Prematurity and pre-natal medicine

Question 1

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

Answer 1

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

Question 2

When is the pseudoglandular period?

Answer 2

6 - 16 weeks

Question 3

What occurs during the pseudoglandular period?

Answer 3

14 generations of branching terminal bronchioles formed

NO respiratory bronchioles

Co-branching of pulmonary arteries

Question 4

When is the canilicular period?

Answer 4

16 - 26 weeks

Question 5

What occurs during the canilicular period?

Answer 5

1. Terminal bronchioles divide into respiratory bronchioles

2. Alveolar ducts

Question 6

When is the saccular period?

Answer 6

28 - 36 weeks

Question 7

What occurs during the saccular period?

Answer 7

1. Terminal sacs form

2. Capillaries in close contact with primitive alveoli

Question 8

What do the terminal sacs give rise to?

Answer 8

Alveoli

Question 9

When is the alveolar period?

Answer 9

8 months to childhood

Question 10

What occurs during the alveolar period?

Answer 10

Maturation of alveoli

Question 11

How many terminal sacs are there at birth?

Answer 11

20-70 million

Question 12

How long does terminal sac formation continue for?

Answer 12

Until about 8 years old

Question 13

How many terminal sacs are there in the mature lung?

Answer 13

300-400 million

Question 14

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

Answer 14

Sac lining cells (type I pneumocytes) are thinner

Capillaries protrude into alveolar sacs

Increasing contact points for gas exchange

Question 15

When does surfactant start being produced?

Answer 15

End of 6th month when type II pneumocytes appaer

Question 16

What is surfactant?

Answer 16

Saturated and unsaturated phospholipids, proteins and carbohydrates

Reduces surface tension

Continuous synthesis, secretion and re-uptake cycle

Question 17

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

Answer 17

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

Question 18

What are the effects of prematurity on lung function?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

How is RDS diagnosed?

Answer 20

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

Question 21

How is RDS treated?

Answer 21

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

Question 22

When can primitive gas exchange start?

Answer 22

22 - 24 weeks

Question 23

What developmental problems may develop in the embryonic period?

Answer 23

1. Agenesis/aplasia
2. Tracheal stenosis
3. Congenital cysts

Question 24

What developmental problems may develop in the pseudoglandular period?

Answer 24

1. Diaphragmatic hernia

2. Hypoplasia following amniocentesis

Question 25

What developmental problems may develop in the canilicular period?

Answer 25

1. Hypoplasia

2. Potter’s

Question 26

What is the liquid in the lungs?

Answer 26

NOT aspirated amniotic fluid or plasma

Actively secreted by the lungs

Question 27

What promotes clearance of liquid in the lungs at birth?

Answer 27

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

Question 28

When does lung liquid start to clear?

Answer 28

2-3 days before term delivery