Conditioning of the respiratory musculature
    • Breathing movement means amniotic fluid goes into the lungs à crucial for normal developmentà promotes differentiation
26
Q

viability depends massively on the

A

how far the resp system is developed

27
Q
  • Viability is only possibility once the lungs have entered the
A
  • terminal sac stage of development >24 weeks
    • Can have abortion up till then
28
Q

Respiratory distress syndrome

A
  • Insufficient surfactant production by type 2 pneumocytes
  • If pre-term is unavoidable or inevitable
    • Glucocorticoid treatment (of the mother)
    • Increases surfactant production in fetus
29
Q

respiratory distress syndrome pathophysiology

A

The primary cause of RDS is inadequate pulmonary surfactant. The structurally immature and surfactant-deficient lung has ↓ compliance and a tendency to atelectasis; other factors in preterm infants that ↑ the risk of atelectasis are decreased alveolar radius and weak chest wall

30
Q

The cardiovascular system

*

A
  • Fetal cardiovascular system is arranged to ensure oxygenated blood collected by umbilical veins at the placenta and is circulated around the fetus
  • Definitive fetal H/R is achieved at around 15 weeks
31
Q

Fetal bradycardia associated with

A

fetal demise

32
Q

fetal kidney function begins in

A

week 10

33
Q
A
34
Q
  • Fetal urine major contributor of
A
  • amniotic fluid volume
35
Q

oligohydramnios

A

too little amniotic fluid due to:

  • placental insufficiency–> not enough blood provided to be filtered by the kidney
  • fetal renal impairment
36
Q

polyhydramnios

A

too much amniotic fluid due to

  • fetal abnormality such as inability to swallow
37
Q

Fetal kidney function not necessary for survival in utero, but without it there is

A

oligohydramnios (lower than normal amniotic fluid)

38
Q

the nervous system is the

A
  • First to begin development and last to finish
39
Q

nervous system development in the foetal period

A
  • Corticospinal tracts required for coordinated voluntary movements begin to form in the 4th month
  • Myelination of brain only begins in 9th month
    • E.g. corticospinal tract myelination incomplete at birth, as evidenced by increasing infant mobility in the 1st year
40
Q

Sensory and motor system

A
  • No movement until 8th week
  • At 8th week- startle movement
  • Thereafter a large repertoire of movements develop
    • Practising for post-natal life e.g. suckling (sucking thumb), breathing
41
Q
  • ‘quickening’
A
  • Maternal awareness of fetal movement’s from 17 weeks onwards
  • Felt earlier in subsequent pregnancy
  • Low cost, simple method of antepartum fetal surveillance
  • Reveal those foetuses requiring follow up
42
Q

cerebellar devlopment and corticospinal tracts being to form at

A

week 16

43
Q

myelination of spinal cord begins at

A

week 20

44
Q

charactersitic gyri and sulci appear as cerebellar hemispheres frow larger than the skull

A

week 28

45
Q

myelination begins in the brain

A

week 36

Reproductive system (28 decks)

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