Breathing is automatic process that people rarely think about.  Oxygen enters our lungs with the air that we breathe through the nose or mouth and then passes through the pharynx, larynx, trachea, to the right and left bronchi, and continues through the bronchial tubes to the alveoli.  The bronchial tubes branch off as many as 25 times before reaching the alveoli. There are about 300 million alveoli. Oxygen is absorbed into the blood vessels within the alveoli.  The blood then carries oxygen to the body.  As oxygen is entering the blood vessels, carbon dioxide leaves the blood vessels and enters the alveoli and is eliminated when the person breathes out.

Nose

•  Acts as a filter, hairs (cilia) and mucus inside the nostril trap large and fine particles and move mucus out of the nose.

•  The cleansing process is aided by sniffing, sneezing and nose blowing.

•  Air is warmed to about 95 degrees F.

•  Air is humidified as it passes the nasal turbinates to about 97%.

Pharynx

•  Location of eustachian tube opening.

•  Epiglottis closes over trachea during swallowing in the pharynx, preventing food from going into the airways.

 Larynx

•  Vocal cords are essential for speech.

 Trachea

•  The windpipe that brings air into the lungs.

 Bronchi

•  Right and left mainstem bronchi branch off the trachea and deliver air to the right and left lung.

 Bronchial Tubes and Bronchioles

•  The bronchial tubes continue to divide into smaller and smaller bronchioles.

•  The bronchioles are wrapped with smooth muscle.

•  The lining membranes of the airways contain cilia which facilitates movement of mucus out of the airways. They also contain goblet cells which produce mucus.

 Alveoli

• A very tiny air sac at the end of the bronchioles.

• The alveoli are wrapped with blood vessels that exchange oxygen for carbon dioxide and this is the main function of the lungs.

• If the alveoli are damaged by substances, i.e. cigarette smoke, they cannot be repaired.

 Pulmonary Muscles

•  The diaphragm is largest muscle in the pulmonary system.  It separates the chest cavity from the abdominal cavity.  When the diaphragm moves down or contracts, the lungs expand allowing more space for air.  When the diaphragm moves up or relaxes, it forces air out of the lungs.

•  There are other muscles located in the chest wall that assist in breathing.  During an asthma attack the muscles must work harder to move air in and out of the lungs.

•  The trachea and the bronchial tubes are wrapped with smooth muscles.  These muscles are involuntary.