Embryology

Question 1

5 stages of lung development

Answer 1

Embryologic period 
Pseudo glandular period  
Canalicular period
Saccular period
Alveolar period

Question 2

Paracrine factors for budding and branching of the trachea

Answer 2

Shh
Wnt
BMP4

Question 3

Growth factor stimulated by the paracrine factors to induce lung bud formation

Answer 3

FGF10

Question 4

Weeks to the embryological period

Answer 4

4 - 7 weeks

Question 5

Stages within the embryological period

Answer 5

Primary bronchi formation
Secondary bronchi and lobe formation
Tertiary Bronchi formation and bronchopulmonary segmentation

Question 6

Primary bronchi formation

Answer 6

Bronchial lung buds form from the bifurcation of the diverticulum

Question 7

Secondary bronchi formation and lobe formation

Answer 7

Buds enlarge
Right primary bronchial lung bud split into 3/4 secondary bronchial buds
Left primary bronchial lung bud splits into 3 secondary bronchial buds

Question 8

Tertiary bronchi formation and bronchopulmonary segmentation

Answer 8

Secondary bronchial buds branch
Right lung will develop 10 tertiary bronchi
Left lung will develop 8 tertiary bronchi

Question 9

Weeks of the Pseudo glandular period

Answer 9

Weeks 5 - 16

Question 10

Pseudo glandular phase

Answer 10

First ciliated epithelium appear (in humans) by week 13
Like a tubuloacinar gland (tall columnar epithelium at the proximal end and cuboidal epithelium at the distal end).
Developing bronchopulmonary epithelium begins to develop amniotic fluid (present until birth)
Appearance of type II pneumocytes

Question 11

Weeks of the Canalicular period

Answer 11

16-26 weeks

Question 12

Canalicular period

Answer 12

Pulmonary parenchyma
Invasion of capillaries into the mesenchymal tissue
Acini develop from terminal bronchioles
Capillaries surround the acini forming the foundation for gas exchange
Type I pneumocytes (gas exchange) developed from Type II pneumocytes (surfactant production)

Question 13

Weeks of the Saccular period

Answer 13

26 weeks - near terms

Question 14

Saccular period

Answer 14

Saccules form (peripheral airways) and are coated with type I & II pneumocytes. 
Type II pneumocytes begin to secrete surfactant (increasing with term) 
Gas exchange becomes possible.

Question 15

Weeks of the Alveolar period

Answer 15

near term to childhood

Question 16

Alveolar period

Answer 16

First alveoli form in the last few weeks of pregnancy
Capillaries, lymphatics and innervation is completed to allow functional respiration.
1/10th of the 300 million alveoli present at birth

Question 17

Foetal respiratory movements

Answer 17

Regular muscular contractions during the 3rd trimester in preparation for neonatal function
Lack of contractions can lead to lung hypoplasia

Question 18

Foetal to postnatal respiration

Answer 18

lungs remain entirely fluid filled until birth
upper respiratory tract is expired at birth.
Alveoli absorb fluid

Question 19

Dewatering of the lungs

Answer 19

Alveolar epithelial cells change from chloride and fluid secretion to sodium and fluid absorption

Question 20

Abnormalities in lung development

Answer 20

Respiratory distress syndrome (born before the 32nd week) - increased surface tension/reduced gas exchange
oesophageal atresia/tracheoesophageal fistula