Part 3: Airways and Anatomy — The Lungs and Their Protective Layer

In Part 2, we traced the journey of air through the upper and lower airways. In this section, we focus on the lungs themselves — their structure, protective mechanisms, and how they support efficient breathing while guarding against injury and infection.

1. The Lungs: Structure and Position

The lungs are two spongy, elastic organs located on either side of the chest cavity.

• The right lung has three lobes

• The left lung has two lobes, allowing space for the heart

Their flexible structure allows them to expand and contract with each breath, adapting to the body’s oxygen demands.

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2. Pleura: The Lungs’ Protective Covering

Each lung is surrounded by a double-layered membrane called the pleura.

• The visceral pleura covers the lung surface

• The parietal pleura lines the chest wall

A thin layer of pleural fluid between these layers reduces friction, allowing smooth lung movement during breathing.

Disruption of this system — such as in pleural effusion or pneumothorax — restricts lung expansion and causes breathing difficulty.

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3. Bronchial Walls and Airway Defense

The inner lining of the bronchi and bronchioles is equipped with:

• Cilia, tiny hair-like structures that move mucus upward

• Mucus, which traps dust, pathogens, and pollutants

This self-cleaning mechanism, known as the mucociliary escalator, is a primary defense against respiratory infections.

Smoking and air pollution damage cilia, allowing harmful particles to settle deep within the lungs.

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Key Takeaway

The lungs are more than air-filled sacs — they are highly protected, flexible organs designed for efficient oxygen delivery and continuous self-defense. Damage to their structure or protective layers directly affects breathing efficiency and respiratory health.

In Part 4, we’ll examine how breathing is mechanically controlled — focusing on the diaphragm, chest wall, and muscle coordination that power every breath.