The document summarizes the anatomy and structure of the trachea, bronchi, lungs, and alveoli. It notes that the trachea is a tubular passageway that extends from the larynx to the superior border of the 5th thoracic vertebrae. The trachea divides into two primary bronchi at this point. The primary bronchi then branch further into secondary and tertiary bronchi, bronchioles, and terminal bronchioles in an inverted tree-like structure called the bronchial tree. The lungs are located in the thoracic cavity and are made up of lobes separated by fissures. Each lobe contains bronchopulmonary segments that divide further into lobules containing alveoli, which

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 )

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