Chapter 8: Transport in Humans

Question 1

Why is there a need for transport systems? (in multicellular organisms)

Answer 1

1. Many cells are too far from the external environment so they need to be carried via transport system to reach them
2. Large body with small surface area to volume ratio causes the exchange of substances between the body and the external environment to be very slow.

Question 2

Describe plasma and its functions

Answer 2

Plasma is a transport medium, and a pale yellowish liquid.
Plasma is 90% water, and a complex mixture of various dissolved substances:
1. Soluble proteins Fibrinogen, antibodies, and prothrombin
2. Dissolved minerals (chlorides and sulphates of calcium and sodium)
3. Food substances (glucose, amino acids, fats and vitamins)
4. Excretory products (urea, uric acid and creatinine)
5. Hormones

Question 3

Describe the red blood cells and how its adaption allows it to perform its function.

Answer 3

RBC’s are produced in the bone marrow. They have:

1. No nucleus, which allows for more space for haemoglobin, to transport ombre oxygen in the red blood cells to other body cells
2. Biconcave in shape, which increases surface area to volume ratio for a faster rate of exchange of oxygen gas
3. Elastic and can turn bell-shaped, to squeeze through within blood vessels that are smaller in diameter than the red blood cells

Question 4

What happens to red blood cells when they are worn out?

Answer 4

When worn out, red blood cells are broken in the spleen. The haemoglobin is released, and transported to the liver to be broken down. Iron that is released from haemoglobin is stored in the liver, and bile pigment is also released from haemoglobin that emulsifies fats to increase surface area to volume ratio of fats for a faster rate of digestion of fats catalysed by lipase

Question 5

Explain how people adapt to living at a high altitude (hint: RBC - Oxygen)

Answer 5

There is a lower concentration of oxygen at a higher altitude. Therefore the people would have a higher proportion of red blood cells in their blood, increasing haemoglobin content per unit volume of blood so that more oxygen can be transported to the tissuew2 cells per unit time.

Question 6

State 3 characteristics of WBC

Answer 6

1. Colourless as they do not contain haemoglobin
2. Are irregular in shape and contain a nucleus
3. can move, change shape, and squeeze through the walls of the thinnest blood capillaries into the spaces among tissue cells.

Question 7

Explain the functions of antibodies and where they are made from

Answer 7

Lymphocytes produce antibodies that;

1. Neutralise toxins produced by bacteria
2. Destroy bacteria by attaching itself to them and causing their cell surface membrane to rupture
3. Cause bacteria to agglutinate so that they can be easily ingested by phagocytes.

Question 7

Explain the functions Phagocytes

Answer 7

Phagocytes carry out phagocytosis which is the process of engulfing or ingesting foreign particles and digesting them.

Question 8

How are antibodies formed by immunisation/vaccination?

Answer 8

Injection of dead or weakened forms of the pathogen is given to the person, to stimulate persons immune system to produce antibodies against the pathogen.

Question 8

State 2 ways to prevent tissue/organ rejection and possible problems in methods

Answer 8

1. Ensure the tissues of donor and recipient are as genetically close as possible
2. Use of immunosuppressive drugs which inhibit the responses of recipient’s immune system.

Possible problems in using immunosuppressive drugs:

1. Recipient’s would have a lower resistance to many kinds of infections since immune system is being suppressed
2. Recipients may have to continue taking the drugs for the res of his or her life, to continually suppress the possible tissue rejection.

Question 9

List the characteristics of Arteries

Answer 9

1. Transport blood away from the heart to rest of body (with exception to the pulmonary artery, which is from heart to lungs)
2. Transports oxygenated blood to the rest of the body, except the pulmonary artery which transports deoxygenated blood to the lungs
3. The pressure of blood is high - Small lumen(empty, hollow. continuous space)
4. Fast speed(due to the high pressure)
5. blood moves in pulses, reflecting the rhythmic pumping action of the heart
6. Has a thick, muscular and elastic wall to withstand the high pressure of blood coming from the heart.
7. Small and narrow lumen
8. No valves are present

Question 10

List the characteristics of veins

Answer 10

1. Usually carries deoxygenated blood into the heart from the rest of the body (with exception to the pulmonary vein which carries oxygenated blood from the lungs to the heart)
2. Low pressure of blood
3. Blood flows at slow speeds
4. No blood pulse
5. Has thin, less muscular and less elastic wall
6. Large and wide lumen
7. Valves are present to prevent the back flow of blood so that blood will flow in one direction only

Question 11

List the characteristics of capillaries

Answer 11

1. Link arteries and veins
2. Blood changes from oxygenated blood at the arteriole end to deoxygenated blood at the venue end
3. Low pressure of blood (Blood pressure decreases from arteriole end to venue end)
4. Blood travels at low speeds to allow fro more time for exchange of substances
5. No pulse
6. No muscle wall, endothelium is once-cell thick only and is partially permeable
7. Large lumen
8. No valves present

Question 12

How are substances transferred between capillaries and tissue cells?

Answer 12

Dissolved food substances and oxygen diffuse from the blood in blood capillaries into the tissue fluid and then into the cells. Metabolic waste products such as urea and carbon dioxide diffuse from the cells into the tissue fluid then through the blood capillary walls into the blood.
The blood transports these to excretory organs for removal

Question 13

What are the advantages of a double circulation?

Answer 13

1. Blood entering the lungs is at a lower pressure compared to blood leaving the heart. This ensures that the blood flows more slowly throughout the lungs, allowing sufficient time for the blood to be well oxygenated before it is return to the heart.
2. The heart pumps oxygenated blood at high pressure to the rest of the body, so oxygenated blood is distributed to the Boyd tissues more quickly. This helps to maintain the high metabolic rate in mammals.

Question 14

State a few features of the heart

Answer 14

1. Size of a clenched fist
2. Lies in the thorax behind the chest bone and between the 2 lungs
3. It has a roughly conical shape
4. Surrounded by the pericardium, with a fluid between the two pericardial membranes to help reduce friction when the heart is beating

Question 15

What is the function and the consequence of a faulty median septum?

Answer 15

The median septum prevents the mixing of deoxygenated blood in the right side with the oxygenated blood in the left side. Mixing of deoxygenated with oxygenated blood will reduce the amount of oxygen carried to the tissue cells.

Question 16

Why does the left side of the heart have thicker muscular walls than the right side of the heart? (ventricles)

Answer 16

1. The left ventricle has thicker muscular walls as it has to pump blood round the whole body and this requires a high pressure. The right ventricle has thinner walls than the left ventricle since it only pumps blood to the lungs, which is close to the heart.

Question 17

Describe the flow of blood in the heart (6 steps)

Answer 17

1. Deoxygenated blood returns from the rest of the body to the right atrium of the heart through the vena cava.
2. When the right atrium has higher blood pressure than the right ventricle, the tricuspid valves will open to allow blood to flow into the relaxed right ventricle from the contracted right atrium. This causes the lub sound.
3. Blood flows from the contracted ventricle into the lungs, through the pulmonary arteries. For this to happen, the semi-lunar valves in the pulmonary arch open.
4. As the right ventricle relaxes, semi-lunar valves in the aortic arch will close, to prevent the back flow of blood into the right ventricle from the lungs. This causes the dub sound.
5. Blood in the pulmonary arteries are transported to the lungs for oxygenation of blood
6. Oxygenated blood returns from the pulmonary vein into the left atrium.
7. When the left atrium has higher blood pressure than the left ventricle, the bicuspid valves open to allow blood from the contracted left atrium to flow into the relaxed left ventricle.
8. When the left ventricle has higher blood pressure than the left atrium, bicuspid valves close to prevent back flow of blood from contracted left ventricle to the relaxed left atrium. This causes the lub sound.
9. Blood flows from the contracted left ventricle to other parts of the body through the aorta. For this to happen, the semi-lunar valves in the aorta must open.
10. As the left ventricle relaxes, the semi-lunar valves in the aortic arch will close, to prevent the back flow of blood into the left ventricle from the aorta. This causes the dub sound.

Question 18

Describe the cardiac cycle (7 steps). After doing so, define the two terms ventricular systole and ventricular diastole.

Answer 18

1. Both atria contract, forcing blood into the two relaxed ventricles.
2. The higher pressure in both atria than in both ventricles, causes the atrio-ventricular valves to open to allow flow of blood from contracted atria into relaxed ventricles.
3. After a short while, both ventricles contract
4. The increased pressure in both ventricles, cause the atria-ventricular valves to close, to prevent back flow of blood from both ventricles into both atria. This causes a sub sound
5. The blood from the right ventricle flows into the pulmonary arteries to lungs while the blood from left ventricle flows into the aortic arch to rest of the body. Opening of semi-lunar valves allows the blood flow.
6. As both ventricles contract, both atria relax. The right atrium receives blood from the vena cava while the left atrium receives blood from the pulmonary veins.
7. Both ventricles relax. this causes a decrease in pressure in both ventricles, causing the semi-lunar valves in pulmonary arch and aortic arch to close. this causes a dub sound.

Ventricular systole = contraction of the ventricles
Ventricular diastole = relaxation of the ventricles