Anatomy of trachea & lungs

Anatomy of trachea & Lungs

1. ANATOMY OF TRACHEA & LUNGS Ms.Anu Sebastian: B.Pharm ; M.Pharm Assistant Professor, Dept. Of Pharmacology Nirmala College Of Pharmacy Muvattupuzha,Ernakulam,Kerala

2. TRACHEA/WIND PIPE It is a tubular passageway for air with 12cm length & 2.5cm diameter. It extends from larynx to the superior border of 5 th thoracic vertebrae. Wall is made up of: Mucosa: Psuedostratified ciliated columnar epithelium + lamina propia . Submucosa : Areolar C.T with seromucous glands. Cartilage: 16-20 incomplete hyaline cartilage rings(C-shape). Adventitia: Areolar C.T The open C-shape of cartilage help to accommodate the esophagus. The open part of cartilage is stabilized by elastic C.T & trachealis muscle.

3. Bronchi At the superior border of 5 th thoracic vertebrae the trachea divides into 2 primary bronchus(Left & Right). The primary bronchus contain incomplete rings of cartilages & they are lined by pseudostratified ciliated columnar epithelium. Carina : A ridge at the point where the trachea divides into right & left primary bronchi. The mucous membrane of carina is the highest sensitive area for cough reflex in both trachea & larynx.

4. Primary bronchi Secondary bronchi Tertiary bronchi Terminal Bronchiole Respiratory bronchiole Alveolar duct Alveolar sac Alveoli This arrangement appears like an inverted tree Bronchial tree

5. Fig: Brochioles & Trachea

6. Structural changes in the Bronchial tree Mucous membrane Pseudostratified ciliated col.epithelium -Primary , secondart & tertiary bronchi Ciliated simple col.epithelium -In larger bronchioles. Ciliated simple cuboidal epithelium-In smaller bronchioles. Non Ciliated simple cuboidal epithelium-In terminal bronchioles. Plates of cartilages are replaced by incomplete rings of cartilages & in distal arterioles ,it is absent. As the amount of cartilage decreases-the amount of smooth muscle increases to replace the cartilage.

7. LUNGS These paired cone shaped organs present in the thoracic cavity. The lungs are separated by organs in mediastinum . The lungs are present in the pleural membrane(serous membrane). The outer layer is parietal pleural (lines thoracic cavity). The inner layer is visceral pleural (covers the lungs). The pleural cavity is present between the parietal & visceral layer. Pleural cavity is filled with pleural fluid that decreases the friction. Location: Anterior & Posterior –Ribs Lateral-Ribs Superior- Clavicle Inferior -Diaphragm

8. Fig: structure of Lungs

9. Fig: Structure of Lungs

10. The base is broad & the apex is tapered /narrow. The anterior & posterior surfaces are known as costal surface as it faces the ribs.The lateral surface is known as mediastinal surface as I faces the mediastinum . The mediastinal surface contains a depression called hilum.The blood vessels,bronchi etc enter the lungs through the hilum . A concavity called cardiac notch is present in the left lung. The right lung is more thicker & broader than left.

11. Lobes ,Fissures & Lobules The left lung is divided into two lobes by oblique fissure. The right lung is divided into three lobes by oblique 7 horizontal fissure. Each lung receives a primary bronchi & each lobe receives secondary bronchi. The right lung is having 3 & left is having 2 secondary bronchi. Each lobe is divided into bronchopulmonary segment & it receives a tertiary bronchi. Each bronchopulmonary segment is divided into lobules. Each lobule contains arteriole,venule,lymphatic vessel, & terminal bronchiole. The terminal bronchiole divides into respiratory bronchiole. The respiratory bronchiole divides into alveolar ducts, then into alveolar sacs & finally alveoli.

12. ALVEOLI It is cupshaped outpouching lined by simple sq. epithelium & covered by thin elastic membrane. Each alveolar sac consist of 2/3 alveoli. The wall of alveoli is composed of : T wo types of epithelial cells: a)Type 1 alveolar cells-simple sq.epithelium b) Type II alveolar cells- in between type 1.It is simple cuboidal epithelium .The surface contains microvilli , secretes alveolar fluid. Alveolar macrophages-it removes the dudt & debis . Fibroblast- It produce reticular & elastic fibres .

13. Respiratory Membrane It is the wall through gaseous exchange takes place. The membrane consist of 4 layers A layer of Type I & Type II alveolar cells + macrophages. An epithelial basement membrane underlying the alveolar wall. A capillary basement membrane Capillary endothelium. The thickness is 0.5 µm. Each lung has 300 million alveoli(70 m ² area )

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