Developmental Aspects of Lung Disease

Question 1

What are the five stages of the embryological development of the lungs?

Answer 1

1. Embyronic (3-8 weeks)
2. Pseudoglandular (5-17 weeks)
3. Canalicular (16-26 weeks)
4. Saccular (24-38 weeks)
5. Alveolar (36 weeks - 2/3 years)

Question 2

What occurs in the embyronic phase of lung development?

Answer 2

Laryngeal tracheal groove comes off primitive foregut and grows into surrounding mesoderm
Later divides to form 2 lung buds
Eventually these branch out form Bvs
Filled with fluid

Question 3

What occurs in the pseudoglandular phase of lung development?

Answer 3

Moving and budding out to form primitive lung with a few branches
Tracheal cartilage begins to form
Lobe formation
Primitive airway with columnar epithelium
Starting to get myofibroblasts around outside
Branching off into primitive tubules
BVs still too far away from tubules for exchange

Question 4

What occurs in the canalicular phase of lung development?

Answer 4

More branches form
Primitive sacs
Acini filling so forming more squamous rather than cuboidal epithelium
Capillaries close enough for gas exchange

Question 5

What occurs in the saccular phase of lung development?

Answer 5

More and more saccules form

More acini form and bud off to become alveoli

Question 6

What occurs in the aveolar phase of lung development?

Answer 6

Thin walled sacs with few cells bud off resp tract

Question 7

What is tracheal/laryngeal stenosis?

Answer 7

Narrowing of lumen due to failure to recanalise

Question 8

What is pulmonary agenesis?

Answer 8

Failure of development of 1 lung bud = only 1 lung

Question 9

What is pulmonary sequestration?

Answer 9

Piece of tissue develops into lung but is not attached to pulmonary arterial blood supply and so does not contribute to respiration

Question 10

What are the two types of pulmonary sequestration?

Answer 10

Extralobar - extra lung that has its own pleural sac

Intralobar - usually within visceral pleura of normal lung tissue

Question 11

What is cystadenomastoid malformation?

Answer 11

Malformation of the airways, some associated with cystic areas and adenomatous overgrowth of terminal bronchioles

Question 12

On what side is diaphragmatic hernia most common?

Answer 12

L (liver plugs on R side)

Question 13

What is congenital diaphragmatic hernia?

Answer 13

Herniation of abdominal viscera into the chest cavity due to incomplete formation of the diaphragm

Question 14

What can congenital diaphragmatic hernia lead to?

Answer 14

Pulmonary hypoplasia (incomplete lung development) and HTN –> respiratory distress shortly after birth

Question 15

What is the pathophysiology of congenital diaphragmatic hernia?

Answer 15

Failure of pleuroperitoneal canal to close completely

Question 16

What is eventration of the diaphragm?

Answer 16

Abnormal elevation of part/all of an otherwise normal diaphragm into the chest cavity

Question 17

What functional changes occur in the lungs at birth?

Answer 17

Fluid secretion –> fluid absorption

Pulmonary vasodilation to allow gas exchange

Question 18

What is the commonest cause of respiratory distress in the newborn period?

Answer 18

Transient tachypnoea of the newborn

Question 19

What causes TTN?

Answer 19

Delayed resorption of fluid in the lungs

Question 20

What is a RF for TTN?

Answer 20

C-section (as fluid is not squeezed out during passage through birth canal)
Prematurity

Question 21

What might CXR should in TTN?

Answer 21

Hyperinflation, fluid in horizontal fissure

Question 22

What is the treatment of TTN?

Answer 22

Supplementary oxygen

Usually settles within 1-2 days

Question 23

What cells make surfactant?

Answer 23

Type II pneumocytes

Question 24

What is surfactant deficient lung disease?

Answer 24

AKA RDS and hyaline membrane disease
Condition seen in premature babies due to insufficient surfactant and structural immaturity of the lungs (smaller alveoli collapse into bigger ones)

Question 25

Aside from prematurity what are other RFs for surfactant deficient lung disease?

Answer 25

Male
Diabetic mother
C-section
2nd born of premature twins

Question 26

What are clinical features of surfactant deficient lung disease?

Answer 26

Tachypnoea, intercostal recession, expiratory grunting and cyanosis

Question 27

What is the typical CXR finding with surfactant deficient lung disease?

Answer 27

Ground glass appearance with an indistinct heart border

Question 28

What is the management of surfactant deficient lung disease?

Answer 28

Prevent with corticosteroids during pregnancy to induce foetal lung maturity
Oxygen
Assisted ventilation (e.g. CPAP)
Exogenous surfactant given via endotracheal tube