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Respiratory > Neonatal > Flashcards

Neonatal Flashcards

1
Q

From what part of the neonatal anatomy does the respiratory tract originate from?

A

Originate as an outpouching from the endodermal tube that gives rise to the GI tract

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2
Q

When is fetal development does alveolar formation begin?

A

Around 28 weeks gestation

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3
Q

True or false: Alveoli are fully formed at birth

A

false– will continue to develop for years

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4
Q

What is the stimulus for lung development in the fetus?

A

Lung fluid in the airway causes a distending force that stimulate growth

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5
Q

What is the effect of oligohydramnios on lung development? Why?

A

Decreases, since lung development relies on the pressure exerted from the lung fluid for expansion

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6
Q

What inhibits lung from becoming too large in fetal development?

A

External compression

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7
Q

What are the two major mechanisms that regulate lung development?

A
  • Physical factors

- Transcription factors/regulatory genes

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8
Q

What are the 5 phases of lung development?

A
  1. Embryonic
  2. Pseudoglandular
  3. Canalicular
  4. Saccular
  5. Alveolar
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9
Q

What is the order of airway development? (6)

A
  1. Bronchi
  2. Bronchioles
  3. Terminal bronchioles
  4. Respiratory bronchioles
  5. Alveolar ducts
  6. Alveolar sacs
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10
Q

What is occurring in the pseudoglandular phase of lung development? (3)

A

Formation of:

  • major airways
  • bronchial tree
  • portions of the respiratory parenchyma
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11
Q

What is occurring during the canalicular phase of prenatal lung development? (3)

A
  • Last generation of the lung periphery formed
  • Epithelial differentiation
  • Air-blood barrier formed
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12
Q

What are the two major events that occur in the saccular phase of lung development?

A
  • Expansion of air space

- Surfactant detectable in amniotic fluid

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13
Q

What is the major event that is occurring in the alveolar phase of lung development?

A

Secondary septation

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14
Q

When in gestation does surfactant develop?

A

Around week 24

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15
Q

When is the embryonic phase occurring in gestation (weeks gestation)?

A

0-8 weeks

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16
Q

When do the first segments appear in the five lobes of the lungs?

A

At the end of the embryonic phase

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17
Q

When have the pulmonary vessels formed in development?

A

End of the embryonic phase

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18
Q

What controls the first inward breathing movement at the end of the embryonic phase of development? What is different about this movement as compared to regular physiology?

A

A breathing center in the brain stem.

paradoxical movement, in that when the diaphragm contracts, the thorax moves inwardly and vv

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19
Q

When does the pseudoglandular phase take place in development?

A

8-17 weeks

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20
Q

What do the lungs look like in the pseudoglandular phase of development? What is significant about the end of this phase?

A

Resemble a gland

At the end of this phase, precursors of the pneumocytes can be discerned in the respiratory sections as cubic epithelium

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21
Q

When in development does the developing bronchopulmonary epithelium begin to develop amniotic fluid?

A

Pseudoglandular phase

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22
Q

When does the canalicular phase happen in development?

A

16-26 weeks

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23
Q

What happens to the pneumocytes in the canalicular phase of development?

A

Type I pneumocytes differentiate out of the type II

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24
Q

What happens to the capillaries in the canalicular phase of development?

A

Capillaries approach the walls of the acini

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25
Q

What is the chief characteristic change that occurs during the canalicular phase of development?

A

Alteration of the epithelium and the surrounding mesenchymal

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26
Q

During what stage of development does the lung epithelium begin to produce a large portion of the amniotic fluid?

A

Canalicular phase

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27
Q

When can the maturity of the lungs begin to be measured clinically? What is measured for this?

A

Canalicular phase–based on the activity of the type II cells to produce surfactant

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28
Q

Damage during the canalicular phase of development will produce what complication?

A

Damage will affect the gas-exchange components and result in structural alterations of the later pulmonary parenchyma

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29
Q

When in development does the saccular phase occur?

A

24-38 weeks

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30
Q

What are the major morphological changes that occur during the saccular phase of lung development?

A

Whole clusters of sacs form on the terminal bronchi, which represent the last subdivision of the passages that supply air

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31
Q

What forms at the end of each respiratory tract in the saccular phase?

A

Smooth walled sacculi form, coated with Type I and II pneumocytes

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32
Q

What are the characteristics of the septa in the saccular phase of development?

A

Septa contain two networks of capillaries coming from neighboring sacculi

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33
Q

What occurs with the intraductal space and intersaccular space during the saccular phase of development?

A

Fibroblasts begin to produce extracellular material in the interductal and intersaccular space

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34
Q

At the end of the which phase of lung development, have all generations of the conducting and respiratory branches been generated?

A

Saccular

35
Q

What organelle produces surfactant? How is this pacakged to leave the cell?

A

rER produces it, and packages it into lamellar bodies

36
Q

What cells produce surfactant?

A

Type II pneumocytes

37
Q

What is the major histological evidence that identifies mature type II pneumocytes?

A

Lamellar bodies

38
Q

IN the alveolar lumen, the lamellar bodies unravel to form what?

A

Tubular myelin and ultimately surfactatns

39
Q

What are the main components of surfactant?

A

Phosphatidylcholine (lecithin 75%)

40
Q

What is the best measure of fetal lung maturity? When does this increase?

A

Ratio of levithin/sphingomyelin concentrations in the amniotic fluid

Increases from the 32nd weeks of gestation

41
Q

What ratio of lecithin/sphinomyelin is concerning for the development of IFDS?

A

1.5 or below

42
Q

What is the function of SP-A (surfactant-specific protein)?

A

Immune defense function

43
Q

What is the function of SP-D (surfactant-specific protein)?

A

Immune defense function

44
Q

What is the function of SP-B (surfactant-specific protein)?

A

Critical for surface activity

45
Q

What is the function of SP-c (surfactant-specific protein)?

A

Critical for surface activity

46
Q

What is the major componet of surfactant that is missing from commercial preparations of surfactant?

A

SP-A and D

47
Q

What are the stimulants of surfactant synthesis?

A

Glucocorticoids
Thyroid hormones
cAMP
Epidermal growth factors

48
Q

What are the two agonists that stimulate surfactant synthesis?

A

Beta adreergic

Purinoceptors (adenosine)

49
Q

What maternal disease inhibits the development of surfactant?

A

DM

50
Q

What is the effect of a maternal overproduction of thyroid hormone on lung function?

A

Overbranching of the lungs

51
Q

What will stimulate cAMP in respiration?

A

Xanthine

52
Q

What is the beta agonist that will stimulate surfactant synthesis?

A

Terbutaline

53
Q

When in gestation does the alveolar phase take plase?

A

36-2 weeks postpartum

54
Q

What fraction of the adult count of 300 million alveoli are formed at birth?

A

1/3

55
Q

What happens in the alveolar phase?

A

Alveoli form from the terminal endings of the alveolar sacculi, and increase in diameter

56
Q

During the alveolar phase, the alveoli are only present in their beginning form. What lies between them that is not present in their fully mature form?

A

Between them lies the parenchyma, composed of a double layer of capillaries that forms the primary septa between the alveolar sacculi

57
Q

What are the three main processes that occur during lung development in late fetal life?

A
  • Increase in the number and size of the alveoli
  • Thinning of the CT septa between alveoli
  • Alveolar lining cells become flatter
58
Q

What is the purpose of the thinning of the septa between alveoli during the alveolar phase?

A

Reduce distance between the alveoli and capillaries, facilitating gas exchange

59
Q

What is the relative lung compliance in the full term, intrauterine lung? Chest compliance?

A

Low lung compliance

High chest compliance

60
Q

What are the breathing movements like in the full term intrauterine lung?

A

30% of the lungs have shallow breathing movements

61
Q

Are the vessels in the full term uterine lung dilated or constricted?

A

Constricted

62
Q

What are the four major changes the must occur rapidly and concurrently following birth?

A
  • Continuous breathing and ventilation must start
  • Functional residual capacity must be established
  • Pulmonary vasculature must dilate
  • Fetal pulmonary fluid must be absorbed
63
Q

What are the chemical stimuli that start the breathing process at birth?

A

Increased pCO2

Decrease pO2

64
Q

What are the environmental stimuli that occur at the onset of breathing?

A

Cooling
Light
Sound
Pressure

65
Q

Is the first breath forceful or weak?

A

Forceful

66
Q

Is expiration of the first breath active or passive?

A

Active

67
Q

What process allows the air passage to open?

A

Transpulmonary pressure increases with the adduction of the vocal cords, to establish residual capacity

68
Q

What happens to the capillaries with the first breath?

A

Recruitment and distension of the newly oxygenated capillaries

69
Q

The process of opening alveoli is dependent on what major factor? Why?

A

Surfactant, which lowers lung surface tension

70
Q

Initially, there is a high respiratory rate with the first breath. What brings this down?

A

J receptors are activated by interstitial pressure creased by fetal lung fluid

71
Q

What hormone surge allows for the resorption of fetal lung fluid? How does this work? What enhances this initial absorption?

A

NE–stimulates transepithelial Na transport to pull Na and water into the capillaries

Thyroid and steroid hormones, as well as alveolar-capillary pressure gradient increase this

72
Q

What causes the paradoxical breathing pattern of infants?

A

Highly compliant chest wall, with low lung compliance

73
Q

What causes the low dynamic lung compliance after birth?

A
  • Viscous properties of lung tissue

- Distortion of the pliable chest

74
Q

How do the resistances of the nasal and oral airways compare in infants and adults?

A

Lower nasal airway resistance in infants compared to oral. vv for adults

75
Q

True or false: there is a large change in the compliance of the lungs and chest within the first few minutes of life

A

True

76
Q

Why are the newborn’s respiratory mechanics not very efficient?

A

Chest distortion

Round skeletal contour (not optimal resting length for diaphragm and intercostals)

77
Q

What are the characteristics of the respiratory muscles initially after birth?

A

Small mass

Few fatigue resistance, slow twitch

78
Q

What are the three main causes of the in-homogeneous air distribution in the neonatal lungs?

A
  • Pliant airway
  • Chest wall distortion
  • Immature respiratory muscles
79
Q

What happens to the pulmonary circulation after birth?

A
  • Decreased pulmonary arteries:alveoli ratio,

- there is less vascular resistance

80
Q

How does the breathing pattern change as the neonate matures?

A

Changes from episodic to continuous

81
Q

Short period of apnea are normal in infants. How can you tell if this is an issue?

A

Arousal of the infant

82
Q

Periodic breathing and apnea usually occur when in the neonates early life?

A

During sleep

83
Q

Why is hypoxia early in fetal life bad?

A

Increase***

Respiratory (34 decks)

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