Circulation

Question 1

What is the main artery called?

Answer 1

Aorta

Question 2

What is the blood vessel going to the lungs called?

Answer 2

Pulmonary artery

Question 3

What is the only artery carrying deoxygenated blood?

Answer 3

Pulmonary artery

Question 4

What are the components of the blood?

Answer 4

Plasma, red blood cells, white blood cells, platelets.

Question 5

What is the ratio of plasma to blood cells?

Answer 5

55% plasma
45% blood cells

Question 6

Describe red blood cells.

Answer 6

Red blood cells carry oxygen around the human body. They are a biconcave disc, which increases the surface area, which increases the rate of diffusion. They are red because of haemoglobin, which is a red pigment that reversibly binds to oxygen. Where there is a lot of oxygen (the lungs), the haemoglobin binds to the oxygen. Where there is not a lot of oxygen (muscles), the haemoglobin drops the oxygen off.

Question 7

Describe red blood cell’s adaptations.

Answer 7

These are red blood cells and carry oxygen around the human body. They are a biconcave disc, which increases the surface area, which increases the rate of diffusion. They are red because of haemoglobin, which is a red pigment that reversibly binds to oxygen. The thinness of the cell gives short diffusion centre and there are very thin cell surface membranes which allow oxygen to diffuse quickly.

Question 8

Describe haemoglobin.

Answer 8

Haemoglobin is a red pigment that reversibly binds to oxygen. Haemoglobin combines with oxygen and it forms oxyhaemoglobin, when oxygen is high in the surroundings. When the concentration of oxygen is low in the surroundings, oxyhaemoglobin turns back into haemoglobin as the red blood cell deposits the oxygen.

Question 9

Describe white blood cells

Answer 9

The main role is to protect the body against invasion of pathogens

Question 10

Describe platelets

Answer 10

They are fragments of cells. They form clots when the vessel wall is damaged.

Question 11

Describe Plasma.

Answer 11

Liquid part of the blood: mainly water. Carries the following around the body:
- Dissolved nutrients (glucose, amino acids, minerals, ions)
- Hormones
- Carbon dioxide
- Urea
Distributes heat around the body.

Question 12

What is meant by double circulation?

Answer 12

Humans have double circulation. We divide the circulatory system into:
- Pulmonary circulation: deoxygenated blood is pumper into the lungs and oxygenated blood returns to the heart.
- Systemic circulation: oxygenated blood is pumped to all other organs of the body and deoxygenated blood returns back to the heart.

Question 13

How does blood move around the heart?

Answer 13

• Blood enters the atria. However, initially, it cannot pass into the ventricles because the bicuspid and tricuspid valves are closed.
• The walls of the atria contract. This raises the pressure of the blood in the atria which forces open the bicuspid and tricuspid valves. Blood passes through these valves into the ventricles.
• When the ventricles are full, they contract. This increases the pressure of blood in the ventricles which closes the tricuspid and bicuspid valves. This stops blood returning to the atria.
• The ventricles continue to contract and the pressure continues to increase. This forces open the semi - lunar valves at the base of the aorta and the pulmonary artery. Blood is ejected into these two arteries. The pulmonary artery carries deoxygenated blood to the lungs. The aorta has branches that carry blood to all other parts of the body.
• As ventricles empty, higher pressure in the aorta and pulmonary arteries closes the semi-lunar valves. The cycle then begins as the atria start to fill blood.