Abstract

Description of tracheobronchial tree of lungs with its actual orientation is relatively. A difficult task for students to understand. This could be made easy, if an actual and durable cast of interior of tracheobronchial tree is made available. In tropical countries, the cadavers are usually embalmed for gross Anatomy teaching. It has been observed that embalming has many fallacies. with regard to the irritant and carcinogenic effects of its preservative fluids and its temporary existence in preservation. In this context, plastination can be a better substitute because the preserved anatomical structure is dry, odourless, easy to handle and almost everlasting and also a helpful tool for teaching students.

This economical method can also be helpful for making cast of other hollow viscera.

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Presenter: Avinash Singh

Resource Faculty: Dr. Sarun Koirala

Histology Of The Tracheobronchial TreeHistology Of The Tracheobronchial Tree

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OBJECTIVE

• Microanatomy of Tracheobronchial tree

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DIVISIONS OF TRACHEOBRONCHIAL TREE

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• Mucosa• Lamina Propria• Sub-Mucosa

(Consisting of numerous Serous and Mucous Glands)

• Cartilage• Perichondrium• Adventitia

UPPER RESPIRATORY TRACT

TRACHEA

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1. Mucosa:

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2. Lamina Propria:

3. Sub-Mucosa:

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4. Fibro-muscular – Cartilaginous layer:9

BRONCHI

1. Mucosa:• Pseudo stratified ciliated• Interspersed goblet cell.• Basal cell.• Intermediate cell.• Neuroendocrine cells.• Goblet cell.

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2. Sub-Mucosa:• Smooth Muscles in extra pulmonary bronchi in posterior part - bridging the end

of cartilage.• Smooth Muscles in Intrapulmonary bronchi sub mucosal - arranged in irregular

spiral pattern.• Contraction of this muscle is responsible for folded appearance of mucosa after

death.• Lymphocytes aggregate and lymphoid nodules (BALT) more prominent in

branching point. Function: Immunity

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3. Cartilaginous layer:• Extra pulmonary bronchi - incomplete cartilaginous ring bridge by

fibrocollagenous ligament and Smooth Muscles• Distally on branching as the size of bronchi decreases, cartilage plates decreases

and confined mainly at bifurcation.

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BRONCHIOLES1. Mucosa:• Pseudo stratified ciliated

columnar in larger bronchus.• Simple columnar epithelium in

terminal bronchiole.• Scattered goblet cell in initial

segment only.• Basal cells.• Intermediate cells.• Clara cells.• Neuroepithelial bodies.

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Clara cells:

• Mainly in terminal bronchioles.• No cilia on apical surface.• Does not produce mucus.

Function: Secrets proteins which protect bronchiolar epithelium against oxidative pollutants and inflammation. 14

Neuroepithelial bodies:

•Made from 80-100 cells.•Cytoplasm have secretary granules and receive cholinergic ending.

Function: Chemoreceptor that react to change in gas composition with in

airways.15

2. Lamina Propria: • Comprises of Smooth Muscles and elastic fibers.• Smooth Muscles under control of vagus nerve and sympathetic NS.• Vagal stimulation: Decrease diameter of bronchioles.• Sympathetic stimulation: Increase diameter of bronchioles.

3. Sub-Mucosa:• No cartilage and no glands. 16

DISTAL RESPIRATORY TRACT

1. Respiratory Bronchioles:A. Mucosa:• Ciliated cubical epithelium but

distally cilia disappears.• At the rim of alveolar opening this

epithelium becomes continuous with simple squamous epithelium of alveoli.

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B. Lamina Propria: • Comprises of Smooth muscles and elastic

cartilage.

2. Alveolar duct:• Simple squamous.• Support is by elastic and reticular fibers. • Alveolar duct opens into atria that

communicates with alveolar sac from which arises alveoli.

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3. Alveoli:• Sac like evagination (200 µm in diameter)• 200-400 millions in each normal healthy lung• Honeycomb appearance. Interalveolar septum formed by:• Two thin squamous epithelium layers.• Interstitium

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Function of elastic fiber: Enable the alveoli to expand with inspiration and to contract passively with expiration.

Function of reticular fibers: Support and prevent over distention and also prevent damage to delicate capillaries.

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Diffusion of oxygen and carbon dioxide across the alveoli and

blood separated by BLOOD AIR BARRIER. It is formed by:

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4. Alveolar lining:

A. Type 1 alveolar cell:

• Extremely thin.

• Organelles accumulate around nucleus reducing thickness of blood air barrier.

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B. Type 2 alveolar cell:•Interspersed among type 1 cell.•Histological, cytoplasm contains lamellar bodies which continuously synthesized and release surfactant at surface.•Surfactant composed of: •40 % Dipalmitoyl phosphatidylcholine•40% Other Phospholipid•5% Surfactant Proteins•Cholesterol

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C. Lung Macrophages (Dust cells):

• Present in Interstitium.• Phagocytosis of dust particles and

foreign bodies.

D. Alveolar Pores (Pores of kohn):

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SUMMARY

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Trachea Bronchus

Tertiary bronchus

Bronchiole

Respiratory bronchiole

Epithelium Pseudostratified

Pseudostratified

Columnar Columnar Cuboidal

Clara cells Absent Absent Absent + +

Goblet cells +++ ++ ++ + Absent

Muscularis mucosa

Absent + ++ +++ +++

Mucous glands

+++ ++ + Absent Absent

Cartilage +++ ++ + Absent Absent

Alveoli Absent Absent Absent Absent + 26

MEDICAL APPLICATION

1. In chronic smoking Proportion of ciliated cell : goblet cell is altered to aid in clearing inhaled particles n gaseous pollutants(co, so2).

•No. of goblet cell increase which provide rapid clearance of pollutants but the reduction in no. of ciliated cell results in decrease movement of mucous layer and which eventually leads to congestion of smaller airways.

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2. Bronchial asthma:•Chronic inflammatory disorder.•Hyperactive airways.

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Theodore "T.R." Roosevelt, Jr. was an American author, naturalist, explorer, historian, and politician who served as the 26th President of the United States.

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3. Immotile Cilia Syndrome:

• Autosomal recessive genetic disorder that causes a defect in the action of the cilia lining the respiratory tract (lower and upper, sinuses, Eustachian tube, middle ear) and fallopian tube, and also of the flagella of sperm in males.

• Due to immobility of cilia and flagellum, in some case due to absence of dynein (Protein with ATPase activity that participate in ciliary movement).

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4. Respiratory Distress Syndrome:

• Also Known as hyaline membrane disease of new born.• Lecithin : Sphingomyelin ratio <2

• Patrick Bouvier Kennedy (August 7, 1963 – August 9, 1963) was the youngest child of 35th President United States President John F. Kennedy and First Lady Jacqueline Bouvier Kennedy.

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5. Emphysema:• Destruction of alveolar septa resulting in enlarged air spaces and

a loss of elastic recoil.• Protease/antiprotease imbalance.

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Article [Histological changes induced in the respiratory system with prolonged automatic artificial respiration. (Anatomoclinical study)].

F Beccia, M T Micchia, M ArianoActa anaesthesiologica 02/1968; 19:Suppl 9:110+. Source: PubMed

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Rutgers State University, New jersey

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REFERENCES

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THANK YOU

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