Which of the following is not part of the upper respiratory tract?
Breathing occurs through the respiratory system and represented by the respiratory channel, lungs, respiratory muscles, nerve structures controlling functions. Same as the blood and cardiovascular system transporting carbon dioxide and breathing oxygen.
The breathing system consists of the upper (nasal cavities, nasopharynx, stomatopharynx) and lower (gorge, air-vessel, extra and intrapulmonary air tubes) part.
Oxygen and breathing system
For a normal functioning, the breathing system should deliver about 250-280 ml of oxygen per minute under relative rest conditions and reject approximately the same amount of carbon dioxide gas
Through this system, the human body is constantly in contact with atmospheric air – the external environment, which may contain microorganisms, viruses, harmful substances of a chemical nature.
They all are capable to penetrate into the human organism and cause the development of many diseases. Some of them are rapidly spreading or epidemic (influenza, acute respiratory viral infections, tuberculosis, etc.).
Important: A big threat to human health happens because of air pollution with chemicals of technogenic origin (hazardous industries, motor vehicles).
One of the main functions of the breathing tract is to ensure the air flow from the atmosphere and its removal from the human lungs.
Air purification from dust particles
Air is especially actively cleaned in the upper airway. Up to 90% of the dust particles contained in the air we breathe settle on their mucous membrane.
The smaller the particle, the greater the likelihood of its penetration into the lower airway. So, the bronchioles can reach particles with a diameter of 3-10 microns, and the alveoli – 1-3 microns.
The removal of dust particles is due to the mucus flow. This mucus covering the epithelium comes from the secretion of chalice cells and mucus-forming glands of the breathing tract, as well as the fluid filtered from the interstitium and haemocapillaries of the air tubes walls and also lungs.
This process occurs due to the contact of the inhaled air with the warm surface of the breathing tract. The efficiency of warming is such that even at inhale of a frosty atmospheric air, it heats up at the entry to the air tubes to a temperature of about 37 C. The air removed from the lungs gives up to 30% of its heat to the mucous membranes.
By flowing through air ways and alveoli, the breathing air is 100% saturated with water vapor. As a result, the pressure of water vapor in the alveolar air is about 47 mm Hg.