Respiratory Embryology

Question 1

why germ layer forms the respiratory system?

Answer 1

endoderm forms the lining of the trachea and bronchial tree

all other lung tissue (smooth muscle, cartilage…) is formed by the by visceral mesoderm

Question 2

tracheoesophageal fistula

Answer 2

an abnormal connection between the oesophagus and the trachea. It’s a common birth defect

Question 3

stages of lung maturation

Answer 3

embryonic (26 days- 6 weeks)
pseudoglandular (6-16 weeks)
canalicular (16-28 weeks)
saccular (28-36 weeks)
alveolar (36 weeks- early childhood)

Question 4

function of type I pneumocytes

Answer 4

they are flattened, thin, squamous: this gives them a thin distance for gaseous exchange

Question 5

function of type II pneumocytes

Answer 5

these retain their cuboidal shape and produce surfactant, which prevents the lungs from collapsing

Question 6

respiratory distress syndrome

Answer 6

causes about 20% of the deaths of all newborns. Occurs due to lungs collapsing due to premature babies not having enough surfactant

Question 7

oesophageal atresia

Answer 7

birth defect which causes the oesophagus to end in a blind-ended pouch rather than connecting normally to the stomach

Question 8

embryonic stage events?

Answer 8

respiratory diverticulum forms. Initial branching gives lungs, lobes and segments

Question 9

pseudoglandular stage event?

Answer 9

14 more generations of branching. Terminal bronchioles

Question 10

canalicular events?

Answer 10

terminal bronchioles–> respiratory bronchioles–> alveolar ducts

Question 11

saccular events?

Answer 11

terminal sacs form, capillaries establish close contact

Question 12

alveolar events?

Answer 12

alveoli mature