Respiratory Development

Question 1

What event/structure formations marks the beginning of respiratory development?

Answer 1

a laryngotracheal groove appears in the ventral side of the caudal primordial pharynx

the trachiobronchal tree begins to develop caudal to the fourth pair of pharyngeal pouches

Question 2

What happens to the laryngotracheal groove next?

Via what signals?

What does this form?

Answer 2

• evagination of the laryngotracheal groove via transcription factor TBX4 forms the pouch-like lung bud

(or laryngotracheal diverticulum… or respiratory diverticulum)

Question 3

What happens to the lung bud as respiratory development continues?

Answer 3

• lung bud elongates
• splanchnic mesenchyme fills in the elongated bud
• the respiratory bud

Question 4

What separates the trachea and esophagus after the respiratory diverticulum buds off of the foregut?

Answer 4

the esophagotracheal ridge

Question 5

How is the branching of the respiratory tree initiated?

What is the name for this kind of branching and why?

Answer 5

Mesenchymal signals initiate the division

dichotomic divison because each branch gives 2 new branches

Question 6

What gives the epithelium?

What gives the other parts of the respiratory system structure and what are they?

Answer 6

endoderm gives epithelium

splanchnic mesoderm gives the cartilage, muscle, CT

Question 7

What are the 4 stages of lung development?

Answer 7

1. pseudoglandular
2. canalicular
3. saccular
4. alveolar

Question 8

What is the 1st of the 4 stages of lung development and what takes place during it?

Answer 8

pseudoglandular

• growth and branching occurs
• all pulmonary structures are set up except gas exchange elements

Question 9

What is the 2nd of 4 stages of lung development?

What happens in this stage?

(3 main processes)

Answer 9

Canalicular

• Septation - airspaces multiply via partitioning (terminal bronchioles > canaliculi > alveolar ducts)
• Differentiation - into flat and secretory cells (type I and II)
• Vascularization - develops in lungs

Question 10

What is the 3rd of the 4 stages of lung development?

What happens?

Answer 10

Saccular

• primary septa form alveolar sacs
• capillaries contact alveolar sacs

Question 11

What is the 4th and final stage of lung development?

What happens during it?

What is special about this stage?

Answer 11

Alveolar Stage

• alveolarization - alveolar sacs divide into alveoli
• this stage occurs mostly postnatally, beginning at week 41 and lasting until 2 years after birth