Developmental Aspects of Lung Disease

Question 1

What are the stages of lung morphogenesis?

Answer 1

Embryonic - 3-8 weeks Pseudo-glandular - 5-17 Canalicular - 16 - 26 Saccular - 24 - 38 Alveolar - 36 weeks (2 to 3 years)

Question 2

What happens during the embryonic and pseudoglandular stages of lung development?

Answer 2

Formation of Major Airways Formation of Bronchal tree and portions of respiratory parenchyma

Birth of the acinus

Embryonic: appearance of lung buds and main pulmonary arteries

Pseudoglandular: All conducting airways and accompanying blood vessels form

Question 3

What is meant by respiratory parenchyma?

Answer 3

Pulmonary parenchyma is a term for lung tissue, including bronchioles, interstitium and alveoli

Question 4

What happens during the canalicular stage of lung development?

Answer 4

Last generations of the lung periphery formed

Epithelial differentiation - acinai are replacing columnar epithelium with squamous epithelium

Air-blood barrier formed

Question 5

What is significant about the canaliculi stage?

Answer 5

Life outside of the uterus is possible after the canalicular stage

Question 6

What happens during the saccular stage?

Answer 6

Expansion of air spaces

Surfactant detectable in amnionic fluid

Question 7

What happens during the alveolar stage?

Answer 7

Secondary septation

Question 9

Which stages are organogenesis

Which are differentiation?

Answer 9

Organogenesis (embryonic and pseudoglandular)

Differentiation (cannalicular and saccular)

Question 10

What types of congenital lung disease exist which arise in the embryonic stage?

Answer 10

Tracheal, laryngeal stenosis (laryngeal stenosis is the narrowing of the airway that may affect the supraglottis, glottis, and/or subglottis)

Pulmonary agenesis (lungs not forming)

Tracheo-oesophageal fistula (abnormal connection between the oesophagus and the trachea)

Question 11

What congenital lung diseases arise from the pseudoglandular stage of lung development?

Answer 11

Pulmonary sequestration - congenital malformation of the lower respiratory tract. It consists of a nonfunctioning mass of normal lung tissue that lacks normal communication with the tracheobronchial tree, and that receives its arterial blood supply from the systemic circulation.

Cystadenomatoid malformation - one of the lobes containing a group of fluid or air-filled spaces (cysts), rather than lung tissue.

Cyst formation

Question 12

How long does it take the diaphragm to close?

Answer 12

18 weeks

Question 13

How is the diaphragm formed?

Answer 13

Various sheets of primitive tissue move towards the centre of the diaphragm.

Question 14

What are the outcomes of diaphragmatic hernia?

Answer 14

Pulmonary hypoplasia

Persistant pulmonary hypertension

Question 15

What is meant by diaphragmatic eventration?

Answer 15

Abnormal displacement (i.e. elevation) of part or all of an otherwise intact diaphragm into the chest cavity.

Question 16

What are the functional changes in the lung at birth?

Answer 16

Change from fluid secretion to fluid absorption

Pulmonary vasodilation

Question 17

What is Transient tachypnea of the Newborn?

Answer 17

Transient tachypnea of the newborn is a respiratory problem that can be seen in the newborn shortly after delivery. … It consists of a period of rapid breathing (higher than the normal range of 30-60 times per minute). It is likely due to retained lung fluid.

Question 18

What are the components of surfactant?

Answer 18

Phospholipids and lipophilic components

Stabilises alveoli and promotes gas exchange

Question 19

When do surfactant proteins appear?

Answer 19

12-14 weeks

Question 20

What does surfactant deficiency cause?

Answer 20

Hyaline Membrane Disease A syndrome in prematureinfants caused by developmental insufficiency of pulmonary surfactant production and structural immaturity in the lungs. It can also be a consequence of neonatal infection. It can also result from a genetic problem with the production of surfactant associated proteins.

Question 21

What is chronic neonatal lung disease?

Answer 21

Results from the effects of positive pressure ventilation on a structurally and functionally immature lung

CLD is characterised primarily by prolonged need for ventilatory support, O2 requirements, need for home oxygen and readmission with respiratory illness in the first year of life.

Bronchopulmonary dysplasia is used interchangeably with CLD.

Condition causes eventual lung fibrosis and emphysematous changes

Question 22

What are the antenatal fetal / paediatric origins of adult lung disease?

Answer 22

In utero nicotine exposure - passes across placenta and reduces airway diameter in the child.

Nutrition

Low birth weight/prematurity (antenatal steroids) – reduces total number of alveoli?

Micronutrients and vitamins

Question 23

What are the post-natal fetal/paediatric origins of lung disease?

Answer 23

Infection

Growth

Environmental tobacco smoke

Environmental Pollution

Micronutrients/vitamins

Question 24

Influences on Lung development

Answer 24

Accelerated decline

Early decline

Failure to attain maximal growth

Abnormal decline

Question 25

What does neonatal lung disease cause?

Answer 25

Increased severity bronchiolitis

“asthma”

? future COPD

Question 26

What is the treatment for hyaline membrane disease?

Answer 26

Antenatal glucocorticoids

Surfactant replacement

Oxygen

CPAP

Mechanical ventilation