The document summarizes the key components and functions of the respiratory system. It describes how air enters the body through the mouth or nose and passes through the pharynx, larynx, trachea, bronchi and into the lungs. The lungs contain alveoli where the exchange of oxygen and carbon dioxide occurs. Contraction of the diaphragm causes inhalation by expanding the chest cavity, while relaxation causes exhalation by contracting the chest cavity.

1. Mouth,
larynx, From the pharynx, air enters into the larynx, commonly called the voice box. The
larynx is part of the upper respiratory tract that has two main functions: a passageway for air
to enter into the lungs, and a source of vocalization. The larynx is made up of the hyoid bone
and cartilage, which helps regulate the flow of air. The epiglottis is a flap-like cartilage
structure contained in the larynx that protects the trachea against food aspiration.
pharynx, Besides the nose, air can enter into the lungs through the mouth. The pharynx is a
tubular structure, positioned behind the oral and nasal cavities, that allows air to pass from
the mouth to the lungs. The pharynx contains three parts: The nasopharynx, which connects
the upper part of the throat with the nasal cavity; the oropharynx, positioned between the top
of the epiglottis and the soft palate; and the laryngopharynx, located below the epiglottis.
trachea,
bronchi, The bronchi allow the passage of air to the lungs. The trachea is made of c-shaped
ringed cartilage that divides into the right and left bronchus. The right main bronchus is
shorter and wider than the left main bronchus. The right bronchus is subdivided into three
lobar bronchi, while the left one is divided into two lobar bronchi.
lungs The lungs are spongy, air-filled organs located on both sides of the chest cavity. The left lung is
divided into a superior and inferior lobe, and the right lung is subdivided into a superior, middle, and
inferior lobe. Pleura, a thin layer of tissue, line the lungs to allow the lungs to expand and contract with
ease.
Respiration is the primary function of the lungs, which includes the transfer of oxygen found in the
atmosphere into the blood stream and the release of carbon dioxide into the air.
, alveoli, The average adult has about 600 million alveoli, which are tiny grape-like sacs at the
end of the respiratory tree. The exchange of oxygen and carbon dioxide gases occurs at the
alveolar level. Although effort is required to inflate the alveoli (similar to blowing up a balloon),
minimal effort is needed to deflate the alveoli (similar to the deflating of a balloon).
capillaries,
diaphragm The diaphragm is a muscular structure located between the thoracic and
abdominal cavity. Contraction of the diaphragm causes the chest or thorax cavity to expand,

2. which occurs during inhalation. During exhalation, the release of the diaphragm causes the
chest or thorax cavity to contract.
reference
http://www.md-health.com/Function-Of-Organs-In-Respiratory-System.html