The respiratory system consists of the lungs and air passages. It is responsible for taking in oxygen, a gas needed by all body cells and removing carbon dioxide, a gas that is a metabolic waste product produced by the cells.

Parts of the Respiratory System The nose Pharynx Larynx Trachea Bronchi Alveoli lungs

The nose: has two openings, called nostrils or nares, through which air enters

The pharynx: or throat, lies directly behind the nasal cavities.

The larynx: or voice box, lies between the pharynx and trachea.

Epiglottis: A special leaflike piece of cartilage that closes the opening in the larynx during swallowing.

The trachea: (windpipe) is a tube extending from the larynx to the center of the chest.

The bronchi: The trachea divides into two bronchi near the center of the chest, a right bronchus and a left bronchus. Each bronchus enters the lung and carries air from the trachea to the lung. In the lungs, the bronchi continue to divide into smaller and smaller bronchi until, finally, they divide into the smallest branches, called bronchioles.

Alveoli: Air sacs at the end of terminal bronchioles that resemble a bunch of grapes. An adult lung contains 500 million alveoli.

The lungs: Cone-shaped organs that are made up of a network of pulmonary arteries, veins, bronchi, alveoli and connective tissue. The right lung has 3 sections or lobes: the superior, the middle, and the inferior. The left lung has only 2 lobes: the superior and the inferior. The left lung is smaller because the heart is located toward the left side of the chest.

Cilia Look like hairs that have a “beating” action. The continual sweeping movement of the cilia keeps the lungs clean and free of debris. The cilia may not do their job well with people who have infections, smoke, or are exposed to toxic gases.

Sinuses: Cavities in the skull that surround the nasal area. Lined with a mucous membrane, which warms and moistens air.

Anatomy and Physiology of The Respiratory System Nose Pharynx Larynx Trachea Bronchi Alveoli Lungs

The Airways The airways must be kept clear of debris and secretions. (They may cause blockages or disruptions of gas flow into and out of the lungs.) The airway lining must function properly, because it is the lungs’ defense mechanism. The lining helps protect the lungs from inhaled particles such as pollen, cigarette smoke, dust, and most bacteria.

The Job of the Respiratory System: To bring oxygen gas into the body. To expel the carbon dioxide gas from the body. Respiration is the gas exchange process that takes place in the lungs. (Gas exchange takes place in the alveoli.) Ventilation is what makes respiration happen. (It moves oxygen into the lungs and moves carbon dioxide gas out of the lungs.)

Ventilation: The process of breathing.

Cilia: Tiny hairlike structures that help move the mucous layer that lines the airways pushing trapped particles toward the esophagus, where they can be swallowed.

Inhalation: The process of breathing in air.

Expiration: When the diaphragm (dome-shaped muscle between the thoracic and abdominal cavities) and the intercostal muscles (between the ribs) relax, the process of expiration occurs.