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Free Circulation MCQs with Answers

695 Circulation MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

The circulatory system covers the chambers, valves and conducting pathway of the human heart, along with the cardiac cycle and control of heartbeat. It compares arteries, veins and capillaries by structure and function, and explains how the lymphatic system returns tissue fluid, transports absorbed fats and supports immunity.

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Human HeartCardiac Cycle and HeartbeatBlood VesselsLymphatic System
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695 questions · page 35 of 35

681. The interval of pacemaker signals from S.A.N to A.V.N is:

  • A. 1 second
  • B. 0.1 second
  • C. 2 seconds
  • D. 0.2 second

Explanation: The sinoatrial node (SAN) initiates the heartbeat and sends signals to the atrioventricular node (AVN) with a delay of about 0.1 second.

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Correct answer: 0.1 second

682. In E.C.G QRS complex represent:

  • A. Atrial systole
  • B. Atrial diastole
  • C. Ventricle systole
  • D. Ventricle diastole

Explanation: The second part of ECG is the QRS complex which features a small drop in voltage (Q) a large voltage peak ( R ) and another small drop in…

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Correct answer: Ventricle systole

683. The Purkinje fibers are the specialized fibers found in:

  • A. Human heart
  • B. Human lungs
  • C. Human stomach
  • D. Human brain

Explanation: Option A is correct.The Purkinje fibers are the specialized fibers found in the human heart.

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Correct answer: Human heart

684. The opening between right atrium and right ventricle is guarded by

  • A. semi lunar valve
  • B. tricuspid valve
  • C. bicuspid valve
  • D. semicircular valve

Explanation: The opening between the right atrium and right ventricle is guarded by the tricuspid valve.

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Correct answer: tricuspid valve

685. In fishes, the heart pumps:

  • A. Pure blood to body
  • B. Impure blood to body
  • C. Pure blood to gills
  • D. Impure blood to gills

Explanation: In fishes, the heart pumps out deoxygenated blood from the body to the gills where it gets oxygenated.

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Correct answer: Impure blood to gills

686. The valve between left atrium and left ventricle is :

  • A. Semi lunar valve
  • B. Tricuspid valve
  • C. Pulmonary valve
  • D. Bicuspid valve

Explanation: The bicuspid valve, also known as the mitral valve, is the correct answer because it is located between the left atrium and left…

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Correct answer: Bicuspid valve

687. Heart muscles are called:

  • A. Smooth muscles
  • B. Myogenic muscles
  • C. Striated muscles
  • D. Skeletal muscles

Explanation: The heart muscles are called myogenic muscles because they can contract on their own without direct nerve stimulation.

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Correct answer: Myogenic muscles

688. The valves between the right atrium and right ventricle is called:

  • A. bicuspid valve
  • B. tricuspid valve
  • C. pulmonary valve
  • D. semi lunar valve-

Explanation: The valve between the right atrium and the right ventricle is the tricuspid valve.

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Correct answer: tricuspid valve

689. The valve between left ventricle and aorta is called:

  • A. Semi lunar valve
  • B. Blcuspid valve
  • C. Tricuspid valve
  • D. Pulmonary valve

Explanation: The term semilunar refers to the aortic valve and the pulmonary valve, tricuspid is the valve between the right atrium and ventricular and…

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Correct answer: Semi lunar valve

690. The possible reason(s) for cyanosis, one of congenital heart disease is:

  • A. Formation of carboxy-hemoglobin
  • B. The high concentration of oxyhemoglobin
  • C. Low level of carbon monoxide (CO)
  • D. Low level of hemoglobin

Explanation: The correct answer is the formation of carboxy-hemoglobin. This occurs when carbon monoxide binds to hemoglobin with a much higher…

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Correct answer: Formation of carboxy-hemoglobin

691. The normal systolic B P of aorta is _

  • A. 60 mm Hg
  • B. 120 mm Hg
  • C. 80 mm Hg
  • D. 102 mm Hg

Explanation: So, when we talk about the normal systolic blood pressure of the aorta, we're referring to the pressure in the main artery of the body…

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Correct answer: 120 mm Hg

692. In human heart's right atrium communicates with the right ventricle through:

  • A. Inter-auricular septum
  • B. Ventricular septum
  • C. Tricuspid valve
  • D. Bicuspid valve

Explanation: Option C is correct.In the human heart, the right atrium communicates with the right ventricle through the tricuspid valve.

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Correct answer: Tricuspid valve

693. The sinoatrial node is located in the _ wall of the right atrium.

  • A. Lower dorsal
  • B. Upper dorsal
  • C. On the interatrial septum
  • D. Near the coronary sinus

Explanation: The sinoatrial (SA) node, also known as the natural pacemaker, is located in the upper dorsal (posterior) wall of the right atrium, near…

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Correct answer: Upper dorsal

694. The largest lymphatic duct is the:

  • A. Abdominal duct
  • B. Thoracic duct
  • C. Femoral duct
  • D. Subclavian duct

Explanation: The thoracic duct is the largest lymphatic duct in the body. It collects lymph from most of the body (except the right arm and right side…

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Correct answer: Thoracic duct

695. The largest body of lymphoid tissue in the human body is:

  • A. Tonsils
  • B. Pancreas
  • C. Spleen
  • D. Thymus

Explanation: Option C is correct.The largest body of lymphoid tissue in the human body is the spleen.

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Correct answer: Spleen
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