Respiratory System Anatomy: A Complete Guide to Organs and Structures

Upper Airway

The upper airway serves as the entry point for air, conditioning it before it reaches the lungs. It includes the nose, pharynx, and larynx.

Nose

The nose comprises the nostrils, nasal septum, turbinates (which warm and humidify air), paranasal sinuses, and the adenoids (lymphoid tissue that helps trap pathogens).

Pharynx

The pharynx is a muscular tube divided into three regions: the nasopharynx (behind the nose), oropharynx (behind the mouth), and laryngopharynx (above the larynx). It serves both respiratory and digestive functions.

Larynx

Often called the voice box, the larynx houses the epiglottis (which prevents food from entering the airway), the vocal cords (for sound production), and the arytenoid and cricoid cartilages that provide structural support.

Lower Airway

The lower airway conducts air into the lungs and begins at the trachea.

Trachea

The trachea, or windpipe, is reinforced with C-shaped cartilaginous rings that keep it open. Its inner lining (mucosa) traps particles and moves them upward via cilia.

Bronchi

The trachea bifurcates into the primary bronchi, which further divide into secondary and tertiary bronchi, distributing air to each lung lobe.

Bronchioles

These smaller airways lack cartilage and end in terminal bronchioles, which lead to respiratory bronchioles where gas exchange begins.

Lungs and Gas Exchange

The lungs are the primary organs of respiration, housed within the pleural cavities.

Pleura

The visceral pleura covers the lungs, while the parietal pleura lines the thoracic cavity. The pleural space between them contains lubricating fluid for smooth movement.

Lobes

The right lung has three lobes (upper, middle, lower) and the left lung has two (upper, lower) to accommodate the heart.

Alveoli and Pulmonary Capillaries

Alveoli are tiny air sacs where oxygen and carbon dioxide are exchanged with the blood in the surrounding pulmonary capillaries.

Respiratory Muscles

Breathing is driven by muscular effort.

Diaphragm

The dome-shaped diaphragm is the primary inspiratory muscle; its contraction increases thoracic volume, drawing air in.

Intercostal Muscles

The external intercostals assist inspiration by lifting the ribs, while the internal intercostals aid forced expiration.