Anatomy of trachea & Lungs

1. 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 5th 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 5th 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 :
 Two 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
1. A layer of Type I & Type II alveolar cells + macrophages.
2. An epithelial basement membrane underlying the alveolar
wall.
3. A capillary basement membrane
4. Capillary endothelium.
 The thickness is 0.5 µm.
 Each lung has 300 million alveoli(70 m² area )

14. THANK YOU