Thorax 05: Development of Lungs and Diaphragm

Question 1

Pericardio-peritoneal canal

Answer 1

A canal that forms between the pericardian and peritoneal cavities during development from which the lungs arise. They are part of the intraembryonic celom

Question 2

Where do the lung parenchyma originate from?

Answer 2

Gut tube

Question 3

Where do the lung stroma originate from?

Answer 3

Splanchnic mesoderm

Question 4

How does the lung initially form?

Answer 4

Active ingrowth from the esophagus to form the respiratory bud, from which form the primary bronchial buds. This is active ingrowth of the esophagus and no budding

Question 5

How may respiratory generations are there? How are they divided?

Answer 5

23 in total: 16 from the conducting zone and 7 from the respiratory zone

Question 6

Pseudoglandular period

Answer 6

Week 5-17, a developmental period marked by the formation of primary, secondary, and tertiary bronchi. Fetus cannot live outside of mother

Question 7

Canalicular period

Answer 7

Weeks 15-25, respiratory bronchioles and terminal saccules form, and the lungs start to become vascular. Pneumocytes start to differentiate. Infant might be able to survive if outside of mother

Question 8

Saccular period

Answer 8

Weeks 24-birth, Most terminal saccules develop, their epithelium thins out, vasculature well developed

Question 9

Alveolar period

Answer 9

Weeks 29- 8 years. Alveoli form. About 95% of them will form after birth

Question 10

How is the pleural sac developed?

Answer 10

Pleural sacs develop from the periocardioperitoneal canals as lungs grow into them. The pleuropericardial membrane folds laterally and then meets below the lungs

Question 11

How is the diaphragm developed?

Answer 11

Septum transversum is pushed caudally during head folding and is pushed behind the forming pleural cavity

Question 12

What are the different developmental sources of the diaphragm

Answer 12

1) Septum transversum becomes central tendon
2) myoblasts become striated muscle
3) mesentery of esophagus
4) Pleuroperitoneal folds make a small portion of adult diaphragm

Question 13

Congenital hiatal hernia

Answer 13

A condition where the left pleuroperitoneal membrane fails to form, resulting from a hole in the diaphragm causing gut contents to protrude into the thorax

Question 14

Laryngotracheal groove

Answer 14

Median outgrowth from caudal end of ventral wall of primordial pharynx (foregut)

Question 15

TRACHEOESOPHAGEAL FISTULA

Answer 15

A disorder in which the trachea and esophagus do not properly separate during development

Question 16

What are the five stages of lung development?

Answer 16

1) embryonic
2) pseudoglandular
3) canalicular
4) saccular
5) alveolar

Question 17

What marker in the amniotic fluid indicates that the lungs have matured? At what point in gestation would this finding be observed?

Answer 17

A lecithin:sphingomyelin ratio > 2 in the amniotic fluid is a marker of fetal lung maturity. Usually observed around week 35of development