The nurse doing rounds at the beginning of a shift notices a sputum specimen in a container sitting on the bedside table in a patient's room. The nurse asks the patient when he produced the sputum specimen and he states that the specimen is about 4 hours old. What action should the nurse take?

Correct Answer: B

Rationale: The correct answer is B: Discard the specimen and assist the patient in obtaining another specimen. It is important to discard the sputum specimen because it has been sitting for 4 hours, which could lead to contamination and inaccurate test results. The nurse should assist the patient in obtaining a fresh specimen to ensure accurate testing. Choice A is incorrect because taking the old specimen to the lab could lead to inaccurate results. Choice C is incorrect because refrigerating the old specimen won't prevent contamination. Choice D is incorrect because adding saline to the old specimen can alter its composition and lead to inaccurate test results.

Correct Answer: D

Rationale: The correct answer is D: anatomic dead space. Anatomic dead space refers to the air in the conducting passages (such as trachea, bronchi) that does not reach the alveoli for gas exchange. This space only serves as a pathway for air to move in and out of the lungs. Vital capacity (A) is the maximum amount of air that can be exhaled after a maximum inhalation. Minimal volume (B) is not a recognized term in respiratory physiology. Residual volume (C) is the amount of air left in the lungs after a maximal exhalation and is not specifically related to the air in conducting passages.

Correct Answer: A

Rationale: The correct answer is A, during external respiration. Oxyhemoglobin forms when oxygen binds to hemoglobin in the lungs during external respiration. This process occurs in the alveoli where oxygen diffuses from the air sacs into the blood, binding with hemoglobin to form oxyhemoglobin. Choices B, C, and D are incorrect because oxyhemoglobin formation specifically happens during external respiration, not immediately after carbon dioxide enters the blood, when the chloride shift occurs, or during pulmonary ventilation. These processes are important in respiration but do not directly involve the formation of oxyhemoglobin.

Correct Answer: B

Rationale: The correct answer is B: the precentral motor gyrus. This area is primarily responsible for voluntary motor control, not for altering the activity of respiratory centers. Cortical association areas (A), the limbic system (C), and the hypothalamus (D) can influence respiratory centers through emotional responses, autonomic control, and regulation of breathing patterns, respectively. The precentral motor gyrus is not directly involved in modifying respiratory activity.

Correct Answer: D

Rationale: The correct answer is D: oral cavity. The fauces is the opening between the oral cavity and the oropharynx. It is located at the back of the mouth, connecting the oral cavity to the oropharynx. This opening allows the passage of food and liquids from the mouth to the throat during swallowing. Choices A, B, and C are incorrect because the fauces does not connect to the nasopharynx, laryngopharynx, or nasal cavity. The fauces specifically connects the oral cavity to the oropharynx, making choice D the correct answer in this context.