Development Of The Lungs

1. Development

-laryngotracheal diverticulum forms in ventral wall of foregut

-tracheoesophageal septum divides foregut into esophagus and trachea

-distal end of LTD enlarges to form lung bud

-lung bud > 2 bronchial buds > primary, secondary, tertiary bronchi = bronchopulmonary segments

-4 stages

1. Glandular (Weeks 5-17)

-respiration not possible, premature fetuses cannot survive

2. Canalicular (Weeks 13-25)

-respiratory bronchioels and terminal sacs; vascularization increases

3. Terminal Sac (Weeks 24-birth)

-Type I and II pneumocytes, respiration possible

-Premature fetuses weeks 25-28 can survive

4. Alveolar (Birth-year 8)

-resp. bronchioles, terminal sacs, alveolar ducts and alveoli increase in number

2. Congenital anomalies

1. Tracheosophageal fistula

-abnormal communication b/t trachea and esophagus; malformation of septum

-sx: gagging and cyanosis after feeding, abd. distention after crying, reflux of gastric contents into lungs

2. Respiratory distress syndrome

-deficiency of surfactant

-common in premature infants, infants with diabetic mothers, fetuses with prolonged IU asphyxia

-tx: thyroxine and cortisol to mother

3. Pulmonary hypoplasia

-secondary to congenital diaphragmatic hernia (into pleural cavity) and bilateral renal agenesis

Category: Anatomy Notes