Which of the following infections can be diagnosed using a skin test similar to the tuberculin test?

Correct Answer: A

Rationale: Histoplasmosis can be diagnosed with a skin test like the tuberculin test, using histoplasmin to trigger a delayed hypersensitivity reaction in exposed individuals, indicating past or latent infection common in endemic areas like the Mississippi Valley. Cryptococcosis relies on antigen detection or culture, not skin tests, due to its yeast nature and immunocompromised host focus. Blastomycosis lacks a reliable skin test diagnosis uses microscopy or culture. Aspergillosis, an opportunistic mold infection, uses imaging and biopsy, not skin reactivity. The histoplasmosis test, though less common now due to serology's rise, parallels tuberculosis's immune-based detection, aiding epidemiology and distinguishing it from other fungal respiratory diseases.

Correct Answer: C

Rationale: The mediastinum, the central thoracic compartment between the pleural sacs, houses the heart, great vessels, trachea, and esophagus, extending from the sternum to the vertebral column. The hilum is the lung's entry point for vessels and bronchi, not a compartment. Pleura are the lung linings, not a central space. The thoracic cage (ribs, sternum, spine) encases the chest, not a specific region. The mediastinum's role as a structural and functional core separating lungs while supporting vital organs makes it distinct, critical in anatomy for understanding thoracic pathology like mediastinal masses or infections affecting central structures.

Correct Answer: B

Rationale: The trachea filters air we breathe, lined with cilia and mucus that trap dust and microbes, preventing lung entry part of the mucociliary escalator. Gaseous exchange occurs in alveoli, not the trachea, which only conducts air. Exhalation is a lung-diaphragm action; the trachea is a passive conduit. 'All' is wrong filtering is its sole listed role. This protective function, supported by C-shaped cartilage keeping it open, ensures clean air reaches the lungs, critical for respiratory health, distinct from exchange or expulsion processes, a key anatomical distinction in airway mechanics.

Correct Answer: C

Rationale: The fibrous pericardium, the pericardium's outermost layer, is inelastic dense irregular connective tissue, anchoring the heart to the diaphragm and sternum, preventing overstretch. The parietal layer is serous, lining the fibrous part, not the outer tissue. Serous pericardium includes parietal and visceral (epicardium) layers, both thin and lubricative. The epicardium is the heart's surface, not pericardial. This tough fibrous layer's protective rigidity contrasts with the serous layers' fluidity, a structural balance critical for heart stability, key in understanding pericardial anatomy and conditions like constrictive pericarditis.

Correct Answer: D

Rationale: Atrial contraction (atrial systole) pushes blood through atrioventricular valves tricuspid to the right ventricle, mitral to the left topping off ventricular filling before systole. Auricles are atrial extensions, not destinations. Arteries receive blood from ventricles, not atria. Veins deliver to atria, not from them. This valve passage, late in diastole, boosts ventricular volume by 20-30%, enhancing stroke volume, a subtle but vital step in the cardiac cycle, critical in understanding preload and atrial contribution to heart efficiency.