-
Pregnancy Term Begins
-
Period: to
Pregnancy Term
-
Week 4: Embryonic Stage Begins
Endoderm, Mesoderm, and Intraembryonic Coelom take place
Lung buds sprout as a growth from the ventral wall of the foregut, also where lobar division takes place -
Week 5: Embryonic Stage Ends, Pseudoglandular Stage Begins
Tubular branching continues, all segmental bronchi become present, stage is critical for formation of conducting airways
epithelial tubes surrounded by mesenchyme are formed -
Week 16: Canalicular Stage Begins
bronchioles produced, capillaries in contact with cuboidal epithelium increase, alveolar epithelium begins to develop, future gas exchange regions can be identified -
Week 17: Pseudoglandular Stage Ends
-
Week 24: Saccular Stage Begins
air sacs and alveolar ducts become developed, vascular tree grows, gas exchange region expands, fibroblastic cells produce extracellular matrix, collagen and elastin, saccules form -
Week 25: Canalicular Stage Ends
-
Week 35: Alveolar Stage Begins
number and size of capillaries and alveoli increase, amniotic fluid and respiratory motions aid in lung maturation, microvascular maturation occurs -
Week 40: Saccular Stage Ends
-
8 years Later: Alveolar Stage Ends
Lung and Respiratory System fully developed
