The stroke output of each ventricle in normal adult is:

Correct Answer: C

Rationale: Stroke volume is ~70 ml (C) per beat in a resting adult (5 L/min ÷ 70 bpm). 30 ml (A) is too low, 130 ml (B) too high, and 5 L (D) is cardiac output.

Correct Answer: A

Rationale: Both circulations handle the full cardiac output (~5 L/min, A). Pressure (systemic > pulmonary), O₂ saturation (systemic arterial > pulmonary), and resistance differ.

Correct Answer: C

Rationale: Gap junctions (C) electrically connect cardiac muscle fibers, allowing synchronized contraction. Desmosomes (A) provide mechanical strength, tight junctions (B) are rare, and interneurons (D) are neural.

Correct Answer: D

Rationale: Cardiac reserve (D) is the difference between maximum and resting cardiac output, reflecting heart capacity.

Correct Answer: B

Rationale: The mitral valve (B) opens into the left ventricle from the left atrium during diastole. Aortic (A) is outflow, tricuspid (C) and pulmonary (D) are right-sided.