First breath

Question 1

Embryonic (0-5 weeks)

Answer 1

Foregut derivative.
Anterior outpouching.
An oesophageal appendix.
By the 5th week the lung buds enlarge to form right and left main bronchi.

Question 2

Pseudoglandular (5-17 weeks)

Answer 2

Exocrine gland only
Major structural units formed
Angiogenesis
Mucous Glands
Cartilage
Smooth Muscle
Cilia
Lung fluid

Question 3

Cannalicular (16 - 25 weeks)

Answer 3

Distal Architecture
Vascularisation; i.e. formation of capillary bed
Respiratory bronchioles
Alveolar ducts
Terminal sacs

Question 4

Alveolar 25 weeks – term

Answer 4

Alveolar sacs
Type 1 and Type 2 cells
Alveoli simple with thick interstitium

Birth to 3-5 years?
Thinning of alveolar membrane and interstitium
↑ complexity of alveoli

Question 5

Stages of Lung Development

Answer 5

5-17 weeks = Major airways defined, Nests of angiogenesis, Smaller airways down to respiratory bronchioles.
16-25 weeks = Terminal bronchioles, Capillary Beds, Alveolar ducts.
24-40 weeks = Alveolar budding, thinning and complexification.

Question 6

Things that can go wrong - embryonic

Answer 6

Laryngeal, tracheal and oesophageal atresia, tracheal and bronchial stenosis, pulmonary agenesis (one lung not developing).

Question 7

Things that can go wrong - pseudoglandular

Answer 7

Bronchopulmonary sequestration, cystic adenomatoid malformations, alveolar-capillary dysplasia.

Question 8

Things that can go wrong - alveolar

Answer 8

Acinar dysplasia, alveolar capillary dysplasia, pulmonary hypoplasia, respiratory disease of the newborn.

Question 9

Foetal airways

Answer 9

Distended with fluid - Fluid aids in lung development - Actively secreted by lungs.

Question 10

Ductus Arteriosus

Answer 10

Pulmonary trunk linked to the distal arch of aorta by the ductus arteriosus, permitting blood to bypass pulmonary circulation.
Muscular wall contracts to close after birth (a process mediated by bradykinin)

Question 11

Ductus venosus

Answer 11

Oxygenated blood entering the foetus also needs to bypass the primitive liver. This is achieved by passage through the ductus venosus, which is estimated to shunt around 30% of umbilical blood directly to the inferior vena cava.

Question 12

Foramen Ovale

Answer 12

A passage between the two atria, which is responsible for bypassing the majority of the circulation.

Question 13

Adaptive changes at birth

Answer 13

Fluid squeezed out of lungs by birth process.
Adrenaline stress leads to increased surfactant release.
Gas inhaled.
Oxygen vasodilates pulmonary arteries
Pulmonary vascular resistance falls
Right atrial pressure falls, closing foramen ovale.
Umbilical arteries constrict.
Ductus arteriosus constricts.

Question 14

Surfactant

Answer 14

Produced by Type 2 Pneumocytes from 34 weeks gestation.
Dramatic increase in 2 weeks prior to birth.
Type of phospholipid.
Virtual abolition of surface tension.
Allows homogeneous aeration.
Allows maintenance of functional residual capacity.
Increased with steroids and adrenaline.

Question 15

Pulmonary Interstitial Emphysema

Answer 15

Lung cysts - get ruptured - air leaking in alveoli.
Managed - Warmth, Surfactant replacement (if intubated), Oxygen and fluids, Continuous Positive Airway Pressure (maintain lung volumes, reduce work of breathing), Positive pressure ventilation if needed.