1. 5/4/2015 1 DEVELOPMENT OF TRACHEA, LUNGS & DIAPHRAGM LECTURE BY PROF. DR.ANSARI (for MBBS students only) Monday, May 04, 2015 Monday, May 04, 2015

2. 5/4/20152 Objectives Development of trachea, Lungs Diaphragm Anomalies

3. 5/4/20153 Laryngotracheal diverticulum The respiratory system develops in about the fourth week. The laryngotracheal diverticulum arises from endoderm on the ventral wall of the foregut. The caudal end of the laryngotracheal diverticulum enlarges to form the lung bud, which is surrounded by splanchnic mesenchyme.

4. 5/4/20154 Larynx The opening of the laryngotracheal tube becomes the inlet of the larynx. The laryngeal cartilages are derived from the fourth and sixth pharyngeal arches.

5. 5/4/20155 Trachea The epithelium and glands of the trachea develop from the endoderm of the laryngotracheal tube. The cartilage, connective tissue, and smooth muscle are derived from the surrounding splanchnic mesenchyme.

6. 5/4/20156 Development of lungs

7. 5/4/20157 The lung buds Are endodermal in origin. On the right side the lung bud further divides in to 3 lobes. On the left side the lung bud divides into 2 lobes. The pneumocytes type I and II are endodermal in origin. The blood capillaries arise from the surrounding splanchnopleuric mesoderm.

8. 5/4/20158 The fetal lungs Are nonfunctional before birth, they are solid glandular structures. After birth the first cry of life, opens up the lung alveoli and pulmonary circulation established. The pulmonary arteries bring deoxygenated blood from the right ventricle. The oxygenated blood leaves by the pulmonary veins into left atrium.

9. 5/4/20159 Clinical correlations Tracheoesophageal Fistula An abnormal communication between the trachea and esophagus due to incomplete separation of the trachea and esophagus during the fourth week of development.

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12. 5/4/201512 Respiratory Distress Syndrome Respiratory Distress Syndrome is common in premature infants and is due to a deficiency of surfactant

13. 5/4/201513 Pulmonary Hypoplasia Pulmonary hypoplasia results when lungs are compressed by congenital posterolateral diaphragmatic hernia.

14. 5/4/201514 Diaphragm development

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16. 5/4/201516 Innervations of diaphragm The muscle of the diaphragm is derived from the 3,4, & 5th cervical somites Motor innervations is therefore from C3,4,5 via the phrenic nerve. Sensory innervation is also from the phrenic, a thin rim around the costal margin being innervated by the lower six intercostal nerves.

17. 5/4/201517 Congenital diaphragmatic hernia The most common congenital defect of the diaphragm is congenital diaphragmatic hernia. This results from defective formation and fusion of the pleuroperitoneal membranes with the other three parts of the diaphragm.