The sympathetic nervous system will______ contraction strength of the heart, thus leading to a(n) ______ in stroke volume.

Correct Answer: C

Rationale: Sympathetic stimulation increases the force of cardiac contraction, thereby increasing stroke volume.

Correct Answer: C

Rationale: The renal veins drain blood from the kidneys.

Correct Answer: C

Rationale: The pulmonary semilunar valve is located at the base of the pulmonary trunk and prevents backflow of blood into the right ventricle after contraction.

Correct Answer: D

Rationale: The left ventricle has the thickest myocardium because it must generate sufficient force to pump blood throughout the entire body via the systemic circulation.

Correct Answer: A

Rationale: Fetal circulation includes two umbilical arteries and one umbilical vein.