circulatory system

Question 1

Why might the body of the recipient of a transplant reject the transplanted tissue / organ?

Answer 1

A recipient’s white blood cells may recognize the transplanted tissue / organ as a foreign substance and destroy the transplanted tissue / organ.

Question 2

What is the main cause of tissue rejection in patients who have just received an organ transplant?

Answer 2

release of antibodies

Question 3

Patients who suffer serious burns on their skin might require a skin transplant.
Doctors would transplant the patient’s own skin, obtained from other parts of the patient’s body to the burnt area.
Suggest why this is preferred, instead of using skin from another donor.

Answer 3

Since the patient’s own skin is not recognised as a foreign substance, using it will not lead to organ rejection.
However, the use of skin donated from someone else could lead to organ rejection. This is because the patient’s white blood cells will recognise the donor’s skin as a foreign substance and attack the donor’s tissues and organ.

Question 4

Suggest how training at high altitudes could improve an athlete’s performance at sea level. (3m)

Answer 4

1. increase in RBC so more haemoglobin present to carry more oxygen
2. With increased blood flow, more glucose and oxygen is transported to the exercising muscle cells.
3. Thus higher rate of respiration can take place to release more energy, improving the athlete’s performance.

Question 5

Suggest how blood clotting is affected when heparin is injected (heparin activates a protein called anti-thrombin. In turn, anti-thrombin inactivates thrombin by binding to it) (2m)

Answer 5

Inactive thrombin is unable to convert soluble fibrinogen to insoluble fibrin threads [1];
Fibrin mesh is not formed, and the blood does not clot [1]

Question 6

Describe how phagocytes destroy pathogens (4m)

Answer 6

they will engulf/endocytose/invaginate the parasite [1];
To form a phagosome/phagocytic vesicle [1];
Which will fuse with a lysosome containing hydrolytic enzymes [1];
The hydrolytic enzymes will digest the parasite [1]

Question 7

Explain why vaccinated individuals rarely fall sick with malaria upon subsequent exposure to the Plasmodium parasite. (4m)

Answer 7

Memory cells are formed after the vaccination [1];
Upon a second infection, secondary immune response is elicited [1];
Memory B cells quickly divide and differentiate into plasma cells [1];
Which produce much more antibodies to target the Plasmodium parasite [1

Question 8

Some people still fall ill with malaria despite being vaccinated. Suggest a reason for the limited effectiveness of the vaccine.

Answer 8

There is a large variety of malaria antigens. OR
The malaria antigens change structure very often. OR
The memory cells have died. OR
The person has a weakened immune system due to pre-existing illness (e.g. AIDS)

Question 9

What is the importance of activating B cells?

Answer 9

B cells are activated by helper T cells to produce plasma cells which later produce antibodies.

Question 10

is blood an organ, tissue or complex tissue and reason

Answer 10

COMPLEX tissue
made of diff grps of cells

Question 11

What is the main function of plasma

Answer 11

Transport materials (e.g. nutrients & hormones) and blood cells throughout the body

Question 12

Main function of wbc

Answer 12

remove pathogens that invade body and produce antibodies, helping body defend against diseases

Question 13

main function of rbc

Answer 13

transport oxygen to cells in body

Question 14

main function of platelets

Answer 14

involved in blood clotting

Question 15

explain how oxygen gets transported from the lungs to the cells

Answer 15

1. oxygen diffuses from alveoli –> blood
2. haemoglobin + oxygen –> oxyhaemoglobin
3. blood transports oxygen
4. oxyhaemoglobin releases oxygen

Question 16

where are rbc produced in fetus vs adults

Answer 16

fetus: liver (sometimes spleen & lymph nodes)
adults: bone marrow of certain bones

Question 17

how does the presence of haemoglobin help rbc with their function

Answer 17

• combines with O2 reversibly –> oxyhaemoglobin
• transport oxygen

Question 18

how does the circular, flattened biconcave shape of rbc help it in its function

Answer 18

increases surface area to volume ratio to increase rate of diffusion of oxygen and carbon dioxide into and out of cell

Question 19

state and explain the thickness of the muscular wall in the heart

Answer 19

• muscular wall of the left ventricle is thicker than the muscular wall of the right ventricle.
• left ventricle has to exert a greater pressure to pump blood to all parts of the body (further distance)
• right ventricle only has to pump blood to the lungs (shorter distance).

Question 20

Why is it important to have a median septum to completely separate the left and right side of the heart?

Answer 20

• right ventricle receives the deoxygenated blood from the body and pumps it to the lungs.
• left ventricle receives oxygenated blood from the lungs and pumps it to the body.
• median septum separates these two different chambers so that blood can be individually pumped out of the heart to the lungs and the rest of the body.

Question 21

There is a birth defect called “ventricular septal defect” where a baby is born with a hole in the median septum that separates the two ventricles of the heart.
Suggest how this defect might affect the health of the baby over time.

Answer 21

• blood flows from the left ventricle through the defect to the right ventricle and into the lungs.
• extra blood being pumped into the lungs forces the heart and lungs to work harder
• if not repaired, this defect can increase the risk for other complications, including heart failure, high blood pressure in the lungs, irregular heart rhythms, or stroke.

Question 22

What is the function of the atrioventricular valves (bicuspid and tricuspid valves)?

Answer 22

prevent the backflow of blood into the atria when the ventricles are contracting

Question 23

Explain the role of the chordae tendineae during ventricular systole

Answer 23

hold the bicuspid and tricuspid valves in place and to prevent the valves from flipping backward into the atria

Question 24

All arteries, except the
______ artery, carry oxygenated blood.

Answer 24

pulmonary

Question 25

The ________ artery and vein transports blood between the lungs and the heart.

Answer 25

pulmonary

Question 26

The _____ vein transports blood from the liver to the heart

Answer 26

hepatic

Question 27

The hepatic portal vein carries blood from the ______ to the ________

Answer 27

small intestine; liver

Question 28

The renal artery carries blood from the ______ to the ______

Answer 28

heart; kidneys

Question 29

why does the left ventricle has a thicker and more muscular wall than the right ventricle

Answer 29

- pumps blood over a longer distance to all parts of the body, compared to the right ventricle which pumps blood only to the lungs. - wall of the left ventricle is thicker so that when its muscles contract, it can generate a higher pressure needed to push the blood further.

Question 30

state the path of a rbc (start from vena cava and end at aorta)

Answer 30

vena cava -> right atrium -> right ventricle -> pulmonary artery -> lungs -> pulmonary vein -> left atrium -> left ventricle -> aorta

Question 31

describe the sequence of events for deoxygenated blood in the cardiac cycle (7)

Answer 31

1. deoxygenated blood from various parts of the body is returned to the right side of the heart 2. muscles of right and left atria contract 3. blood enters right ventricle 4. left and right ventricles contract 5. tricuspid valve closes 6. blood enters pulmonary arteries and is sent to the lungs 7. pulmonary valve closes

Question 32

describe the sequence of events for oxygenated blood in the cardiac cycle (7)

Answer 32

1. oxygenated blood from lungs is sent to the left side of the heart 2. muscles of right and left atria contract 3. blood enters left ventricle 4. left and right ventricles contract 5. bicuspid valve closes 6. blood enters aorta and is sent to the other body parts 7. aortic valve closes

Question 33

summarise the sequence of events and changes in pressure in the left side of the heart. (9)

Answer 33

1. Muscles of the left atrium contract. Pressure in the left atrium increases until it becomes higher than the pressure in the left ventricle. Bicuspid valve opens. Blood is forced into the left ventricle. 2. Muscles of the left atrium relax while muscles of the left ventricle start to contract 3. Pressure in the left ventricle increases until it becomes higher than the pressure in the left atrium. The bicuspid valve closes 4. Muscles of the left ventricle continue to contract. 5. Pressure in the left ventricle continues to increase until it becomes higher than the pressure in the aorta. The semi-lunar valve in the aorta opens. Blood enters the aorta. 6. Muscles of the left ventricle begin to relax. 7. Pressure in the aorta becomes higher than that of the left ventricle. The semi-lunar valve in the aorta closes 8. Muscles of the left ventricle continue to relax and its pressure decreases 9. Pressure in the left ventricle becomes lower than that in the left atrium. The bicuspid valve opens

Question 34

how does being elastic and can turn bell-shaped help rbc

Answer 34

squeeze through blood vessels smaller than itself in diameter w/o breaking move easily through narrow capillaries

Question 35

what doe plasma transport

Answer 35

- plasma proteins (blood clotting and maintain water potential of blood) - antibodies - respiratory gases - nutrients

Question 36

which blood vessel has the highest temp.

Answer 36

Hepatic vein as liver goes through a lot of reactions

Question 37

how does plasma maintain homeostatis

Answer 37

- optimum pH of blood - wp of blood (wp largely due to soluble sodium ions and plasma proteins; blood solute levels regulate movement of water between blood and tissues) - tmep (water distributes heat)

Question 38

features of phagocytes and functions

Answer 38

- lobed nucleus: move, change shape, squeeze through capillary walls - engulfs and digests pathogens by phagocytosis - granular cytoplasm

Question 39

explain phagocyte action

Answer 39

1. attracted to wounds/sites of infection --> squeeze out between the epthelial cells of capillaries (contain lysosomes) 2. recognises pathogens --> pseudopodia --> engulf --> vesicle 3. vesicle fuses with lysosome --> hydrolytic enzymes chemically digest pathogen

Question 40

features of lymphocytes

Answer 40

- large rounded nucleus - small amt of non-granular cytoplasm

Question 41

function of lymphocytes

Answer 41

produce antibodies protect body from pathogens by: - agglutination (bacteria clump --> attract phagocytes to engulf by phagocytosis) - neutralises toxins produced

Question 42

explain the mechanism of blood clotting

Answer 42

1. damaged tissue & platelet produce thrombokinase 2. thrombokinase convert prothrombin --> thrombin 3. thrombin convert soluble fibrinogen --> insoluble fibrin threads that trap bloos cells --> clot/scab

Question 43

function of platelets

Answer 43

prevent excessive blood loss and entry by pathogens

Question 44

function of artery

Answer 44

transport blood away from heart

Question 45

function of veins

Answer 45

transport blood towards heart

Question 46

function of blood capillary

Answer 46

for exchange of substances between blood and tissue fluid (to body cells)

Question 47

structure of artery

Answer 47

thick, muscular, elastic walls narrow lumen valves absent

Question 48

structure of blood capillary

Answer 48

Wall is one-cell thick Lumen narrow (abt size of one red blood cell) Valves are absent

Question 49

structure of veins

Answer 49

Thin muscular wall Wide lumen Valves present

Question 50

Blood pressure & speed of blood flow in artery

Answer 50

Higher pressure than veins & capillaries Blood flows rapidly

Question 51

Blood pressure & speed of blood flow in veins

Answer 51

Lower pressure than arteries & capillaries Blood flows slowly (faster than in capillary) -- skeletal muscle contractions assist (exerts pressure on forces blood upwards)

Question 52

Blood pressure & speed of blood flow in capillaries

Answer 52

Lower pressure than in artery. Blood pressure falls along the capillaries from the arteriole end to the venule end due to the increase in total cross-sectional area Blood flows slowest

Question 53

adaptation to function for arteries

Answer 53

- arterial wall can withstand high pressure - elastic tissue can stretch and recoil under high pressure --> push blood - muscular tissue allows for constriction and dilation to regualte blood volume

Question 54

adaptation to function for capillaries

Answer 54

- one-cell thick wall, easily diffuse - intercellular clefts --> increase rate of diffusion of materials - extensive network surrounding cells --> efficient exchange

Question 55

adaptation to function for veins

Answer 55

- large lumen --> smooth flow of blood - semi-lunar valves to prevent backflow of blood

Question 56

outline the cardiac cycle in terms of what happens during ventricular systole and diastole

Answer 56

1. Ventricular Systole (contract): i. Ventricle muscles contract. The rising pressure of blood in the ventricles pushes the AV valves upwards, forcing them shut to prevent backflow. This produces a 'lub' sound. ii. When the pressure in the ventricles become higher than that of the aortic/pulmonary artery pressure, the semi-lunar valves are pushed open Blood in the ventricles enter the aorta/pulmonary artery. 2. Ventricular Diastole (relax): i. The ventricle muscles then relax, causing pressure within the ventricle chambers to fall. Blood pumped out of the heart starts to flow backwards, which pushes the semi-lunar valves closed. This produces a 'dub' sound. When ventricular pressure drops below atrial pressure (which is rising due to the passive filling of the atria with new blood; the AV valves are pushed open and blood flows into ventricles passively.

Question 57

describe coronary heart disease in terms of occlusion of coronary arteries

Answer 57

Coronary arteries branch from aorta to provide oxygen and nutrients Atherosclerosis: build up of cholesterol & fatty deposists Plaquw narrows lumen --> less oxygen & nutrients supplied --> blocked --> tissue death --> heart attack Patients may experience anigna

Question 58

factors that increase risk of heart attack

Answer 58

lifestyle: - smoking - lack of exercise non-lifestyle: - age - family history

Question 59

outline the cardiac cycle in terms of what happens during atrial systole and diastole

Answer 59

1. Atrial Systole (contract): Atria muscles contract. Pressure in the atria rise, forcing blood through the open atrioventricular (AV) valves into the ventricles. 2. Atrial Diastole (relax): Atria muscles then relax (at the same time as ventricular systole) Blood from pulmonary veins and vena cava start filling the atria again.