9.1.3 Epithelium of Respiratory Tract: An Impenetrable Barrier Against Microbial Invasion

The respiratory tract is lined with a specialized epithelium that traps and removes microbes and particulate matter from the inhaled air. The anterior part of nasal cavities contains hairs called vestibule, which filter large dust particles. The inner surface of nasal cavities is lined by ciliated mucous epithelium. The mucus secreted by this epithelium traps fine dust particles and microbes. The cilia of the epithelium sweep the trapped particles and microbes posterior to the pharynx, where they are swallowed and eliminated by the digestive system. The trachea and the air passageways within the lungs are also lined by ciliated mucous epithelium that traps fine dust particles and microbes. The cilia in this region propel mucus and foreign particles towards the larynx, where they enter the pharynx and are swallowed.

Definition

Epithelium of Respiratory Tract: The respiratory tract is lined with a specialized epithelium that traps and removes microbes and particulate matter from the inhaled air.

Main Idea

• The anterior part of nasal cavities that contain hairs is called vestibule.
• These vestibular hairs filter the large dust particles of the inhaled air.
• The inner surface of nasal cavities is also lined by ciliated mucous epithelium.
• The mucus secreted by this epithelium is also involved in trapping of fine dust particles and microbes.
• The cilia of the epithelium sweep the trapped, fine dust particles and microbes posterior to the pharynx, where they are swallowed and are eliminated by the digestive system.
• The trachea and the air passageways within the lungs are also lined by ciliated mucous epithelium that is also involved in trapping of fine dust particles and microbes.
• The cilia in this region propel mucus and foreign particles towards the larynx, where they enter the pharynx and are swallowed.

Core Concept

• Vestibule = anterior part of nasal cavities; contains hairs
• Vestibular hairs = filter large dust particles
• Ciliated mucous epithelium = lines inner surface of nasal cavities
• Mucus = traps fine dust particles and microbes
• Cilia = sweep trapped particles and microbes to pharynx
• Trachea = lined by ciliated mucous epithelium
• Air passageways = lined by ciliated mucous epithelium
• Cilia = propel mucus and foreign particles towards larynx

Detailed Explanation

Epithelium of Respiratory Tract: An Impenetrable Barrier Against Microbial Invasion

• The anterior part of nasal cavities that contain hairs is called vestibule.
• These vestibular hairs filter the large dust particles of the inhaled air.
• The inner surface of nasal cavities is also lined by ciliated mucous epithelium.
• The mucus secreted by this epithelium is also involved in trapping of fine dust particles and microbes.
• The cilia of the epithelium sweep the trapped, fine dust particles and microbes posterior to the pharynx, where they are swallowed and are eliminated by the digestive system.
• The trachea and the air passageways within the lungs are also lined by ciliated mucous epithelium that is also involved in trapping of fine dust particles and microbes.
• The cilia in this region propel mucus and foreign particles towards the larynx, where they enter the pharynx and are swallowed.

Summary Table of Respiratory Tract Defences

Summary of the Process

Intermediate Level

Epithelium of Respiratory Tract

Summary of the Process

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Anterior part of nasal cavities contains hairs called vestibule.
• 2. Vestibular hairs filter large dust particles.
• 3. Inner surface of nasal cavities is lined by ciliated mucous epithelium.
• 4. Mucus traps fine dust particles and microbes.
• 5. Cilia sweep trapped particles and microbes to pharynx.
• 6. Particles and microbes are swallowed.
• 7. Particles and microbes are eliminated by digestive system.
• 8. Trachea is lined by ciliated mucous epithelium.
• 9. Air passageways within lungs are lined by ciliated mucous epithelium.
• 10. Cilia propel mucus and foreign particles towards larynx.
• 11. Particles enter pharynx and are swallowed.
• 12. Respiratory tract is an impenetrable barrier.
• 13. It protects against microbial invasion.
• 14. It is part of the first line of defence.
• 15. Smoking damages cilia.

Remember

• - Vestibule = anterior part of nasal cavities; contains hairs
• - Vestibular hairs = filter large dust particles
• - Ciliated mucous epithelium = lines inner surface of nasal cavities
• - Mucus = traps fine dust particles and microbes
• - Cilia = sweep trapped particles and microbes to pharynx
• - Trachea = lined by ciliated mucous epithelium
• - Air passageways = lined by ciliated mucous epithelium
• - Cilia = propel mucus and foreign particles towards larynx

Common Mistakes

• 1. Forgetting the role of the vestibule — Contains hairs; filters large dust particles.
• 2. Mixing up the role of mucus and cilia — Mucus traps; cilia sweep.
• 3. Forgetting the role of the trachea — Lined by ciliated mucous epithelium.
• 4. Mixing up the direction of cilia movement — Towards the pharynx.
• 5. Believing the respiratory tract is sterile — It has defences against microbes.
• 6. Mixing up the defences — Vestibule hairs, ciliated mucous epithelium, cilia.
• 7. Thinking smoking only affects the lungs — Smoking damages cilia.
• 8. Forgetting the role of the digestive system — Eliminates trapped particles.
• 9. Mixing up the locations — Nasal cavities, trachea, air passageways.
• 10. Thinking the respiratory tract is not important — It is an impenetrable barrier.

Quick Revision

The anterior part of nasal cavities that contain hairs is called vestibule. These vestibular hairs filter the large dust particles of the inhaled air. The inner surface of nasal cavities is also lined by ciliated mucous epithelium. The mucus secreted by this epithelium is also involved in trapping of fine dust particles and microbes. The cilia of the epithelium sweep the trapped, fine dust particles and microbes posterior to the pharynx, where they are swallowed and are eliminated by the digestive system. The trachea and the air passageways within the lungs are also lined by ciliated mucous epithelium that is also involved in trapping of fine dust particles and microbes. The cilia in this region propel mucus and foreign particles towards the larynx, where they enter the pharynx and are swallowed.

60-Second Revision

• Vestibule = anterior part of nasal cavities; contains hairs
• Vestibular hairs = filter large dust particles
• Ciliated mucous epithelium = lines inner surface of nasal cavities
• Mucus = traps fine dust particles and microbes
• Cilia = sweep trapped particles and microbes to pharynx
• Trachea = lined by ciliated mucous epithelium
• Air passageways = lined by ciliated mucous epithelium
• Cilia = propel mucus and foreign particles towards larynx
• Warning: Mucus traps; cilia sweep trapped particles to pharynx

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• 9. Immunity

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• 9.2 SECOND LINE OF DEFENCE - NONSPECIFIC DEFENCE

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