Respiratory tract

The respiratory tract is the subdivision of the <a href="/facts/Respiratory_system/IG8v5JEr">respiratory system</a> involved with the process of conducting air to the <a href="/facts/Pulmonary_alveolus/aEHP1ATT">alveoli</a> for the purposes of <a href="/facts/Gas_exchange/3vUewPNH">gas exchange</a> in <a href="/facts/Mammal/phSwTzBo">mammals</a>. The respiratory tract is lined with <a href="/facts/Respiratory_epithelium/gsvl9IJL">respiratory epithelium</a> as respiratory mucosa.
Air is breathed in through the <a href="/facts/Nose/Kv0lv34S">nose</a> to the <a href="/facts/Nasal_cavity/N82Yw4LR">nasal cavity</a>, where a layer of <a href="/facts/Nasal_mucosa/ndEF4os6">nasal mucosa</a> acts as a filter and traps pollutants and other harmful substances found in the air. Next, air moves into the <a href="/facts/Pharynx/51F3eVms">pharynx</a>, a passage that contains the intersection between the <a href="/facts/Esophagus/XWa7WoWn">oesophagus</a> and the <a href="/facts/Larynx/0bhtXI3Q">larynx</a>. The opening of the larynx has a special flap of cartilage, the <a href="/facts/Epiglottis/QEgccjVK">epiglottis</a>, that opens to allow air to pass through but closes to prevent food from moving into the airway.
From the <a href="/facts/Larynx/0bhtXI3Q">larynx</a>, air moves into the <a href="/facts/Trachea/zMSEwjAy">trachea</a> and down to the intersection known as the <a href="/facts/Carina_of_trachea/z5gKXHrM">carina</a> that branches to form the right and left primary (main) <a href="/facts/Bronchus/t83cUXou">bronchi</a>. Each of these bronchi branches into a <a href="/facts/Bronchus/t83cUXou">secondary (lobar) bronchus</a> that branches into <a href="/facts/Bronchus/t83cUXou">tertiary (segmental) bronchi</a>, that branch into smaller airways called <a href="/facts/Bronchiole/2mPRrpQs">bronchioles</a> that eventually connect with tiny specialized structures called <a href="/facts/Pulmonary_alveolus/aEHP1ATT">alveoli</a> that function in <a href="/facts/Gas_exchange/3vUewPNH">gas exchange</a>.
The <a href="/facts/Lung/gTWXI6Fj">lungs</a> which are located in the <a href="/facts/Thoracic_cavity/4N5W74rF">thoracic cavity</a>, are protected from physical damage by the <a href="/facts/Rib_cage/KzXLlujq">rib cage</a>. At the base of the lungs is a sheet of skeletal muscle called the <a href="/facts/Thoracic_diaphragm/aw7KcUou">diaphragm</a>. The diaphragm separates the lungs from the <a href="/facts/Stomach/Q4PPDGT6">stomach</a> and <a href="/facts/Gastrointestinal_tract/nK2zwqBS">intestines</a>. The diaphragm is also the main <a href="/facts/Muscles_of_respiration/SQ5fy9hy">muscle of respiration</a> involved in <a href="/facts/Breathing/92Wov2gk">breathing</a>, and is controlled by the <a href="/facts/Sympathetic_nervous_system/hs8psNRd">sympathetic nervous system</a>.
The lungs are encased in a <a href="/facts/Serous_membrane/vj8eDs43">serous membrane</a> that folds in on itself to form the <a href="/facts/Pulmonary_pleurae/A5E7jwNe">pleurae</a> – a two-layered protective barrier. The inner <a href="/facts/Pulmonary_pleurae/A5E7jwNe">visceral pleura</a> covers the surface of the lungs, and the outer <a href="/facts/Pulmonary_pleurae/A5E7jwNe">parietal pleura</a> is attached to the inner surface of the thoracic cavity. The pleurae enclose a cavity called the <a href="/facts/Pleural_cavity/Wel4Tz7p">pleural cavity</a> that contains <a href="/facts/Pleural_cavity/Wel4Tz7p">pleural fluid</a>. This fluid is used to decrease the amount of friction that lungs experience during breathing.

Respiratory tract open-in-new

Respiratory tract