Which valve prevents backflow into the atrium when the ventricles contract?

Correct Answer: B

Rationale: The tricuspid valve (right atrioventricular valve) prevents backflow into the right atrium when the right ventricle contracts. This valve ensures that blood flows in the correct direction, preventing regurgitation into the atrium. The pulmonary valve is responsible for preventing backflow into the right ventricle from the pulmonary artery. The mitral valve prevents backflow into the left atrium, and the aortic valve prevents backflow into the left ventricle from the aorta. Therefore, the correct answer is the tricuspid valve as it specifically addresses the scenario of backflow into the atrium during ventricular contraction.

Correct Answer: A

Rationale: The correct answer is A: Right atrium, left atrium, right ventricle, left ventricle. The heart consists of four chambers: the right atrium, left atrium, right ventricle, and left ventricle. Blood flows from the body into the right atrium, then to the right ventricle, where it is pumped to the lungs for oxygenation. Oxygenated blood returns to the left atrium, passes to the left ventricle, and is then pumped out to the body. Choice B is incorrect because it incorrectly lists the left atrium twice. Choice C is incorrect as it rearranges the order of the chambers. Choice D is incorrect as it mistakenly switches the atria and ventricles in their positions.

Correct Answer: B

Rationale: The correct answer is B: Contraction of the heart. Systole is the phase of the cardiac cycle during which the heart muscle contracts, pumping blood out of the chambers. It is essential for maintaining circulation and delivering oxygen and nutrients to the body's tissues. Diastole (choice C) is the relaxation phase of the heart when the chambers fill with blood. Pulse rate (choice D) is the number of heartbeats per minute, not specifically related to the systole phase. Choice A, 'Relaxation of the heart,' is incorrect because systole refers to the contraction phase of the cardiac cycle, not relaxation.

Correct Answer: A

Rationale: The correct answer is A: Diastolic pressure. The bottom number in a blood pressure reading represents the diastolic pressure, which indicates the lowest pressure in the arteries when the heart is resting between beats. This value is important in understanding the overall health of the cardiovascular system. Choice B, Systolic pressure, is the top number in a blood pressure reading and represents the pressure in the arteries when the heart is contracting. Choice C, Pulse rate, refers to the number of times the heart beats in a minute. Choice D, Mean arterial pressure, is a calculated value using both systolic and diastolic pressures to provide an average pressure in the arteries during a cardiac cycle, but it is not the bottom number in a blood pressure reading.

Correct Answer: C

Rationale: The correct answer is C. Systemic circulation is longer as it involves carrying oxygenated blood throughout the body, requiring higher blood pressure. Pulmonary circulation is shorter and involves the flow of blood only through the lungs, hence having lower blood pressure. Therefore, systemic circulation is longer and has higher blood pressure compared to pulmonary circulation. Choice A is incorrect as systemic circulation is longer, not shorter, and has higher blood pressure. Choice B is incorrect as pulmonary circulation has lower blood pressure, not higher. Choice D is incorrect as systemic circulation is longer, not shorter, despite having higher blood pressure.