Updated: 11/3/2018

Lung Development

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Snapshot
  • A newborn begins to produce nonbilious emesis after feeds. This is associated with white frothy nasal and oral secretions which recur after suctioning. Physical examination is significant for abdominal distension with crying. A nasogastric tube is unable to fully pass into the esophagus. A plain chest and abdominal radiograph shows excessive air in the stomach. There is coiling of the nasogastric tube in the blind esophageal pouch. (Esophageal atresia with distal tracheoesophageal fistula)
Introduction
 
Phases of Lung Development
Phases
Events
Comments
Embryonic (26 days - 6 weeks)
  • The lung bud developes from an outgrowth of the ventral foregut wall leading to the development of the
    • trachea
    • bronchial buds
    • mainstem bronchi
    • secondary bronchi
    • tertiary bronchi
  • A tracheoesophageal fistula can arise if this stage is negatively affected
Pseudoglandular (6 - 16 weeks)
  • Terminal brochioles are formed
  • At this stage, respirations are impossible
Canalicular (16 - 28 weeks)
  • Terminal bronchioles divide into respiratory bronchioles
  • There is a close apposition between blood vessels and lung epithelium
  • Lung epithelium differentiates into specialized cells such as
    • precursors to type I and II alveolar cells
    • ciliated secretory cells
    • neuroendocrine cells
  • At 25 weeks gestation the fetus is capable of respirations
Saccular (28 - 36 weeks)
  • Primitive alveoli (terminal sacs) are formed from respiratory bronchioles
  • Pneumocytes develop
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Alveolar (36 weeks - ~10 years of age)
  • Maturation of the alveoli
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Questions (1)

(M1.EB.17.4799) Scientists are studying human lung development by trying to identify which proteins and signaling factors trigger lung bud division and bronchiole branching. Their main focus is particularly around the 20th week of gestation, during which terminal bronchioles branch into respiratory bronchioles and further into alveolar ducts. Which of the following phases of embryonic lung development is the stage in which the scientists are interested in studying?

QID: 109317
1

Embryonic

1%

(1/105)

2

Pseudoglandular

4%

(4/105)

3

Canalicular

40%

(42/105)

4

Saccular

27%

(28/105)

5

Alveolar

26%

(27/105)

M 2 D

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