The circulatory system

Question 1

The liquid part of the blood called plasma carries a number of important substances around the body:

Answer 1

• Dissolved food substances such as glucose
• Carbon dioxide from the tissues to the lungs
• Hormones from the glands where they are made, to their target cells
• Plasma proteins such as antibodies
• Waste substances such as urea

Question 2

Red blood cells are adapted to their function of carrying oxygen in a number of ways:

Answer 2

• They are very small so that they can pass through the smallest blood vessels.
• They are shaped like bioconcave discs so that they have a large surface area to exchange oxygen quicker.
• They contain haemoglobin to combine with oxygen. It is the haemoglobin that makes them appear red.
• They don’t have a nucleus so more haemoglobin can fit.

Question 3

What does the shape of blood cells do?

Answer 3

The biconcave shape of the red blood cell provides a larger surface area to volume ratio to exchange oxygen more quickly.

Question 4

How does haemoglobin react with oxygen?

Answer 4

• Haemoglobin in red blood cells reacts with oxygen in the lungs, forming oxyhaemoglobin.
• The reaction is reversible: when the oxyhaemoglobin reaches the tissues, the oxygen is released.

Question 5

The different types of blood vessels have different jobs:

Answer 5

• Arteries transport blood away from the heart to the tissues.
• Veins transport blood back to the heart from the tissue.
• Capillaries link arteries to veins and allow materials to pass between the blood and the tissues.

Question 6

The structures of arteries, veins and capillaries are adapted to carry out specific functions:

Answer 6

• Arteries have a thick muscular and elestic wall to resist the high pressure.
• Veins have large lumen and valves to try and keep the blood moving back to the heart because the pressure is low.
• Capillaries have permeable walls so substances can be transferred between the blood and tissues.

Question 7

How do the different parts of the heart work together to circulate blood?

Answer 7

• The left and right atria recieve blood from the veins.
• The left and right ventricles pump blood out into arteries.
• The semilunar, tricuspid and bicuspid valves prevent any backflow of blood.
• The pulmonary veins and the vena cava are the main veins carrying blood back to the heart.
• The aorta and pulmonary arteries carry blood away from the heart.

Question 8

Pulmonary artery

Answer 8

Takes deoxygenated blood to the lungs and is on the right side of the heart.

Question 9

Aorta

Answer 9

Takes oxygenated blood to the body and is on the left side of the heart.

Question 10

Vena cava

Answer 10

Brings deoxygenated blood from the body and is located on the right side of the heart.

Question 11

Pulmonary vein

Answer 11

Brings oxygenated blood from the lungs and is located on the left side of the heart.

Question 12

Tricuspid valve

Answer 12

Atrioventricular valve on the right side of the heart.

Question 13

Bicuspid valve

Answer 13

Atrioventricular valve on the left side of the heart.

Question 14

What are the semilunar valves?

Answer 14

The valves of the pulmonary artery and aorta.

Question 15

Why is the left ventricle stronger?

Answer 15

The left ventricle has a thicker muscle wall than the right ventricle because it has to pump blood all around the body rather than just to the lungs, which are close by.

Question 16

What is a double circulatory system?

Answer 16

The blood is pumped to the lungs and returns to the heart to be pumped to the body. This is called a double circulatory system. This means the blood is at a higher pressure and so flows to the tissues at a faster rate.