The Respiratory System

Anatomy of the Respiratory System

This lesson introduces the anatomy of the respiratory system and how each organ within this system functions. It also discusses the mechanics of breathing and respiration.

Every living thing requires oxygen for survival. Humans can live for days without water and for weeks without food. But they can only survive a few minutes without air. The respiratory system’s primary function is to bring oxygen into the body, in exchange for carbon dioxide. As shown in the following image, organs of the respiratory system include the nose, nasal cavity, mouth, larynx, pharynx, lungs, and diaphragm.

The respiratory organs can be divided into the upper and lower respiratory tract. The upper respiratory tract includes the nasal cavity, pharynx, and larynx. The trachea, bronchus, and lungs belong to the lower respiratory tract. The nasal cavity opens to the nose. The nose and nasal cavity warm and moisten air as a person breathes. As a defensive mechanism, tiny nose hairs and mucus produced by the epithelial mucosa cells in the nose help prevent particles in the air from entering the lungs.

Behind the nasal cavity is the pharynx. Both food and air pass through this long tube. Just below the pharynx is the larynx, or voice box. It channels air to the trachea and pushes food past the epiglottis, which covers the trachea during swallowing to prevent food from entering the lungs. Once food passes the epiglottis, it moves toward the esophagus. When air reaches the trachea, or windpipe, it travels down a long tube that branches into bronchi. The bronchi enter the lungs. As shown in the image, the bronchi branch into bronchioles before reaching tiny air sacs in the lung called alveoli. Gas exchange occurs in the alveolar region.

The diaphragm is a muscle that plays a large role in breathing. It is found at the base of the lungs and spreads across the bottom of the rib cage, forming the chest cavity. The human body has two lungs that vary in size and weight. The right lung, which is larger and heavier, has three lobes. The left lung has two lobes.

Pulmonary surfactant consists of chemical compounds that lines the alveolar surfaces of the lungs. They are lipopolysaccharides which have both a hydrophobic and hydrophilic layer to help keep the lungs inflated or prevent them from collapsing. On the outside of the lungs are serous membranes that cover each lung, called pleura. They form a two-layered membrane that cushions the lungs while reducing friction between the lungs and chest cavity or rib cage.

Did You Know?

The total surface area of the alveoli in the lungs is roughly the size of a tennis court. Such a large surface area is needed to facilitate gas exchange and ensure the body is oxygenated at all times.

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