Fetal Lung Development Flashcards Preview

Block 2: Cardio, Renal, and Respiratory > Fetal Lung Development > Flashcards

Flashcards in Fetal Lung Development Deck (18)
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5 stages of development

Embryonic (4-6 weeks)

Pseudoglandular (6-16 weeks)

Canalicular (17-28 weeks)

Saccular (24-36 weeks)

Alveolar (32 weeks and beyond)


Embryonic stage of lung development

Development of major airways
 and vessels


Pseudoglandular stage of lung development

Bronchi and terminal bronchioles form

And related large blood vessels

6 - 16 weeks


Canalicular stage of lung development

Respiratory bronchioles and alveolar ducts develop

Lumina of bronchi and terminal bronchioles enlarge

Lung tissue becomes highly vascularized

16 - 26 weeks


Saccular stage of lung development

Alveolar ducts give rise to terminal saccules (primordial alveoli) which are initially lined with cuboidal epithelium that turns into squamous epithelium at about 26 weeks

26 weeks to birth

Baby can survive if born at 26 weeks


Alveolar stage of lung development

Alveolar formation

32 weeks to 8 years old


Embryonic stage of VASCULAR development

Vasculogenesis within immature mesenchyme; pulmonary arteries branch from 6th aortic arches; veins as outgrowths from left atrium

< 6 weeks


Pseudoglandular stage of VASCULAR development

Parallel branching of large pulmonary arteries with central airways; lymphatics appear

< 16 weeks


Canalicular stage of VASCULAR development

Increased vessel proliferation and organization into capillary network around airspaces

< 24 weeks


Saccular stage of VASCULAR development

Marked vascular expansion with thinning and condensation of mesenchyme; thin air-blood barrier; double capillary network in septae

< 36 weeks


Alveolar stage of VASCULAR development

Accelerated vascular growth, fusion of double capillary network with thinning of septae

< 2-3 years


Postnatal stage of VASCULAR development

Marked vessel growth and remodeling, as surface area increases greater than 20 fold



Rudimentary mesenchymal cells of embryo differentiate into angioblasts (endothelial cell precursors) and hemangioblasts (RBC precursors)


What are the prenatal, birth, and postnatal mechanics of the pulmonary transition?

Prenatal: increased fetal glucocorticoids cause alveolar maturation; increased adrenaline and AVP during labor cause lung liquid resorption

Birth: umbilical cord clamping causes ductus venosus and umbilical arteries to contract --> increased SVR; first breath of air replace lung fluid, increases O2 and decreases end expiratory lung vol --> decreased PVR, surfactant release, ductus arteriosus closes, foramen ovale closes

Postnatal: alveolar expansion (10 fold by age 18 months - 2 years)


How many alveoli are you born with and how many do you eventually get?

Born with 10 million alveoli

Eventually get 300 million alveoli


Bronchopulmonary dysplasia

Dilated terminal airways

Alveolar simplification

Infants who have RDS (surfactant deficiency) can develop BPD if they get too much inflammation


Things that can lead to BPD

Prolonged supplemental O2

Prolonged mechanical ventilatioin

Postnatal infection



Tracheoesophageal fistula

Usually associated with esophageal atresia

Esophagus connected around bifurcation of trachea (fistula), or esophagus just dead ends/is cut apart (atresia)

Faulty partitioning of foregut into esophagus and trachea during 4th and 5th week of development