The outermost of the three layers of the heart is the:

Correct Answer: A

Rationale: The heart has three layers: endocardium (inner), myocardium (middle), and epicardium (outer). The epicardium is the outermost layer of the heart wall itself, while the pericardium is a separate sac surrounding the heart. 'Supracardium' is not a real term.

Correct Answer: B

Rationale: At the arteriolar end, high hydrostatic pressure pushes oxygen and nutrients out; at the venular end, lower pressure allows wastes to enter via diffusion and osmosis. Capillary density correlates positively with metabolism, and arrangements vary by tissue.

Correct Answer: B

Rationale: The S₂ heart sound ('dub') is produced by the closure of the aortic and pulmonic valves. A murmur at S₂ suggests impairment of one of these, most likely the aortic valve, as it’s more commonly affected in adults (e.g., stenosis). Tricuspid and mitral (bicuspid) closure produces S₁. (Source: Document, p. 62, Valve sounds)

Correct Answer: C

Rationale: Calcium ions are essential in the clotting cascade, particularly for converting prothrombin to thrombin (via factor Xa). They also aid other steps but are not directly needed to form fibrinogen, thromboplastin, or prothrombin.

Correct Answer: B

Rationale: IgE is primarily involved in allergic reactions and parasitic infections, binding to mast cells and basophils to release histamine. IgG protects newborns via placental transfer, IgA protects mucosal areas, and IgM fights bacteria.