Prematurity and pre-natal medicine Flashcards Preview

Human Reproduction > Prematurity and pre-natal medicine > Flashcards

Flashcards in Prematurity and pre-natal medicine Deck (28)
Loading flashcards...
1
Q

How much of the respiratory system has developed by weeks 5-6 of gestation?

A
  1. Mainstem bronchi
  2. Secondary bronchi
  3. Development of caudal growth
  4. Tertiary bronchi
2
Q

When is the pseudoglandular period?

A

6 - 16 weeks

3
Q

What occurs during the pseudoglandular period?

A

14 generations of branching terminal bronchioles formed

NO respiratory bronchioles

Co-branching of pulmonary arteries

4
Q

When is the canilicular period?

A

16 - 26 weeks

5
Q

What occurs during the canilicular period?

A
  1. Terminal bronchioles divide into respiratory bronchioles

2. Alveolar ducts

6
Q

When is the saccular period?

A

28 - 36 weeks

7
Q

What occurs during the saccular period?

A
  1. Terminal sacs form

2. Capillaries in close contact with primitive alveoli

8
Q

What do the terminal sacs give rise to?

A

Alveoli

9
Q

When is the alveolar period?

A

8 months to childhood

10
Q

What occurs during the alveolar period?

A

Maturation of alveoli

11
Q

How many terminal sacs are there at birth?

A

20-70 million

12
Q

How long does terminal sac formation continue for?

A

Until about 8 years old

13
Q

How many terminal sacs are there in the mature lung?

A

300-400 million

14
Q

How does the blood-air barrier change at 8-9 months?

A

Sac lining cells (type I pneumocytes) are thinner

Capillaries protrude into alveolar sacs

Increasing contact points for gas exchange

15
Q

When does surfactant start being produced?

A

End of 6th month when type II pneumocytes appaer

16
Q

What is surfactant?

A

Saturated and unsaturated phospholipids, proteins and carbohydrates

Reduces surface tension

Continuous synthesis, secretion and re-uptake cycle

17
Q

What causes the fall in pulmonary vascular resistance at term birth?

A
  1. Lung distension
  2. Alveolar oxygen tension
  3. Nitric oxides
  4. Prostacyclins
  5. Endothelins
18
Q

What are the effects of prematurity on lung function?

A
  1. Small lungs
  2. Reduced number of alveoli, which are immature
  3. Reduced epithelial-endothelial contact
  4. Deficient surfactant
  5. Retained lung fluid
19
Q

What signs might you see in an infant with respiratory distress syndrome?

A
  1. Tachypnoea
  2. Dyspnoea
  3. Grunting
  4. Nasal flaring
  5. Subcostal recession
  6. Cyanosis
  7. Tachycardia
  8. Inability to feed
20
Q

How is RDS diagnosed?

A
  1. History
  2. Examination
  3. Chest x-ray
  4. Blood gas analysis
21
Q

How is RDS treated?

A
  1. Prenatal steroids to stimulate lung maturation in women at risk of having preterm birth
  2. Postnatal surfactant
22
Q

When can primitive gas exchange start?

A

22 - 24 weeks

23
Q

What developmental problems may develop in the embryonic period?

A
  1. Agenesis/aplasia
  2. Tracheal stenosis
  3. Congenital cysts
24
Q

What developmental problems may develop in the pseudoglandular period?

A
  1. Diaphragmatic hernia

2. Hypoplasia following amniocentesis

25
Q

What developmental problems may develop in the canilicular period?

A
  1. Hypoplasia

2. Potter’s

26
Q

What is the liquid in the lungs?

A

NOT aspirated amniotic fluid or plasma

Actively secreted by the lungs

27
Q

What promotes clearance of liquid in the lungs at birth?

A
  1. Active sodium reabsorption
  2. Lymphatic drainage
  3. Pulmonary blood vessels
  4. Squeezed out during birth
28
Q

When does lung liquid start to clear?

A

2-3 days before term delivery