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human development > fetus to neonate > Flashcards

fetus to neonate Flashcards

1
Q

describe the in-utero environment

A
  • Foetus surrounded by amniotic fluid
  • Warm, cushioned, quiet
  • Fluid filled lungs
  • Foetal circulation
  • Relative hypoxia – O2 and CO2 exchange via placenta
  • Nutrient acquisition and waste elimination via placenta
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2
Q

what mediates the filling of the lungs with fluid before birth?

A

active chloride secretion

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3
Q

when does surfactant secretion start?

A

24 weeks gestation

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4
Q

what increases surfactant secretion?

A

glucocorticoids

thyroid hormones

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5
Q

when does the foetus make breathing efforts before birth?

A

during sleep

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6
Q

describe the gasping reflex?

A

will gasp if O2 supply is removed

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7
Q

describe what pulmonary changes happen at birth?

A
  • physical pressure of labour squeezes some of the fluid out
  • initial breath causes -ve thoracic pressure –> opens the airways
  • active absorption of alveolar fluid via Na+ transport
  • Establishes a functional residual volume
  • Onset of regular respirations
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8
Q

how does active absorption of alveolar fluid occur?

A

via sodium transport stimulated by cortisol, catecholamines and thyroid hormones

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9
Q

what forms surfactants?

A

type II pneumocytes in the alveoli

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10
Q

what is surfactant?

A

lipoprotein complex consisting of;

  • phospholipids
  • surfactant proteins A, B, C and D
  • other lipids e.g. cholesterol and trace substances
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11
Q

what are the lipoproteins and what are their functions?

A

B + C = structural

A + D = immune

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12
Q

what is the function of surfactant and how does the occur?

A

it reduces surface tension by:
o Increasing pulmonary compliance
o Preventing atelectasis

also has some innate immunity function

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13
Q

what is atelectasis?

A

collapse/closure of the lung, resulting in reduced/absent gas exchange

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14
Q

where does most oxygenated blood in a fetus come from?

A

placenta

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15
Q

where does most oxygenated blood in the fetus go?

A

heart and brain

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16
Q

what changes happen to the cardiovascular system at birth?

A
  • Blood flow in umbilical vessels ceases –> systemic vascular resistance rises
  • Increase in pulmonary blood flow –> pulmonary vascular resistance drops
  • RA pressure drops, LA pressure rises, reducing flow through foramen ovale
  • Flow preferentially goes to RV and pulmonary artery
  • Flow through ductus arteriosus changes
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17
Q

what cardiovascular follow on changes happen?

A
  • ductus arteriosus closes functionally and anatomically
  • foramen ovale functionally closes soon after birth
  • umbilical vein forms the round ligament of the liver
  • umbilical artery partly obliterates to become the medial umbilical ligament
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18
Q

what causes the closure of the ductus arteriosus?

A

increasing pO2 and decreased prostaglandins

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19
Q

why cant pregnant mothers have ibuprofen

A

contains prostaglandins –> causes ductus arteriosus to close

20
Q

when does the ductus arteriosus close functionally?

A

12-15 hours after birth

21
Q

when does the ductus arteriosus close anatomically?

A

4-6 days anatomically

22
Q

how does the ductus arteriosus change anatomically?

A

forms ligamentum arteriosum

23
Q

how does the umbilical artery change after birth?

A

o Partly obliterates to become the medial umbilical ligament

o A part remains open as a branch of the anterior division of the internal iliac artery

24
Q

what happens to foetal cortisol levels during the third trimester?

A

increase

25
Q

what does an increase in cortisol levels do?

A

o Stimulates surfactant production
o Activates thyroid hormone
o Matures hepatic glucose and gut digestive enzymes
o Increase in beta-adrenergic receptors

26
Q

what does the surge of catecholamines during delivery do?

A

o Raises blood pressure
o Supports energy metabolism
o Aids thermogenesis via brown fat - releasing energy as heat rather than ATP (important to combine with skin-to-skin)

27
Q

describe the metabolism of the new baby?

A

• Nutritional supply from placenta stops at birth and blood glucose levels fall
• Reduction in insulin, rise in glucagon and catecholamines
- lower blood glucose
- glucose –> fatty acids and ketone bodies
- increase in intestinal motility

28
Q

what energy supply to newborns use in utero?

A

glucose

29
Q

what energy supply do newborns use after birth?

A

fatty acids and ketone bodies

30
Q

what is the initial feeding supply of a child?

A

colostrum, the energy rich first milk

31
Q

what is meconium?

A

dark green first faeces of an infant

32
Q

when should the passage of meconium be?

A

within the first 48 hours

33
Q

how does the fetus overcome the low oxygen levels in utero?

A
  • Foetus and neonate have higher red blood cell levels

- Foetal haemoglobin has higher affinity for O2

34
Q

where does haemopoiesis transition from after birth?

A

liver to bone marrow

35
Q

why is clotting variable in babies/

A

clotting factors dont cross the placenta so neonates have a lower value than adults

36
Q

what vitamin are neonates deficient in?

A

Vitamin K

37
Q

why is neonatal jaundice common?

A
  • Breakdown of foetal red cells results in high levels of bilirubin
  • Poor activity of hepatic glucuronyl transferase leads low levels of conjugation and biliary excretion
38
Q

when is urine produced in a fetus?

A

16 weeks of gestation

39
Q

when does nephrogenesis finish?

A

34 weeks

40
Q

what does an increase in renal blood flow lead to?

A

increase in GFR

41
Q

when should babies pass their first urine?

A

first 24 hours

42
Q

when does diuresis establish?

A

within the first few days, with increase in urine output and loss of water

43
Q

why is it okay that the fetus is immunosuppressed in utero?

A

sterile environment

44
Q

what does immunity rely on postnatally?

A

o innate immune system - although has less capability to mount neutrophil response
o maternally-derived IgG
- gains immune benefit from breastmilk - IgA, complement, lactoferrin, lysozyme

45
Q

name causes of difficult transition?

A

o Prematurity
o Other disease states in baby, e.g. congenital abnormalities, infection, asphyxia
o Non-labour deliveries, e.g. elective caesareans
o Complicated deliveries
o Maternal health and medications (including anaesthesia)

human development (20 decks)

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