Developmental Aspects of Lung Disease

Question 1

What are the 5 stages in lung morphogenesis?

Answer 1

1. embryonic
2. pseudo-glandular
3. canalicular
4. saccular
5. alveolar

Question 2

When is extra-uterine life possible?

i.e. premature babies

Answer 2

at late canalicular/early saccular stage (22-24 weeks)

Question 3

What happens in the embryonic stage of lung morphogenesis?

Answer 3

• The respiratory diverticulum buds off the duodenum structure.
• Cells of trachea are cuboidal.
• Appearance of lung buds, main pulmonary arteries, trachea and main bronchi.

Question 4

What happens in the pseudoglandular stage of lung morphogenesis?

Answer 4

• all conducting airways and accompanying vessels form.

- wall structure and epithelial cells differentiate.

Question 5

What is the canalicular stage of lung morphogenesis?

Answer 5

• Respiratory airways form.
• Blood-gas barrier thins
• surfactant appears

Question 6

What is the saccular stage of lung development?

Answer 6

• saccules and then alveoli appear.
• air spaces expand
• surfactant detectable in amniotic fluid

Question 7

What is the alveolar stage of lung morphogenesis?

Answer 7

• Secondary septation of alveoli which begins in utero, but continues after birth.
• alveoli multiply for 2-4 years.

Question 8

What stages of morphogenesis are the conducting zones developed?

What are these?

Answer 8

embryonic and psuedoglandular

bronchi, bronchioles and terminal bronchioles

Question 9

Outline four upper congenital respiratory abnormalities.

Answer 9

• tracheal agenesis
• tracheal stenosis
• tracheomalacia
• tracheo-oesophagul fistula

Question 10

Outline four upper congenital respiratory abnormalities.

Answer 10

- Lung agenesis/
Pulmonary Hypoplasia
- Bronchogenic cyst
- CPAM
- Congenital Diaphragmatic Hernia

Question 11

What is tracheal stenosis?

When is it likely to develop?

Answer 11

• Complete tracheal cartilage rings, may be generalized or segmental, causes narrowing of trachea.
• the rings harden to early and cause blockages.

Originates in the earlier stages of lung morphogenesis

Question 12

What is tracheomalacia and in what stage of lung development is it likely to originate from?

Answer 12

• trachea and bronchi are floppy due to softening

- originates in earlier stages of lung morphogenesis

Question 13

What does tracheomalacia present with? (4)

Answer 13

• Barking cough
• Recurrent “croup” infection
• Breathless on exertion
• Stridor/wheeze – sucking in sound, whistling wheeze

Question 14

How does tracheomalacia develop over time?

How is it treated?

What can worsen the situation?

Answer 14

Treated with physiotherapy and antibiotics.

Tracheal rings strengthen over time with growth.

Salbutamol

Question 15

What is tracheo-oesphageal fistula?

Answer 15

Abnormal connection between trachea and oesphagus.

Question 16

What does tracheo-oesphageal fistula present with?

How is it treated?

Answer 16

• Choking
• Colour change
• Cough with feeding
• Unable to pass NG

Surgery

Question 17

What is CPAM?

Answer 17

Congenital Pulmonary Airway Malformation

• a rare congenital birth defect that includes a cystic mass of abnormal lung tissue.

Question 18

What is pulmonary agenesis/hypoplasia and in what stage of lung development is it likely to originate from?

(2)

Answer 18

• Incomplete development of the lungs, resulting in an abnormally low number or size of bronchopulmonary segments or alveoli.
• originates in earlier stages of lung morphogenesis.

Question 19

How does the diaphragm develop?

Answer 19

Membranes develop towards the centre of the embryo until the fuse in the centre.

Question 20

What may happen if the diaphragm doesn’t develop correctly?

Answer 20

Congenital Diaphragmatic Hernia

Question 21

What can a congenital diaphragmatic hernia result in?

2

Answer 21

• pulmonary hypertension

- pulmonary hypoplasia

Question 22

What is transient tachypnoea of the newborn?

When might it occur?

Answer 22

• amnionic fluid remains in the lung after birth, resolves in 24-48hrs
• C-section: lungs not squeezed as they come out birth canal.

Question 23

What is a surfactant deficiency called?

Answer 23

IFDS (Infant Respiratory Distress Syndrome)

Question 24

What is the treatment for IRDS, both pre- and antenatal?

3

Answer 24

• Antenatal steroids (if going into early labor)
• Surfactant replacement
• Appropriate ventilation and nutrition

Question 25

Chronic Lung Disease associated with _________ where ongoing _______ requirement at term.

Also called _________ __________.

Answer 25

prematurity
oxygen

bronchopulmonary dysplasia

Question 26

What are the antenatal causes of adult lung disease (COPD)?

6

Answer 26

• Nicotine exposure
• Infection
• Maternal nutrition
• Maternal micronutrients/vitamins
• Low birth weight/prematurity
• Antenatal steroids - IRDS

Question 27

What are the post-natal causes of adult lung disease?

6

Answer 27

• Barker hypothesis
• Recurrent infection
• Growth – underweight/overweight
• Tobacco exposure
• Environmental pollution
• Micronutrients/vitamins

Question 28

What is remodelling?

What leads to remodelling? (3)

Answer 28

Alteration of airway structure following external influence.

• Environmental exposures
• Chronic diseases of childhood
• Infection

Question 29

Name a childhood lung condition which may lead to remodelling?

Answer 29

bronchial asthma

Question 30

What are causes of chronic neonatal lung disease?

3

Answer 30

• Chronic inflammation
• Interference inter-cellular signalling
• Treatment toxicity e.g. O2