Embryology of Respiratory System

Question 1

During what week of pregnancy does the trachea and lung buds begin to develop

Answer 1

week 4

Question 2

Where and from what structure does the trachea emerge

Answer 2

the ventral wall of the foregut from the laryngotracheal groove

Question 3

What structure develops to separate the trachea and oesophagus

Answer 3

the oesophagotracheal septum

Question 4

What is a fistula

Answer 4

a passage that forms between two tubular organs e.g. trachea and oesophagus during deveopment

Question 5

What is an atresia

Answer 5

where a passage in the body is closed or absent (can occur in the primitive oesophagus if a fistula is present

Question 6

How does the pleural cavity and pleura develop

Answer 6

• visceral pleura from splanchnic mesoderm
• parietal pleura from somatic mesoderm
• pleural cavity from intra-embryonic coelom

Question 7

How do the lung buds develop

Answer 7

• they invaginate into the visceral pleura/splanchnic mesoderm and continue to develop

Question 8

Name the three periods of lung bud differentiation

Answer 8

• embryonic
• foetal
• postnatal/alveolar

Question 9

What happens during the embryonic stage

Answer 9

• the trachea emerges from the laryngotracheal groove and forms two lateral pockets
• vascular connections develop

Question 10

What three stages can the foetal period be divided into

Answer 10

• pseudoglandular
• canalicular
• saccular

Question 11

What happens during the pseudoglandular stage

Answer 11

setup of all pulmonary structures except elements needed for gas exchange

Question 12

What happens during the canalicular stage

Answer 12

• terminal bronchioles develop tubes of the respiratory part if the lung
• epithelium develops into cuboidal secretory (type 2) and flat (type 1) cells

Question 13

What happens during the saccular stage

Answer 13

• formation of alveolar sacs

- initially divided by primary septa, will be divided further by secondary septa to give rise to alveoli

Question 14

What happens during the alveolar stage

Answer 14

• formation of alveoli
• alveolar enlargement
• respiratory bronchioles increase in number

Question 15

Give some examples of congenital conditions that can develop during development

Answer 15

• IRDS/hyaline membrane disease
• accessory lobe formation
• azygos lobe formation (lung growth around azygos vein)
• lung agenesis (non-development of lung buds)

Question 16

What four embryonic components make up the diaphragm

Answer 16

• septum transversum
• two pleuroperitoneal membranes
• oesophageal dorsal mesentery
• muscular ingrowth from lateral body walls

Question 17

What does the septum transversum develop into

Answer 17

central tendon

Question 18

What do the pleuroperitoneal membranes and peripheral body wall muscle develop into

Answer 18

peripheral, muscular part

Question 19

What does the oesophageal mesentery develop into

Answer 19

diaphragmatic crura

Question 20

Where is the septum transversum located in the developing embryo initially

Answer 20

• opposite the somites at C3-C5

- migrates caudally during diaphragm development and brings its innervation with it

Question 21

What are three main defects that can occur relating to the diaphragm

Answer 21

• failure to completely close
• herniation (diaphragmatic/hiatal)
• pulmonary hypoplasia (incomplete lung development)_