The hemoglobin oxygen saturation of blood entering the right atrium is about:

Correct Answer: C

Rationale: Venous blood in the right atrium has ~75% O₂ saturation (C, SvO₂) after systemic use (~25% extracted). A, B, and D underestimate normal values.

Correct Answer: C

Rationale: Increased stroke volume occurs with increased preload (more filling), decreased afterload (less resistance), and increased contractility (stronger contraction, C). Other combinations counteract.

Correct Answer: B

Rationale: The left ventricle pumps blood through the aortic semilunar valve (B) into the aorta during systole. Mitral (A) is inflow, pulmonary (C) is right-sided, tricuspid (D) is right AV.

Correct Answer: C

Rationale: The myocardium (C) is the muscular layer responsible for contraction. Endocardium (A) is inner, epicardium (B) is outer, pericardium (D) is the sac.

Correct Answer: C

Rationale: Blood temperature is ~100.4°F (A) and pH is 7.35-7.45 (B), but it’s red due to erythrocytes/hemoglobin, not leukocytes (C). Volume is ~5L (D).