Anatomy of the Respiratory System

The Structures That Help You Breathe

The respiratory system is a complex network of organs and tissues that work together to bring oxygen into your body and remove carbon dioxide. Understanding these structures is the first step toward better respiratory health.

The Upper Respiratory Tract

Breathing begins at the nose and mouth. The nasal cavity warms, humidifies, and filters incoming air. Tiny hairs called cilia and a layer of mucus trap dust, allergens, and pathogens before they reach the lungs. The air then passes through the pharynx (throat) and larynx (voice box) before entering the trachea.

The Lower Respiratory Tract

The trachea (windpipe) divides into two main bronchi, one leading to each lung. These bronchi branch into smaller and smaller tubes called bronchioles, which end in tiny air sacs known as alveoli. An adult lung contains approximately 300 million alveoli, providing an enormous surface area — roughly the size of a tennis court — for gas exchange.

The Lungs and Pleura

The lungs sit within the thoracic cavity, protected by the ribcage. Each lung is surrounded by a double-layered membrane called the pleura. A thin film of fluid between these layers reduces friction during breathing. The right lung has three lobes, while the left lung has two lobes to accommodate the heart.