y3.2: human circulatory system ❣

Question 1

composition of blood

Answer 1

55% plasma, 45% blood cells and platelets

Question 2

functions of blood plasma

Answer 2

• plasma transports respiratory gases, nutrients, metabolic waste, hormones
• maintain homeostasis of the body (pH, water potential, temperature)

Question 3

red blood cells have a weird name.. what is it??

Answer 3

erythrocytes!

Question 4

structural adaptations of red blood cell to function

Answer 4

1) presence of haemoglobin: binds reversibly with oxygen
2) biconcave shape: increases surface area to volume ratio, increase rate of diffusion of gases
3) no nucleus: allows more haemoglobin to be packed in the cell
4) elastic: to squeeze through blood vessels smaller than itself without breaking

Question 5

what are white blood cells’ weird name and what are the types of white blood cells?

Answer 5

leucocytes: phagocytes and lymphocytes

Question 6

structure and function of phagocytes

Answer 6

• irregular in shape, with lobed nucleus so it can squeeze through capillary walls
• engulfs and ingests foreign particles such as bacteria by phagocytosis
• after phagocytosis, vesicles containing pathogens are formed
• vesicles fuse with lysosomes in phagocytes
• the hydrolytic enzymes in lysosomes digest the engulfed pathogen

Question 7

structure and function of lymphocytes

Answer 7

• round in shape, large nucleus
• lymphocytes produce antibodies, which causes identify and neutralise the pathogen

Question 8

what are platelets’ weird name?

Answer 8

thrombocytes!

Question 9

mechanism of blood clotting

Answer 9

• when blood tissues are damaged, damaged tissue and platelets produce thrombokinase
• thrombokinase converts prothrombin into thrombin
• thrombin converts soluble fibrinogen into insoluble fibrin threads that trap blood cells, forming a clot or scab
• fibrin clot tightens as platelets pull on fibrin threads, pulling edge of damaged vessels together to prevent further damage
• strengthen and stablise the fibrin clot, allowing repair of blood vessels to take place

Question 10

how does body prevent blood clots?

Answer 10

it has a anti-clotting substance called heparin
- thrombokinase neutralises heparin to allow clotting to take place

Question 11

why cant you donate to incompatible blood types?

Answer 11

antibodies in the recipients’ blood bind to antigens on the donor’s blood cells, causing the blood cells to agglutinate and rupture

Question 12

what are the advantages of double circulation?

Answer 12

1) complete separation of oxygenated and deoxygenated blood
- ensures only oxygenated blood can reach tissue cells, transported at a high efficiency
2) blood passes through the heart twice in a complete circuit
- blood enters the lungs at a lower pressure, hence flows more slowly through lungs and ensures sufficient time for the blood to be well-oxygenated
- oxygenated blood is distributed to the rest of the body tissues more quickly; maintains high metabolic rate

Question 13

structure and function of artery

Answer 13

structure
- thick, muscular, elastic walls
- no semi-lunar valves
- small lumen relative to diameter
function
- blood flows AWAY from the heart
- oxygenated except pulmonary and umbilical (2 umbilical arteries)

Question 14

structure and function of vein

Answer 14

structure
- thinner elastic and muscular wall
- semi-lunar valves present
- large lumen relative to diameter
function
- blood flows TO heart
- deoxygenated blood except pulmonary and umbilical

Question 15

structure and function of capillary

Answer 15

structure
- one-cell thick epithelium
- very small lumen
function
- allow for exchange of nutrients and waste between blood and tissue fluid

Question 16

artery structural adaptations to function

Answer 16

1) arterial wall can withstand high blood pressure generated by contraction of ventricles
2) elastic tissue in walls enables it to stretch and recoil under high blood pressure
3) muscular tissue in walls allows for constriction and dilation of artery

Question 17

structural adaptations of vein

Answer 17

1) large lumen offers low resistance to blood flow
2) semi-lunar valves prevent backflow of blood at low blood pressure to ensure blood flow in one direction

Question 18

structural adaptations of capillary

Answer 18

1) one-cell thick wall allows oxygen, nutrients, carbon dioxide and waste products to easily diffuse through
2) blood pressure falls to low pressure in capillaries to ensurre sufficient time for exchange of substances to take place

Question 19

why is there a blood pressure drop from arteries to capillary?

Answer 19

1) due to increase in total cross-sectional area due to extensive branching of capillary
2) blood is further from heart

Question 20

what are the four main blood vessels?

Answer 20

(left)
- pulmonary veins (from lungs)
- aorta
(right)
- vena cava
- pulmonary artery (to lungs)

Question 21

why is there a difference in thickness between walls of left and right ventricle

Answer 21

• blood has to be pumped across a longer distance to rest of body compared to lungs
• blood going to lungs should be at a lower pressure to allow blood to flow more slowly and ensure sufficient time for gaseous exchange to take place
• hence, walls of the left ventricle are thicker than right ventricle in order to generate more pressure to pump blood

Question 22

describe the flow of blood in the left side of the heart from the lungs to the rest of the body

Answer 22

• blood enters the left atrium via the pulmonary artery
• when the pressure in the left atrium is higher than the pressure in the left ventricle, the bicuspid valve opens and blood flows into the left ventricle
• left atrium contracts to force the remaining blood into the left ventricle
• left ventricle contracts and the pressure in the left ventricle increases, pushing against the bicuspid valve and forcing it shut
• when the pressure in the left ventricle is higher than the pressure in the aorta, the semi-lunar valve opens and blood flows to the rest of the body via the aorta

Question 23

[refer to cardiac cycle graph] what is the order of valves opening and closing?

Answer 23

A: bicuspid/tricuspid valve closes (ventricle > atrium)
B: semi-lunar valve opens (ventricle > aorta/pulmonary vein)
C: semi-lunar valves closes
D: bicuspid/tricuspid valve opens

Question 24

what are the causes, effects and treatment of atherosclerosis (coronary heart disease)?

Answer 24

• causes: high salt and sugar intake, lack of exercise, family history
• effects: patient may experience angina (heart pain) because heart tissues do not get sufficient oxygen and nutrients due to narrowing of coronary artery lumen; this results in tissue death and heart attack
• treatments: use a stent or coronary artery bypass grafting