Why is most food digested?

Correct Answer: C

Rationale: The correct answer is C because most ingested food molecules are large and need to be broken down into smaller molecules for absorption. Digestion involves the breakdown of complex nutrients into simpler forms that can be absorbed by the body. Choice A is incorrect because digestive enzymes can work on a variety of substrates, not necessarily requiring a variety. Choice B is incorrect as digestion is not primarily aimed at balancing the diet but rather extracting nutrients. Choice D is incorrect as digestion primarily occurs in the stomach and small intestine, not specifically to prevent disorders of the intestine.

Correct Answer: A

Rationale: The correct answer is A: esophagus. The esophagus is a muscular tube that carries food from the mouth to the stomach through a process called peristalsis. It is lined with muscles that contract to push food downward. The trachea (B) is responsible for breathing, not digestion. The nasopharynx (C) is part of the respiratory system. The epiglottis (D) is a flap of tissue that prevents food from entering the trachea during swallowing.

Correct Answer: B

Rationale: The most likely diagnosis for the given presentation is Gastro-oesophageal reflux disease (GERD). The chest pain exacerbated by lying flat and relieved by leaning forward is typical of GERD due to acid reflux when lying down. Angina and myocardial infarction typically present with exertional chest pain, while pulmonary embolism presents with sudden onset pleuritic chest pain often associated with shortness of breath. Therefore, the correct answer is B.

Correct Answer: D

Rationale: The correct answer is D: Right heart failure. The swollen ankles and raised jugular venous pressure are consistent with right heart failure in the setting of chronic obstructive pulmonary disease. In COPD, chronic hypoxia can lead to pulmonary hypertension and subsequent right heart failure. Asthma (choice A) is a reversible airway disease, not associated with right heart failure. Congestive heart failure (choice B) typically presents with features of pulmonary edema, which are absent in this case. Constrictive pericarditis (choice C) can also cause elevated jugular venous pressure, but swollen ankles are not a common feature.

Correct Answer: A

Rationale: The correct answer is A: Right-sided heart failure secondary to lung disease. In cor pulmonale, chronic lung disease such as COPD leads to pulmonary hypertension, which in turn causes the right side of the heart to work harder and eventually fail. This is because the right side of the heart pumps blood to the lungs to pick up oxygen, and when the lungs are diseased, the heart has to pump harder to maintain adequate blood flow. Choices B, C, and D are incorrect because they do not accurately describe cor pulmonale. Left-sided heart failure (choice B) is not directly related to lung disease, whereas lung disease secondary to left-sided heart failure (choice C) and lung disease secondary to right-sided heart failure (choice D) are not accurate descriptions of cor pulmonale.