Section 2: h) (Human) Transport

Question 1

Describe the composition of the blood.

Answer 1

Made up of liquids and solids:

Solid part (45%):

• Red blood cells (contain haemoglobin, which contains iron)
• White blood cells
• Platelets

Liquid part (55%):
-Plasma (made up of water, salts and protein)

Question 2

What does plasma transport?

Answer 2

• Red blood cells
• White blood cells
• Platelets
• Digested food (e.g. glucose & amino acids) - from gut to all body cells
• Carbon dioxide - from body cells to lungs
• Urea - from liver to kidneys
• Hormones
• Heat energy

Question 3

What are the adaptations of red blood cells which make them suitable for carrying oxygen?

Answer 3

• Biconcave shape (shaped like a flat disc)= large surface area for absorbing and releasing oxygen.
• Absence of nucleus = creates room inside cell for more haemoglobin, so they can carry more oxygen.
• Contain haemoglobin (a red chemical which contains iron) = in the lungs: reacts with oxygen to form oxyhaemoglobin, in body tissues: oxyhaemoglobin breaks down to haemoglobin, releasing oxygen from the red blood cell to the cells.
• Small and flexible = allows them to pass through capillaries (only one cell thick).

Question 4

What are the structural adaptations of white blood cells which make them suitable for ingesting pathogens?

Answer 4

They have a lobed nucleus and an irregular shape, which enables them to change shape when they are ingesting pathogens by surrounding and engulfing them until they are completely enclosed.

Question 5

What are phagocytes and what is their function?

Answer 5

Phagocytes are a type of white blood cells that kill pathogens by surrounding and engulfing them until they are completely enclosed and then digesting them by enzymes. Different types of phagocytes target different types of pathogens (e.g. bacteria, fungi and protoctist parasites).

Question 6

What are antigens?

Answer 6

Antigens are proteins found on the surface of a substance (often a pathogen) that trigger an immune response. Different antibodies attach to different pathogens, so the body’s immune system can recognise foreign antigens (antigens that are not normally produced by the body, but by pathogens instead).

Question 7

What are lymphocytes and what is their function?

Answer 7

Lymphocytes are a type of a white blood cell which produce chemicals called antibodies. These are molecules which are shaped to fit onto invaders’ antigens. When a pathogen infects the body, lymphocytes produce antibodies specific to that pathogen. Antibodies stick onto foreign microorganisms in the blood, which either kills the microorganisms or causes them to clump together, making it easier for phagocytes to engulf and destroy them.

Question 8

What are memory cells?

Answer 8

Lymphocytes produce memory cells. These remain in the blood after a pathogen has been destroyed, sometimes for the rest of a person’s life. Memory cells produce a quick response if the antigen is encountered again.

Question 9

How do vaccinations work?

Answer 9

• Vaccination is a way of preventing disease by making the body respond as if it has already been infected.
• Vaccine prepared from small amounts of material from the pathogen, which is either dead or weakened so that it cannot cause infection.
• Vaccine put into body, through mouth (polio) or by injection.
• Lymphocytes make antibodies specific to pathogen and memory cells (remain in blood after pathogen = destroyed).
• If you are infected by live pathogen in future, memory cells recognise it very rapidly and stimulate lymphocytes to produce antibodies sooner, faster + in greater quantity.
• This kills off pathogen, often before you develop symptoms + realise you have been infected.
• Rapid response makes you immune to pathogen.

Question 10

What are platelets and what is their function?

Answer 10

Platelets are small fragments of cells; they have no nucleus and are suspended in the blood plasma.

When the wall of a blood vessel is damaged, platelets clump together to ‘plug’ the damaged area. This is known as blood clotting, which prevents blood loss and the entry of microorganisms into the blood from the wound.

Question 11

Describe the structure of the heart.

Answer 11

• Inside the heart there are four chambers - two on the left and two on the right.
• The chambers on the left hand side are separated from the chambers on the right hand side by a thick section of cardiac muscle called the septum.
• The top two chambers are called the left atrium and the right atrium.
• The bottom two chambers are called the left ventricle and the right ventricle.

Question 12

How does the heart function?

Answer 12

1) The right atrium of the heart receives deoxygenated blood from the body (through the vena cava).
2) The deoxygenated blood moves through to the right ventricle, which pumps it to the lungs (via the pulmonary artery).
3) The left atrium receives oxygenated blood from the lungs (through the pulmonary veins).
4) The oxygenated blood then moves through to the left ventricle, which pumps it out round the whole body (via the aorta).

Question 13

Why does the left ventricle have much thicker and more muscular walls than the right ventricle?

Answer 13

The left ventricle has to pump blood around the whole body, whereas the right ventricle only has to pump it to the lungs. This also means that the blood in the left ventricle is under higher pressure than the blood in the right ventricle.

Question 14

How does the heart rate change during exercise?

Answer 14

Heart rate increases during exercise in order to pump blood more rapidly around the body. This supplies oxygen and glucose more quickly to respiring cells particularly in the muscles, and removes waste products faster.

Question 15

How does the heart rate change under the influence of adrenaline?

Answer 15

1) When an organism is threatened (e.g. by a predator) the adrenal glands release adrenaline.
2) Adrenaline binds to specific receptors in the heart. This causes the cardiac muscle to contract more frequently and with more force, so heart rate increases and the heart pumps more blood.
3) This increases oxygen supply to the tissues, getting the body ready for action.

Question 16

What is coronary heart disease?

Answer 16

• Affects the two coronary arteries branching from the aorta to supply all the muscles of the heart in both the atria and the ventricles.
• Caused by accumulation of atheroma (fatty material consisting of cholesterol [a lipid], dead muscle cells and platelets).
• Build up of atheroma forms deposits called plaques in lining of arteries, which cause artery walls to become less elastic.
• Arteries become narrower + restrict blood flow.
• Blood can no longer flow smoothly and is more likely to clot, forming a thrombus.
• Blood clots can interrupt blood flow even more/completely block artery.
• Heart attack occurs when large branch of coronary artery = obstructed by a blood clot, so muscle around it is starved of oxygen + glucose, meaning it can’t respire, so it dies.

Question 17

Give some factors that can increase the risk of coronary heart disease.

Answer 17

• Sex: Men are more at risk than women; oestrogen provides some protection in women.
• Age: Risk increases with increasing age; about 80% of people who die of coronary heart disease are 65 or over.
• Body mass: Being overweight or obese increases risk; excess weight puts more strain on the heart.
• High blood pressure: Risk increases with increasing blood pressure.
• Diet: Risk increases with a high intake of saturated fat & salt (found in red meat + processed foods); risk decreases with high intake of fruit, vegetables and fibres, & a moderate intake of unsaturated fats (found in fish).
• Exercise: Lack of exercise increases risk; as more aerobic exercise is taken, risk decreases.

Question 18

What can be done to reduce the chances of getting coronary heart disease?

Answer 18

• Giving up smoking (and drinking)
• Eating less saturated fat
• Losing weight
• Taking regular aerobic exercise (aim for at least 150 minutes of moderate activity e.g. cycling/fast walking every week).

Question 19

Name the three types of blood vessel.

Answer 19

Arteries, veins, capillaries

Question 20

Which vein is the exception to the rule that veins carry deoxygenated blood?

Answer 20

Pulmonary vein

Question 21

Which artery is the exception to the rule that arteries carry oxygenated blood?

Answer 21

Pulmonary artery

Question 22

Why do veins contain valves?

Answer 22

Valves prevent the backflow of blood to ensure that it only flows in one direction.

Question 23

Why do arteries not need valves?

Answer 23

The pressure from the heart is so strong that blood is only able to flow in one direction.

Question 24

What substances go into the bloodstream and come out of the bloodstream at the capillaries in the lungs?

Answer 24

Oxygen goes into the bloodstream and carbon dioxide comes out of the bloodstream at the capillaries in the lungs.

Question 25

What substances go into the bloodstream and come out of the bloodstream at the capillaries around body cells?

Answer 25

Carbon dioxide goes into the bloodstream (out of cells) and oxygen comes out of the bloodstream (into cells) at the capillaries around body cells.

Question 26

How does the structure of arteries relate to their function?

Answer 26

• Thick, muscular walls - protect arteries from bursting due to high pressure
• Narrower lumen than in veins
• Elastic fibre - allows them to expand
• Recoil of elastic wall after pulse of blood has passed through artery - helps maintain blood pressure and even out pulses

Question 27

How does the structure of veins relate to their function?

Answer 27

• Walls not as thick as artery walls - blood is under very low pressure
• Wider lumen than arteries - helps the blood flow despite low pressure
• Valves - prevent backflow of blood and make sure it can only flow in right direction.

Question 28

Where are capillaries found?

Answer 28

In organs and tissues.

Question 30

What organs does the circulatory system consist of and what do they do?

Answer 30

It consists of the heart and blood vessels (arteries, veins, capillaries). The blood vessels carry blood to the organs, tissues and cells, and the heart is the pump that forces the blood around the body and back again to the heart.

Question 31

What artery and what vein supplies the lungs?

Answer 31

Pulmonary artery, Pulmonary vein

Question 32

What artery and what vein supplies the heart?

Answer 32

Vena Cava, Aorta

Question 33

What artery and what vein supplies the liver?

Answer 33

Hepatic artery, Hepatic vein

Question 34

What artery and what vein supplies the kidneys?

Answer 34

Renal artery, Renal vein

Question 35

How does the structure of capillaries relate to their function?

Answer 35

• Very small - can carry blood close to any cell and exchange substances with them.
• Thin walls (only one cell thick) - increases rate of diffusion by providing a short diffusion pathway for substances to pass through.
• Permeable walls - so substances can diffuse in and out.
• Water and other substances squeezed out into surrounding intercellular spaces - blood is under pressure.

Question 36

The heart muscles have their own blood supply. What are these arteries called and from which blood vessel do they branch?

Answer 36

Coronary arteries, they branch from the aorta.

Question 37

Why does the heart need its own blood supply?

Answer 37

As it needs oxygen and other nutrients to stay healthy. Therefore, it pumps oxygen-rich blood to its own muscle through the coronary artery.