Lungs embryology

Question 1

When do the lungs start to develop?

Answer 1

• 4th week of embryogenesis

Question 2

Where does the development of the lungs start from?

Answer 2

• The primitive gut tube (foregut)
• this arises from the endoderm

Question 3

What does the foregut give rise to?

Answer 3

• The respiratory diverticulum
• emerges from the ventral wall of foregut

Question 4

What other parts of the respiratory system are endodermal in origin?

Answer 4

• larynx
• trachea
• bronchi
• lungs

epithelium lining from endoderm

Question 5

What parts arise from the splanchnic mesoderm?

Answer 5

• cartilage
• muscular + connective tissue

splachnic mesoderm surrounds the foregut

Question 6

Initially the diverticulum is continous with the foregut. How do they become seperated?

Answer 6

• Tracheoesophageal septum
• mesodermal folds + tracheoesophageal folds

trachea + lungs buds are ventral and esophagus is dorsal

Question 7

How does the respiratory primordium maintain its communication with the pharynx?

Answer 7

• through the laryngeal orifice

Question 8

What causes tracheoesophageal fistulas + esophageal atresia

clinical note

Answer 8

• Incomplete formation of the tracheoesophageal septum

Question 9

How are primary bronchi formed?

Answer 9

• the diverticulum bifurcates to form the let and righr primary bronchi

Question 10

How is the bronchial tree developed?

Answer 10

• primary bronchi proliferate to give secondary bronchi
• these divide to form 10 tertiary bronchi: bronchopulmonary segments
• branching is regulated by epithelial-mesenchymal interactions

Question 11

How many lobes do the bronchi have?

Answer 11

Right: upper, middle and lower
Left: upper and lower

Question 12

How are the pleural layers developed?

Answer 12

• Visceral pleura: arises from splachnic mesoderm
• Parietal pleura: arises from somatic mesoderm
• space between is pleural cavity

parietal = outer, visceral = inner

Question 13

What is the pseudoglandular period?

Answer 13

• 5-16 weeks
• branching continues to from terminal bronchioles
• no respiratory bronchioles or alveoli

ductus arteriosus shunts blood from pulmonary artery to aortic arch

Question 14

What is the canalicular period?

Answer 14

• 16-26 weeks
• terminal bronchiole divide into respiratory bronchiole

Question 15

What is the terminal sac period?

Answer 15

• 26 weeks ⇒ birth
• alveoli start to develop

Question 16

What two types of cells are found in the alveoli?

Answer 16

• Type I pneumocytes: squamos epithelial, 90%
• Type II pneumocytes: cuboidal epithelial, produce surfactant

Question 17

What is the alveolar period?

Answer 17

• 8 months ⇒ childhood
• alveoli mature + well developed capillaries

Question 18

What is Respiratory distress syndrome?

clinical note

Answer 18

• type II pneumocytes not produced
• surfactant not produced
• difficulty breathing

Question 19

What type of cells line the epithelium of the respiratory tract?

Answer 19

• Psuedostratified columnar epithelium