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Development of Respiratory System

lungs buds form as outpocketing of gut tube
- formed first from laryngotracheal groove
- closed from oesophagus by tracheo-oesophageal folds
grow into primitive pleural cavity
endothelium of gut provides epithilum of respiratory tract
connective tissue smooth muscle, cartilage provided by surrounding mesoderm
- oesophageal lumen occluded until later in development
from 36 weeks, terminal sacs of bronchioles mature into alveoli, type I and type II cell differentiate
thinng and proliferation of alveoli occurs up to 8 years of age
surfactant secreted late in pregnancy that enables lungs to open easily
abnormal closure of tracheo-oesophageal folds can lead to fistulae often accompanied by occlusion of oesophagus
premature babies often have little or no surfactant production leading to respiratory distress

8.2.1 Development of Respiratory Tract [Embryol]

Formation of endodermal laryngo-tracheal groove and respiratory diverticulum; interaction with surrounding splanchnic mesoderm, branches of 6th arch arteries.
Elongation to form trachea; separation of trachea from oesophagus.	Mesoderm controls budding of endodermal tube.
Bifurcations to form lung buds; formation of bronchial tree.
Growth of lung buds into pleural cavity; differentiation of alveoli, Type I cells, Type II cells; surfactant.	Named stages of lung formation; epithelial occlusion of larynx and oesophagus.
Tracheo-oesophageal fistulas and atresias; Respiratory distress syndrome in premature infants.

8.2.1.1.1 Changes in the lungs at birth [Embryol; Phys]

Change from secretory to absorptive activity of lungs at birth; the first breath; expansion of the lungs with air.
Continuing post-natal development of alveoli.

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