(A) The partial pressure in the lungs is higher than in the blood, and oxygen diffuses out of the lungs passively.

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Joshua Watkins
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1 DAT Biology - Problem Drill 12: The Respiratory System Question No. 1 of Which statement about the partial pressure of oxygen inside the lungs is correct? Question #01 (A) The partial pressure in the lungs is higher than in the blood, and oxygen diffuses out of the lungs passively. (B) The partial pressure in the lungs is lower than in the blood, and oxygen diffuses out of the lungs passively. (C) The partial pressure in the lungs is higher than in the blood, and the carbon dioxide partial pressure in the lungs is equal with the blood. (D) The partial pressure in the lungs is higher than in the blood, and oxygen is actively transported to an area of higher concentration. (E) None of the above A. Correct! The partial pressure in the lungs is higher than in the blood, so the oxygen diffuses out of the lungs passively. The partial pressure in the lungs is higher than in the blood. The carbon dioxide partial pressure in the lungs is lower than in the blood. Oxygen diffuses passively into the blood and moves towards an area of lower concentration. There is one correct answer above. Oxygen and carbon dioxide exchange passively between the pulmonary capillaries and the alveoli. These gases move along their partial pressure gradients, i.e.- from high to low. The partial pressure of oxygen is higher in the lungs. Therefore, oxygen moves along its pressure gradient from the lung into the blood. The partial pressure of carbon dioxide is higher in the blood. Therefore, carbon dioxide moves along its pressure gradient from blood into the lungs to be exhaled. The correct answer is (A).

2 Question No. 2 of The blood entering the pulmonary capillaries has (prior to gas exchange)? Question #02 (A) Higher partial pressure of oxygen than when it leaves the lungs. (B) Lower partial pressure of oxygen than when it leaves the lungs. (C) Lower partial pressure of carbon dioxide than when it leaves the lungs. (D) The same partial pressure of oxygen when it leaves the lungs. (E) The same partial pressure of carbon dioxide when it leaves the lungs. The blood has lower partial pressure of oxygen than when it leaves the lungs. B. Correct! The blood has lower partial pressure of oxygen than when it leaves the lungs. The blood has higher partial pressure of carbon dioxide than when it leaves the lungs. Initially, the partial pressure of oxygen in the blood is low and after gas exchange it increases. This causes the partial pressure of oxygen to be higher when it leaves the lungs. The blood has lower partial pressure of oxygen than when it leaves the lungs. Initially, the partial pressure of oxygen is low, but after gas exchange it increases. This causes the partial pressure of oxygen to be higher when it leaves the lungs. When the blood enters the pulmonary capillaries PO 2 = 40 mmhg and PCO 2 = 45 mmhg. After gas exchange, PO 2 = 100 mmhg and PCO 2 = 40 mmhg. The correct answer is (B).

3 Question No. 3 of What are two methods the respiratory system uses to protect the body from foreign particles and pathogens? Question #03 (A) Traps foreign particles and pathogens in the mucous of the lungs and stores it in the lungs. (B) Traps foreign bodies and pathogens in the mucous of the lungs and moves it towards the mouth to be swallowed and removed/destroyed by the gastrointestinal tract. (C) Alveolar macrophages phagocitize foreign bodies and pathogens and release them back into the alveoli for removal during exhalation. (D) Alveolar macrophages phagocitize foreign bodies and pathogens that only leave the lungs in the ascending layer of mucous. (E) None of the above The trapped foreign particles and pathogens are not stored in the lungs. B. Correct! The respiratory system traps foreign bodies and pathogens in the mucous of the lungs and moves it towards the mouth to be swallowed and removed/destroyed by the gastrointestinal tract. Alveolar macrophages phagocitize foreign bodies and pathogens, but remove them from the lungs. Alveolar macrophages phagocitize foreign bodies and pathogens that either leave the lungs in the ascending layer of mucous or through the alveolar lymphatic system. There is one correct answer above. The respiratory system protects the human body from foreign particles and pathogens by (a) trapping foreign bodies and pathogens in the mucous of the lungs and moving the trapped particles towards the mouth to be swallowed and removed/destroyed by the gastrointestinal tract, or (b) through alveolar macrophages that phagocitize foreign bodies and pathogens that then either leave the lungs in the ascending layer of mucous or through the alveolar lymphatic system. The correct answer is (B).

4 Question No. 4 of Which of the following statements about the respiratory system s involvement in thermoregulation is correct? Question #04 (A) The inspired air is heated in the lungs to the internal body temperature of 37ºC and humidified to 100%. (B) The inspired air is heated in the lungs to the internal body temperature of 30ºC and is humidified to 100%. (C) During exhalation the expired air is cooled to 20ºC. (D) The temperature of air in the lungs is similar to the temperature of the air in the external environment, throughout the breathing cycle. (E) None of the above A. Correct! The inspired air is heated in the lungs to the internal body temperature of 37ºC and is humidified to 100%. The inspired air is heated in the lungs to the internal body temperature of 37ºC. Expired air is about 30ºC. Inspired air is heated or cooled to the internal body temperature. There is one correct answer above. During inhalation, room temperature air is brought into the respiratory system and heated or cooled to internal body temperature (37ºC, 100% humidity). Air in the lungs, below the trachea, is ~37ºC and 100% humidified. During exhalation, expired gas is 100% humidified and about 30ºC. Therefore, if you are breathing in a room where the external environment is 20ºC and you are exhaling air from the lungs that is about 30ºC, there is a net heat loss to the environment. The correct answer is (A).

5 Question No. 5 of Which of the following statements about respiratory mechanics is correct? Question #05 (A) During quiet breathing the diaphragm contracts and returns to its preinhalation position through active processes. (B) Breathing is an active and passive process under involuntary control only. (C) During quiet breathing the diaphragm actively contracts and returns to its pre-inhalation position passively. (D) During exhalation the chest wall expands and the diaphragm contracts. (E) During quiet breathing the diaphragm remains at the same position. During quiet breathing the diaphragm contracts and returns to its pre-inhalation position passively. Breathing is under voluntary and involuntary control. C. Correct! During quiet breathing the diaphragm actively contracts and returns to its preinhalation position passively. During inhalation the chest wall expands and the diaphragm contracts. No, it does not. During quiet breathing the diaphragm actively contracts and returns to its pre-inhalation position passively. Breathing is an active process of muscle activity, under voluntary and involuntary control. During quiet breathing, the diaphragm is the major muscle involved in the breathing cycle. During inhalation the chest wall expands and the diaphragm contracts. During exhalation the diaphragm relaxes to its pre-inhalation position passively. The correct answer is (C).

6 Question No. 6 of Which of the statements best describes the pressure inside of the lungs during the breathing cycle? Question #06 (A) Less than the atmospheric pressure at the end of exhalation, just before the beginning of inhalation. (B) When the diaphragm actively contracts at the beginning of inhalation, the internal lung volume decreases and the internal pressure inside the lung increases. (C) When the diaphragm actively contracts at the beginning of inhalation, the internal lung volume decreases and the internal pressure inside the lung decreases. (D) At the end of inhalation the diaphragm relaxes passively, and this causes the internal lung volume to increase and the internal lung pressure to decrease. (E) All of the above The pressure in the lungs is the same as the atmospheric pressure at the end of exhalation, just before the beginning of inhalation. When the diaphragm actively contracts at the beginning of inhalation, the internal lung volume decreases and the internal pressure inside the lung decreases. C. Correct! When the diaphragm actively contracts at the beginning of inhalation the internal lung volume increases and the internal pressure inside the lung decreases. At the end of inhalation the diaphragm relaxes passively, this causes the internal lung volume to decrease and the internal lung pressure to increase. Not all, but just one correct statement. At the end of exhalation, just before the beginning of inhalation, the pressure inside the lung is the same as the atmospheric pressure outside the body. When the diaphragm actively contracts, the internal lung volume increases and the pressure inside the lung decreases. The change in internal pressure causes air to rush into the lungs and down its pressure gradient. At the end of inhalation, the diaphragm relaxes passively. The lung volume decreases and this causes the internal pressure inside the lungs to increase to a level higher than atmospheric pressure outside the body. This causes air to exit the lung, down its pressure gradient. The correct answer is (C).

7 Question No. 7 of Which of the following statements about the physical properties of the lungs is correct? Question #07 (A) The elastic fibers in the walls of the alveoli allow the lungs to expand during exhalation. (B) Elastins are elastic fibers present in the upper airways. (C) Lung compliance is the dispensability of the elastic lungs and corresponds to the ability of the lungs to expand during inhalation. (D) As the volume in the lung decreases the lung compliance decreases. (E) Lung compliance has nothing to do with its ability to expand during inhalation. The elastic fibers in the walls of the alveoli allow the lungs to recoil during exhalation. Elastins are elastic fibers present in walls of the alveoli. C. Correct! Lung compliance is the dispensability of the elastic lungs and corresponds to the ability of the lungs to expand during inhalation. As the volume in the lung decreases the lung compliance increases. Not true. Lung compliance is the dispensability of the elastic lungs and corresponds to the ability of the lungs to expand during inhalation. Lung elasticity is the ability of the lungs elastic tissue to recoil during exhalation. Elastins are elastic fibers present in the walls of the alveoli, which allow the lungs to return to their resting volume after exhalation. Lung compliance is the volume change per unit of pressure across the lungs. In other words, it is the dispensability of the elastic lungs and corresponds to the ability of the lungs to expand during inhalation.. The correct answer is (C).

8 Question No. 8 of Which statement best describes surface tension. Question #08 (A) It s the attraction of liquid molecules in the surface layer of a liquid inward towards each other. (B) It s the attraction of liquid molecules in the surface layer of a liquid outward away from each other. (C) It has no role in the respiratory system. (D) It prevents the surface layer from behaving like an elastic sheet. (E) It expels the molecules on the surface. A. Correct! Surface tension is the attraction of liquid molecules in the surface layer of a liquid inward towards each other. Surface tension is the attraction of liquid molecules in the surface layer of a liquid, but not in this direction. Surface tension acts at the air water interface to make the alveoli shrink. Surface tension causes that surface layer to behave like an elastic sheet. No, it does not expel, rather it is the attraction of liquid molecules. Surface tension is the attraction of liquid molecules in the surface layer of a liquid inward towards each other. This causes that layer to behave like an elastic sheet. Surface tension in the case of the lung causes the alveoli to shrink. The correct answer is (A).

9 Question No. 9 of Which of the following statements about pulmonary surfactant is correct? Question #09 (A) Pulmonary surfactant is a phospholipid, similar to those found in the lipid bilayer surrounding human cells. It is made by macrophages in the lungs. (B) Pulmonary surfactant has two components: (A) a nonpolar (water fearing) head, and (B) a polar (water loving) tail. (C) Pulmonary surfactant has two components: (A) a polar (water loving) head, and (B) a nonpolar (water fearing) tail. (D) Pulmonary surfactant is a protein, similar to those found in the lipid bilayer surrounding human cells. (E) Pulmonary surfactant has two components: (A) a polar (water loving) head, and (B) a polar (water loving) tail. Pulmonary surfactant is made by pneumocytes in the lungs. The head of the pulmonary surfactant is not nonpolar. C. Correct! Pulmonary surfactant has two components: (A) a polar (water loving) head, and (B) a nonpolar (water fearing) tail. Pulmonary surfactant is a phospholipid, similar to those found in a lipid bilayer surrounding human cells. It has one polar head and one nonpolar tail. Pulmonary surfactant is a phospholipid, similar to those found in a lipid bilayer surrounding human cells. It is made by pneumocytes in the lungs. Pulmonary surfactant has two components: (A) a polar (water loving) head, and (B) a nonpolar (water fearing) tail. The correct answer is (C).

10 Question No. 10 of Which of the following statement about pulmonary surfactant s role in the lungs is correct?. (A) Pulmonary surfactant is adsorbed into the liquid layer on the alveoli, which increases surface tension. (B) The surfactant polar tail is adsorbed into the liquid/water covering of the alveoli. (C) Surfactant is adsorbed into the liquid layer on the alveoli, which increases Question #10 surface tension and decreases lung compliance. (D) Pulmonary surfactant is adsorbed into the liquid layer on the alveoli, which decreases surface tension. (E) Pulmonary surfactant is adsorbed into the liquid layer on the alveoli, which keeps the same surface tension. Pulmonary surfactant is adsorbed into the liquid layer on the alveoli, which decreases surface tension. The surfactant polar head is adsorbed into the liquid/water covering of the alveoli. Surfactant is adsorbed into the liquid layer on the alveoli, which decreases surface tension and increases lung compliance. D. Correct! Pulmonary surfactant is adsorbed into the liquid layer on the alveoli, which decreases surface tension. Pulmonary surfactant is adsorbed into the liquid layer on the alveoli, which decreases surface tension. If the alveoli in the lung are compared to an air bubble in water then (a) both are wet and surround a pocket of air, and (b) surface tension acts at the air-water interface to make the bubble smaller, or in the case of the lung, the alveoli to shrink. The surfactant polar head is absorbed into the liquid/water covering of the alveoli. The surfactant nonpolar tail faces towards the air inside the alveoli. Surfactant that is adsorbed into the liquid layer on the alveoli decreases surface tension. This increases lung compliance and makes the lungs easier to inflate, as well as preventing the lungs from collapsing at the end of exhalation. The correct answer is (D).

Respiratory System. Part 2

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