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Overview of the Respiratory System

The respiratory system like the cardiovascular system is all about moving stuff around. The cardiovascular system brings blood to every part of the body while the respiratory system focuses on the air you breathe in and out. Before it can find its way into the bloodstream, oxygen has to get into the lungs; plus the carbon dioxide has to find its way out. You accomplish these tasks by breathing air in and out via the respiratory system. This system is divided into two parts: the upper respiratory tract and the lower respiratory tract.

The upper respiratory tract includes the structures that bring air into the body and down to the lower respiratory tract:

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  • Nose: The nose draws in air through the nostrils and into the nasal cavity. The nasal cavity opens into the pharynx (throat) at the nasopharynx.

  • Mouth: The mouth also draws in air, especially during times of physical exertion or when the nose is “stuffy.” The oral cavity opens into the pharynx at the oropharynx.

  • Laryngopharynx: Air passes through the nasopharynx and oropharynx toward the laryngopharynx, which is the opening to the larynx (or voice box).

The lower respiratory tract includes the lungs and the tubes that bring air to them:

  • Trachea: The trachea (or windpipe) continues from the larynx.

  • Bronchi: The trachea splits into two bronchi that each lead to a lung.

  • Lungs: Each lung is divided into lobes. The right lung has three lobes and the left lung has two.

  • Alveoli: The bronchi branch into smaller bronchioles that lead to the alveoli, which are small air sacs surrounded by capillaries. Gas exchange between the air and blood occurs across the alveolar and capillary walls.

As you inhale, the diaphragm lowers, the chest wall expands, and air is drawn into the lungs. As you exhale, the diaphragm moves upward and the chest wall contracts, forcing air out of the lungs, through the trachea, and out the nose or mouth.

Pulmonary disorders refer to diseases involving the lungs. The airways (bronchi, bronchioles, and alveoli) can be affected, the lung tissues can become inflamed, and circulatory diseases can affect the blood vessels. Common pulmonary disorders include asthma, bronchitis, emphysema, and lung cancer.

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