7: Foetal Growth & Development Flashcards

1
Q

When is the foetal period?

A

From: end of week 8

To: birth

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2
Q

What are the 3 processes of the foetal period?

A
  1. Rapid growth (increased cell size + number)
  2. Continued tissue + organ differentiation
  3. Relative slow down in growth of head compared to rest of body
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3
Q

When is the embryonic period?

A

First 8 weeks

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4
Q

What happens in the embyronic period? (3 things)

A
  1. Morphogenesis (Crown Rump Length increases rapidly
  2. Growth @ placenta
  3. Organogenetic activity

MGO

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5
Q

What does foetal survival depend on in terms of the respiratory system? (2 things)

A
  1. Presence of thin-walled air sacs for gas exchange
  2. Presence of surfactant to reduce surface tension + allow air sac to expand
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6
Q

What are the 4 stages of lung maturation?

A
  1. Pseudoglandular (week 8 - 16)
  2. Canalicular (week 16 - 26)
  3. Terminal Sac (week 26 - term)
  4. Alveolar (late foetal - 8 years old)

Puff Cones Till Afterlife

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7
Q

Are the lungs viable in the pseudoglandular stage of lung maturation?

A

No

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8
Q

Are their air sac in the pseudoglandular stage of lung maturation?

A

No

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9
Q

Where are the airways formed up to in the pseudoglandular stage of lung maturation?

A

Ony as far as Terminal Branches

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10
Q

Are the lungs viable in the canalicular stage of lung maturation?

A

Maybe at end

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11
Q

What is formed in the canalicular stage of lung maturation?

A

Respiratory bronchioles

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12
Q

What happens in the terminal sac stage of lung maturation? (3 things)

A
  1. Terminal sacs bud off from respiratory bronchioles
  2. Cells differentiate → Type 1 & 2 Pneumocytes (allow diffusion)
  3. Surfactant produced
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13
Q

What happens in the alveolar stage of lung maturation? (late foetal - 8 years old)

A

95% of alveoli formed post-natally

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14
Q

What changes occur to the lungs at birth? (4 things)

A
  1. Lungs filled with amniotic fluid
  2. Most is expelled @ vaginal birth and rest is absorbed
  3. At first breath
  • Pulmonary resistance decreases
  • Alveoli open
  1. Blood flow increases in pulmonary vessels
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15
Q

What does placental progesterone promote?

A

Foetal corticosteroid production (vital for CVS)

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16
Q

When does the foetal thryoid gland begin to work?

A

Week 12

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17
Q

What do the thyroid hormones help develop? (2 things)

A
  1. Hair
  2. Bone
  3. CNS

HBC (like HSBC innit)

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18
Q

What does the foetal liver store?

A

A lot of glycogen

Reflected in changes in foetal abdominal circumference

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19
Q

When is the definitive heart rate acheived?

A

Week 15

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20
Q

How are heart beats heard in Week 8, Week 12, and Weeks 18 - 20?

A

Week 8: via Transvaginal US

Week 12: via Doppler Stethoscope

Weeks 18 - 20: via Plain Stethoscope

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21
Q

What is the heart beat at week 8 (measured by transvaginal US) used for?

A

To rule out ectopic pregnancy

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22
Q

What is the average heart beat at term?

A

140 - 160 bpm

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23
Q

When is the kidney finished ascending and ready to function?

A

Week 10

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24
Q

What happens to the kidney at week 10?

A

Becomes a major contributor to amniotic fluid

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25
Q

What is the route of urine in the foetus? (3 steps)

A
  1. Urine enters bladder
  2. Bladder empties into amniotic fluid
  3. Amniotic fluid swallowed by foetus
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26
Q

What is the frequency of the bladder emptying and filling?

A

Every 40-60 minutes

Can be seen on US to asses foetal urinary function

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27
Q

What is oligohydramnios?

A

Production of too little amniotic fluid

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28
Q

What is oligohydramnios associated with? (2 things)

A
  1. Placental insufficiency
  2. Foetal renal impairments
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29
Q

What is polyhydramnios?

A

Production of too much amniotic fluid

30
Q

What is polyhydramnios associated with?

A

Foetal abnormalities (e.g inability to swallow)

31
Q

What are the important foetal CNS changes? (5 things)

A
  1. Corticospinal tracts (for voluntary movement) formed by month 4
  2. Brain myelination begins month 9
  3. Histological differentiation of cortex in cerebrum + cerebellum
  4. Formation + myelination of nuclei and tracts
  5. Growth of spinal cord + vertebral column
32
Q

When can a foetus begin to move?

A

Week 8

33
Q

What is quickening, and when does it develop?

A

Maternal awareness of foetal movements

Develops in week 17

34
Q

What is clinically important to check in the baby sensory + motor systems? (2 things)

A
  1. Viability: if brain mature enough to control body functions (e.g breathing)
  2. Sensory awareness: pain / sound
35
Q

What are the biggest factors affecting foetus viability? (2 things)

A
  1. Respiratory system
  2. CNS development
36
Q

How can foetal / neonate development be assessed? (4 things)

A
  1. Crown-Rump Length (CRL) (via US)
  2. Foot length (via US)
  3. Biparietal diameter of head
  4. Weight / appearance after delivering
37
Q

What are the effects of poor nutrition at Early pregnancy?

A

Symmetrical growth restriction (growth restriction is generalised and proportional)

38
Q

What are the effects of poor nutrition at Late pregnancy?

A

Asymmetrical growth restriction (abdominal growth lags, normal brain growth)

39
Q

What is poor nutrition of a foetus?

A

Deprivation of nutrional and oxygen supply to foetus

40
Q

What is the result of foetal pO2 being lower than adult pO2?

A

Foetal blood adapts to increase O2 content

41
Q

What are the adaptations of foetal blood? (3 things)

A
  1. Different Hb
  2. Higher Hb levels
  3. Efficient diffusion across placenta
42
Q

How does having different Hb help foetal blood have more oyxgen?

A

HbF has a higher affinity for O2 than Hb

  • HbF is made from 2 alpha + 2 gamma subunits (instead of 2 alpha + 2 beta)
  • No beta subunits → 2-3, DGP can’t bind → can’t reduce Hb affinity → affinity stays high
43
Q

How does having higher Hb levels help foetal blood have more oyxgen?

A

Carries more O2

44
Q

How is diffusion across the placenta efficient? (2 things)

A
  1. Low diffusion resistance
  2. High partial pressure gradient
45
Q

What is the relationship between a foetus and CO2?

A

Foetus can’t tolerate high CO2

Because it causes problems in acid-base balance

46
Q

What adaptations ensure foetal CO2 is kept low?

A

Progesterone → Maternal Hyperventilation → Maternal Hypocapnia → Creates pCO2 gradient between mother and foetus → constant placental transfer of CO2

47
Q

How is foetal circulation different from adult circulation? (3 things)

A
  1. Oxygenated blood enters circulation from placental transfer
  2. Pulmonary blood flow accounts for less than 20% of total CO (because high pulmonary vasculature resistance)
  3. 5 foetal vascular structures exists to direct blood flow
48
Q

What are the 5 foetal structures that direct the blood flow?

A
  1. Ductus Arteriosus
  2. Foramen ovale
  3. Ductus venosus
  4. Umbilical Arteries
  5. Umbilican Vein
49
Q

What does the Ductus Arteriosus do? (3 things)

A
  1. Connects Pulmonary Atery to Aorta
  2. Shunts blood R → L
  3. Diverts blood AWAY from lungs
50
Q

What does the Foramen Ovale do? (3 things)

A
  1. Connects 2 atria
  2. Shunts blood R → L
  3. Bypasses lungs
51
Q

What does the Ductus Venosus do? (3 things)

A
  1. Receives blood from umbilical vein
  2. Directs blood to IVC → R atrium
  3. Bypasses liver
52
Q

What do the Umbilical Arteries do?

A

Carry deoxygenated blood to placenta

53
Q

What does the Umbilical Vein do?

A

Carries oxygenated blood from placenta

54
Q

What are the requirements of foetal circulation and how are they met? (2 requirements)

A
  1. Higher pressure in R atria than L
    * so blood can flow R → L through Foramen Ovale
  2. Higher pressure in Pulmonary Artery than Aorta
    * so blood can flow correctly

Both requirements met in foetus because of high flow resistance of lungs

55
Q

What changes occur at birth to close the shunts?

A
  1. Ductus venosus closes as placenta is lost
  2. Foramen ovale closes when pressure in L atrium exceeds R atrium
    * First breath → Resistance in lungs decreases → vessels dilate → R atrium pressure decreases
  3. Ductus arteriosus contracts with increasing pO2 in aorta blood → subsequent contraction of SMC in its walls
56
Q

What is amniotic fluid?

A

Fluid surrounding foetus providing:

  • Mechanical protection
  • Moist environment → protects non K foetal skin
57
Q

What is the volume of amniotic fluid at:

  • 8 weeks
  • 38 weeks
  • 42 weeks
A

8 weeks: 10ml

38 weeks: 1L

42 weeks: 300ml

58
Q

What is the amniotic fluid derived from in early pregnancy? (2 things)

A
  1. Dialysis of foetal and maternal EC components
  2. Exchange across foetal skin (transudation)
59
Q

What are the cells in amniotic fluid derived from? (2 things)

A
  1. Amnion
  2. Foetus
60
Q

What is the amniotic fluid derived from in late pregnancy?

A

Mainly the foetus:

Foetal kidney produces hypotonic urine → forms major part of amniotic fluid

61
Q

What happens to the urine made by the foetal kidney in late pregnancy?

A

Swallowed by foetus in constant “cleaning system”

62
Q

What happens after the foetus swallows the urine?

A

The foetus absorbs the electrolytes and fluid in the gut

63
Q

What happens after the foetus absorbs the electrolytes and fluids from the urine in its gut?

A

Any “debris” remains and accumulates in the gut

This debris is called: Meconium

64
Q

What is Meconium?

A

Debris that remains in foetus gut after it has absorbed the fluid + electrolytes from swallowed urine

65
Q

When is Meconium excreted?

A

Only in distress

e.g foetal hypoxia

66
Q

What is amniotic fluid useful for?

A

Assessing foetal abnormalities

e.g neural tube defects / chromosomal abnormalities

Obtained and assessed by AMNIOCENTESIS

67
Q

When does foetal insuin begin to be secreted?

A

Week 10

68
Q

What creates the concentration gradient for glucose to enter the foetus?

A

High maternal glucose

69
Q

What does a foetus use glucose for?

A

Growth and development

70
Q

What happens to foetal bilirubin?

A

Can’t be excreted via gut → so passes across to maternal circulation

71
Q

Why is jaundice common in neonates?

A

Neonates can’t immediately deal with bilirubin