A medical patient rings her call bell and expresses alarm to the nurse, stating, 'I've just coughed up this blood. That can't be good, can it?' How can the nurse best determine whether the source of the blood was the patient's lungs?

Correct Answer: B

Rationale: The correct answer is B: Try to see if the blood is frothy or mixed with mucus. By observing if the blood is frothy or mixed with mucus, the nurse can determine if the source is more likely to be from the lungs, as blood from the lungs is often frothy due to air mixing with it during coughing. This observation helps differentiate between blood coming from the respiratory tract versus other sources in the body. Incorrect choices: A: Testing the pH of the blood does not directly indicate the source of the blood in this context. C: Performing oral suctioning may not provide accurate information about the source of the blood. D: Swabbing the back of the throat may not help determine if the blood is coming from the lungs as it could be from other sources in the upper respiratory tract.

Correct Answer: D

Rationale: The correct answer is D (more than 90). At a PO2 of 70 mm Hg, hemoglobin is more than 90% saturated with oxygen due to the high oxygen affinity of hemoglobin at this partial pressure. Hemoglobin exhibits near-maximal saturation at this level, promoting efficient oxygen binding and transport. Choices A, B, and C are incorrect as they do not accurately reflect the high oxygen saturation levels associated with a PO2 of 70 mm Hg.

Correct Answer: D

Rationale: The correct answer is D because the Hering-Breuer reflex is a protective mechanism that prevents lung damage from overinflation by inhibiting inspiration. When the lungs are at risk of overinflation, stretch receptors in the lung tissue send signals to the brainstem to reduce or stop inspiration, preventing excessive stretching of the alveoli. Choices A, B, and C are incorrect as the Hering-Breuer reflex is not involved in changes in blood pressure, PO2, or PCO2 regulation.

Correct Answer: D

Rationale: The correct answer is D because all the choices are structural features of the trachea. A is correct as the trachea has C-shaped cartilage rings for structural support. B is correct as the trachea contains smooth muscle fibers that help regulate airflow. C is correct as the trachea is lined with cilia that help sweep mucus and foreign particles out of the respiratory tract. Therefore, all of the above choices are structural features of the trachea, making D the correct answer.

Correct Answer: A

Rationale: The correct answer is A: alveoli. Alveoli are tiny air sacs in the lungs where gas exchange occurs. Oxygen from the air we breathe diffuses into the blood, and carbon dioxide from the blood diffuses into the alveoli to be exhaled. The pharynx, larynx, and trachea are parts of the respiratory system but do not participate in gaseous exchange. The pharynx serves as a passage for air and food, the larynx houses the vocal cords, and the trachea carries air to and from the lungs. Only the alveoli have the thin walls and large surface area necessary for efficient exchange of gases.