iGCSE Biology (0610)-9.1 Circulatory systems – iGCSE Style Questions Paper 1

Question

Which structures ensure the one-way flow of blood in the human circulatory system?

  1. alveoli

  2. capillaries

  3. synapses

  4. valves

    ▶️Answer/Explanation

    D

    The structures that ensure the one-way flow of blood in the human circulatory system are valves. Valves are present in certain blood vessels, primarily in the heart and veins, to prevent backflow of blood and maintain the desired direction of blood flow. There are four major valves in the human circulatory system:

    1. Aortic Valve: Located between the left ventricle and the aorta, this valve allows blood to flow from the heart’s left ventricle into the aorta, which carries oxygenated blood to the rest of the body.

    2. Pulmonary Valve: Situated between the right ventricle and the pulmonary artery, this valve permits blood to flow from the heart’s right ventricle into the pulmonary artery, which carries deoxygenated blood to the lungs for oxygenation.

    3. Tricuspid Valve: Found between the right atrium and the right ventricle, this valve allows blood to flow from the right atrium to the right ventricle during the relaxation phase of the heart.

    4. Mitral (Bicuspid) Valve: Located between the left atrium and the left ventricle, this valve permits blood to flow from the left atrium to the left ventricle during the relaxation phase of the heart.

    These valves open and close in response to pressure changes within the heart, ensuring that blood moves forward and does not flow backward, thus maintaining the one-way flow of blood through the circulatory system.

Question

Which diagram shows the human double circulatory system?

▶️Answer/Explanation

D

The human double circulatory system, as per diagram D, is the circulation of blood in two distinct pathways: the pulmonary circulation and the systemic circulation. It is a key feature of the cardiovascular system.

In the pulmonary circulation, deoxygenated blood is pumped from the right side of the heart to the lungs. This blood is low in oxygen and high in carbon dioxide, and it needs to be oxygenated and have carbon dioxide removed. In the lungs, the blood picks up oxygen and releases carbon dioxide through the process of respiration. Oxygenated blood then returns to the left side of the heart.

In the systemic circulation, oxygenated blood is pumped from the left side of the heart to the rest of the body. This oxygen-rich blood carries nutrients and oxygen to all the tissues and organs, delivering the necessary resources for their proper functioning. At the same time, it collects waste products, such as carbon dioxide and metabolic byproducts, and transports them away for elimination.

The double circulatory system ensures that oxygenated and deoxygenated blood remains separate, preventing the mixing of oxygen-rich and oxygen-poor blood. This efficient system allows for the effective delivery of oxygen and nutrients to tissues while facilitating the removal of waste products.

Overall, the human double circulatory system enables the continuous circulation of blood, maintaining the vital functions of oxygenation and nutrient supply throughout the body.

Question

What is the correct sequence for blood being pumped from the heart to the lungs?

A    left atrium → left ventricle → pulmonary artery
B    left atrium → left ventricle → pulmonary vein
C    right atrium → right ventricle → pulmonary artery
D   right atrium → right ventricle → pulmonary vein

▶️Answer/Explanation

C

The correct sequence for blood being pumped from the heart to the lungs is:

C. right atrium → right ventricle → pulmonary artery

Blood returns from the body to the right atrium of the heart. From the right atrium, it passes through the tricuspid valve into the right ventricle. The right ventricle then pumps the blood into the pulmonary artery, which carries the deoxygenated blood to the lungs for oxygenation.

 

Question

Why is the circulatory system of mammals described as a double circulation?

A    Blood flows firstly through arteries and then through veins.
B    Blood flows through the heart twice on one complete circuit of the body.
C    In the heart, blood flows firstly through atria and then through ventricles.
D    The atria and the ventricles contract alternately.

▶️Answer/Explanation

B

The correct answer is B: Blood flows through the heart twice on one complete circuit of the body.

The circulatory system of mammals is described as a double circulation because blood passes through the heart twice during one complete circuit of the body. This means that there are two distinct pathways for blood flow: one for oxygenated blood and another for deoxygenated blood.

The process begins with oxygenated blood being pumped from the lungs into the left atrium of the heart. From there, it is pumped into the left ventricle, which then contracts to push the oxygenated blood out through the aorta and into the systemic circulation. In the systemic circulation, the oxygenated blood delivers oxygen and nutrients to the body tissues.

After the oxygen is used up and the blood becomes deoxygenated, it returns to the heart through the superior and inferior vena cava, entering the right atrium. From the right atrium, the blood moves into the right ventricle, which contracts to pump the deoxygenated blood out through the pulmonary artery and into the lungs. In the lungs, the blood picks up fresh oxygen and releases carbon dioxide, becoming oxygenated once again.

The oxygenated blood then returns to the heart through the pulmonary veins, entering the left atrium and completing the double circulation cycle.

So, the double circulation in mammals involves the movement of blood from the heart to the lungs and back (pulmonary circulation) and from the heart to the rest of the body and back (systemic circulation).

Question

The diagram shows a double circulatory system.

Which vessels carry oxygenated blood?
A  1 and 2                  1 and 4                    C  2 and 3                2 and 4

▶️Answer/Explanation

D

In a diagram of the double circulatory system, the vessels that carry oxygenated blood are: 2 and 4

1. Pulmonary Veins: These vessels carry oxygenated blood from the lungs back to the heart. In the pulmonary circulation, blood is oxygenated in the lungs, and the oxygen-rich blood returns to the heart through the pulmonary veins.

2. Systemic Arteries: After the oxygenated blood leaves the heart through the left ventricle, it is pumped into the systemic circulation through the systemic arteries. These arteries distribute the oxygenated blood to various organs and tissues throughout the body.

The double circulatory system consists of two distinct circuits: the pulmonary circulation and the systemic circulation. The pulmonary circulation deals with the exchange of gases (oxygen and carbon dioxide) between the lungs and the blood, while the systemic circulation delivers oxygenated blood to the body’s tissues and carries deoxygenated blood back to the heart.

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