Every time you take a breath, you are (1) _____ the respiratory surfaces of your lungs. Each lung has approximately 300 million tiny thin-walled outpouching air sacs called (2) ____.
Inhaled air dead-ends in these (2), each of which is surrounded by a network of pulmonary (3) _______ into which oxygen from air diffuses and is exchanged for (4) ___ ___ waste gases diffusing from the bloodstream into alveolar cavities.
The (5) ____ _____ surrounds each lung. In succession, air passes through the nasal cavities, pharynx, and (6) _____, past the epiglottis into the (7) ______ (the space between the true vocal cords), into the trachea, and then to the (8) _____, (9) _____, and alveolar ducts. Exchange of gases occurs across the epithelium of the (10)______.
In addition to gas exchange, breathing has other functions, such as ridding the body of excess heat and water vapor, adjusting the body's acid-base balance, and producing (11) ____ to communicate with other creatures.
A. pleural membrane
J. carbon dioxide
During inhalation, the (1) _____ moves downward and flattens, and the (2) ____ moves outward and upward. When these things happen, the chest cavity volume (3) _______ and the internal pressure (4)_____.
When the thoracic (chest) cavity expands during inhalation, the lungs must expand too because water molecules in the (5) _____ fluid are cohesive and behave like a "glue" binding the lungs to the thoracic wall. With active expiration (breathing out), the muscles in the abdominal wall contract, and pressure is exerted upward on the (6) _____, decreasing the volume of the chest cavity. The internal (7) _____ muscles also contract, pulling the chest wall downward and inward and further decreasing the volume of the chest cavity. Internal pressure (8) _____ and flows up the airways and outward because pressure in the alveoli is (9) _____ than the atmospheric pressure.
Quite exhalation is (10) _____; the muscles relax and the lungs recoil without any further energy outlays after an inhalation.
(11) _________ is the distension of lungs and the loss of gas exchange efficiency such that running, walking, and even exhaling are painful experiences. At least 90 percent of all (12) ____ ____ deaths are the result of cigarette smoking; only about 10 percent of afflicted individuals will survive.
G. rib cage
I. lung cancer
1. c (ventilating)
2. e (alveoli)
3. g (capillaries)
4. j (carbon dioxide)
5. a (pleural ...