1. Paranasal Air Sinuses Diverticula grow from nasal cavity walls into surrounding bones Openings of outgrowths persist as orifices of adult sinuses At Birth- no frontal or sphenoidal sinuses Maxillary-3-4 mm Ant & post Ethmoidal- Few cells

2. Paranasal Air Sinuses Ethmoidal- small uptil 2 yrs grows rapidly 6-8 yrs Maxillary- grows slowly till puberty, fully developed in adulthood Frontal grows from ant ethmoidal-2yrs rapid dev. 7yrs Sphenidal-grows from post. Eth. 2 yrs

3. Pharyngeal arches & primordial Pharynx

4. Laryngotracheal groove

5. Trachea & Oesophagus

6. Larynx 4 wks5 wks 6wks 10 wks

7. Bronchi 4 th wk-lung bud 5 th wk-bronchial buds 6 th wk-angiogenetic mesenchyme around prim. Br. 7 th wk- tertiary br., bronchopul. Seg. Formed 24 wks-17 orders of bronchi formed After birth- 7 orders

8. Stages of Lung Development

9. Histogenesis Splanchnic Mesoderm Connective tissue Cartilage Muscle Capillaries Visceral pleura Somatic Mesoderm Parietal pleura Endoderm epithelium

10. Histogenesis

11. Stages of Lung Development Pseudoglandular phase 7-17 wks Development of lower conducting airway & acini Lung resembles exocrine gland Epithelium-mesenchyme interactions Airway epithelium differentiates Mucous glands-12wks enlarge, 14 wks-secretion Sm. M & CT differentiate No gaseous exchange

12. Stages of Lung Development Canalicular phase 17-26 wks Overlaps with pseudoglandular phase Lumina of bronchi enlarge 3 generations of branching Resp. br. & alveolar ducts formed Saw–toothed margins of distal regions –acini Type I & II pneumocytes Surfactant - 6 months Gaseous exchange possible

13. Stages of Lung Development

14. Stages of Lung Development Sacular / terminal sac phase 24 wks – birth More terminal sacs with thin epithelium Type I & II alveolar cells – surfactant increases Interstitial tissue decreases Cap.plexus–double cap. layer between alveoli Elastin deposited beneath ep. Lymphatics develop Fetus can survive if born

15. Stages of Lung Development Alveolar phase Late fetal period – childhood Thinning of alveolar lining cells, thin alveolocapillary membrane- gaseous exchange is easy Increase in no. of alveoli 50 million at full term(1/6 adult no.) Fusion of cap. nets of adjacent alveoli

16. Stages of Lung Development

17. Tracheo-Oesophageal Fistula

18. Congenital anomalies of lungs Lobe of Azygous V Congenital Pul. Cysts Lung Agenesis Lung Hypoplasia Accessory Lung Abnormal fissures Abnormal lobes