6 — transport in humans

Question 1

Blood transports

Answer 1

• Digested food substances
• Excretory products (e.g. urea and carbon dioxide)
• Hormones
• Heat
• Oxygen

Question 2

Measures to prevent Tissue Rejection

Answer 2

• the immune system may recognise a donated organ or blood as foreign tissue and cause tissue rejection.
• Tissue matching avoids tissue rejection -> Donor and recipient should be genetically close
• The use of immunosuppressive drugs that inhibit the immune system to reduce risk of tissue rejection (side effect: lowered resistance to infections

Question 3

Blood clotting (coagulation)

Answer 3

Platelets involved in converting soluble protein, Fibrinogen (plasma protein) -(enzymes)-> insoluble fibrin threads -> entangles blood cells n forms a clot -> seals wound n prevents excessive loss of blood + entry of bacteria

Question 4

Plasma appearance + function

Answer 4

• Contains mainly water (90% of plasma volume)
• Yellowish liquid in blood
• consists of 55% of blood

Function
Transports dissolved substances in blood such as
- excretory products to excretory organs for removal (e.g. urea, creatinine, uric acid)
- Nutrients from SI such as glucose, amino acids, fats
- Blood cells around the body
- Hormones from endocrine glands to target organs

Question 5

Red blood cells adaptations + functions

Answer 5

Adaptations
- Contains haemoglobin that can combine reversibly with oxygen to form oxyhaemoglobin to release O2 to tissue cells
- Has circular biconcave shape to ^SA:V -> ^diffusion of O2 rate into + out of cell
- Absence of nucleus to max space available for haemogoblin
- Flexible and can change into a bell-shaped structure so that they can flow easily through narrow capillaries. Slows down due to tumbling action hence more time for absorption or release of oxygen.

Function
Transport oxygen from the lungs to other parts of the body

Question 6

White blood cells structure + function

Answer 6

Phagocytes:
- carry out phagocytosis to engulf and ingest foreign particles such as bacteria
Phagocytosis is the process by which a white blood cell engulfs and ingests foreign particles such as bacteria.

Lymphocytes:
produce antibodies that:
- cause pathogens to agglutinate (clump together) for easy engulfing and ingestion by phagocytes
- neutralise toxins produced by bacteria (antitoxin function)

Question 7

Platelets structure + function

Answer 7

Structure:
Fragments of cytoplasm. They contain an enzyme that catalyses the conversion of fibrinogen to fibrin threads.

Function:
Promotes blood clotting (coagulation) to prevent excessive blood loss n entry of harmful organisms into bloodstream

Question 8

Explain how the blood clots at a wound. [4]

Answer 8

• Damaged tissues and platelets release an enzyme known as thrombokinase. [1]
• Thrombokinase converts prothrombin in blood plasma to thrombin in the presence of calcium ions. [1]
• Thrombin converts soluble fibrinogen to insoluble fibrin threads. [1]
• which form a mesh to entangle blood cells and form a clot to seal the wound, thus preventing pathogens entering the wound causing infections / disease. [1]

Question 9

Explain why heart rate increases during exercise. [3]

Answer 9

1. Vigorous contraction of muscles require increasing energy demand. [1]
2. More blood transported to muscles to supply more oxygen and glucose [1]
3. for aerobic respiration to release more energy to meet energy demand [1]

Question 10

Antigens definition

Answer 10

Identifiable surface features of pathogens that WBCs learn to recognise

Question 11

Why is blood type O the universal donor

Answer 11

Blood type O is the universal donor: no antigens on the donor’s red blood cells -> antibodies in recipient’s blood plasma will not react with the red blood cells.

Question 12

Why is blood type AB the universal acceptor

Answer 12

Blood type AB is the universal acceptor -> no blood type antibodies in the blood plasma -> no agglutination of red blood cells in donor’s blood will occur.

Question 13

Explain why it is impossible for a person of blood type A to receive B type blood during blood transfusion. [3]

Answer 13

• Blood type A has A antigen on the surface of the RBC, thus the blood plasma contain B antibodies [1].
• Blood type B has B antigen on the surface of the RBC, upon transfusion, the B antibodies in plasma will bind with the transfused B antigen RBCs and cause agglutination. [1].
• Agglutination of RBCs will cause blockage in blood vessels resulting in heart attack / stroke / organ failure. [1]

Question 14

Adaptations of arteries

Answer 14

Walls r thick muscular and elastic to withstand the high blood pressure flowing within.

The elasticity helps the artery wall to stretch and recoil to push blood forward, giving rise to pulse

The contraction and relaxation of muscles in the arterial walls -> constriction n dilation of artery. Artery constricts, lumen narrows, less blood flows thru per unit time. Artery dilates, lumen widens, more blood flows /unit time.

Question 15

Function of arterioles and blood capillaries and veins

Answer 15

A: Transports oxygenated blood (except pulmonary arteries) from the heart to other parts of the body

BC: To facilitate exchange of substances between blood and tissue cells in the body.

V: Transport deoxygenated blood (except pulmonary veins) back to the heart.

Question 16

Adaptations of blood capillaries

Answer 16

Walls partially permeable, one-cell thick endothelium, made up of single layer of flattened cells – minimize diffusion distance for faster rate of diffusion.

Numerous branches of capillaries
- ^surface area for exchange of substances betw blood n tissue cells
- ^total cross-sectional area of the blood vessels, lowering the blood pressure and thereby slowing blood flow to give more time for exchange of substances

Continuous blood flow thru capillaries: maintain steep conc gradient for ^rate of exchange of substances

Question 17

Adaptations of veins

Answer 17

Blood in vein has lower pressure and speed, thus blood tends to backflow -> have valves to prevent backflow of blood.

In the veins, blood lower in pressure n spd compared to in the arteries -> walls of veins are relatively thinner compared to the walls of the arteries.

Question 18

Tissue fluid

Answer 18

Colourless liquid present in tiny spaces betw tissue cells that transports dissolved substances betw tissue cells n the blood capillaries.

Question 19

Transfer of substances betw capillaries n tissue fluids

Answer 19

• Dissolved food substances n O2 diffuse from blood -> blood capillaries -> tissue fluid -> tissue cells .
• Metabolic waste products diffuse from cells into tissue fluid -> blood capillary walls -> blood -> excretory organs for removal.

Question 20

Advantages of double circulation

Answer 20

During pulmonary circulation, (from heart to lungs to heart) the right ventricle has thinner walls that pumps deoxygenated blood to the lungs at lower pressure, allowing blood to flow thru lungs at lower spd, allowing sufficient time for blood to be fully oxygenated and CO2 to diffuse out before returning to the heart.

In systemic circulation (from heart to rest of the body back to heart), blood is pumped by the left ventricle which has thick walls, at high pressure, ensuring oxygenated blood and nutrients is quickly distributed to all the tissues in the body

Question 21

Compare and contrast between the structures of artery and vein. [4] (2S2D)

Answer 21

Similarities:
- Muscular and elastic tissue present [1]
- One cell thick endothelium present [1]

Differences:
- Vein has wider lumen than artery [1]
- Vein has semi-lunar valves along the vessel while artery don’t have [1]
- /Vein has thinner muscular and elastic layer compared to artery [1]

Question 22

Describe how a molecule of oxygen is transported from the alveoli to the heart muscles. [6]

Answer 22

1. Molecule of oxygen dissolves in the layer of moisture on the surface of the alveolus and diffuse from alveoli into blood down the concentration gradient. [1]
2. Binds with haemoglobin to form oxyhaemoglobin and transported in the blood capillaries. [1]
3. Oxygenated blood from the lungs enters the left atrium and left ventricle through the pulmonary veins via passive filling. [1]
4. Atrial systole, muscles in left atrium contracts forcing more oxygenated blood into left ventricle. [1]
5. Ventricular systole, muscles in left ventricle contracts and pressure in the ventricle becomes higher than in the aorta, forcing open the semi-lunar valve and forces oxygenated blood into the aorta. [1]
6. The oxygenated blood flows into coronary artery to supply the heart muscles with oxygen. [1]

Question 23

Explain how the presence of valves would help in maintaining one directional flow of blood in the heart. [6]

Answer 23

1. The flow is always from the atrium to the ventricle and then out of the heart via the aorta / pulmonary artery. [1]
2. During passive filling, both atrium and ventricle undergo diastole, bicuspid and tricuspid valve are open to allow blood to flow from atria into ventricles. [1]
3. During atrial systole, muscles in atria contracts and pressure increases, bicuspid and tricuspid valve are still open to allow more blood to flow from atria into ventricles. [1]
4. During ventricular systole, the bicuspid and tricuspid valve close to prevent the backflow of blood into the atria when the pressure in the ventricle is higher than that of the atria [1]
5. When the pressure of the ventricle is higher than that of the aorta / pulmonary artery, semi-lunar valve is forced open and blood is forced from ventricles into the aorta / pulmonary artery [1]
6. During ventricular diastole, the semi-lunar valve close to prevent backflow of blood back into ventricle as the pressure in ventricle drops below the pressure of aorta / pulmonary artery [1]
7. When pressure in ventricle drop below the pressure of atria, bicuspid / tricuspid valve open again to allow passive filling taking place for the next cycle. [1]

Question 24

What happens if u hv a hole in median septum

Answer 24

• Hole present in median septum -> blood flow thru hole mostly from LS to RS of heart since pressure in LS > RS -> mixing of oxygenated n deoxygenated blood -> less O2 for transportation to body cells for respiration.
• Patients may suffer from shortness of breath+ fatigue +/ heart failure

Question 25

Atria in heart vs ventricles

Answer 25

Atria:
- Collective term referring to 2 upper chambers LA&RA.
- Hv comparatively thin muscular walls since high pressure is not required, they only force blood into ventricles that lie directly below them.

Ventricles:
Hv comparatively thick muscular walls. Left ventricle muscle is much thicker to withstand the high pressure used to pump blood around the whole body.

Question 26

Median septum

Answer 26

Muscular wall that separates right n left sides of heart.

Median septum prevents mixing of deoxygenated blood in right side with oxygenated blood in left side to avoid reducing amt of O2 available to be carried to the rest of the body.

Question 27

Tricuspid valve vs bicuspid valve

Answer 27

TV:
- Prevents backflow of blood from RV to RA
- consists of 3 flaps that point downwards into the ventricle n attached to the walls of RV by chordae tendinae (chord-like tendons)

BV:
- Prevents backflow of blood from LV to LA
- Bicuspid valve has 2 flaps that point downwards into LV. Chordae tendinae prevent the flaps from being reverted into the atrium when the LV muscles contract.

Question 28

Aortic valve vs pulmonary valve

Answer 28

Aortic valve: (semi-lunar valve in aorta) (LS)
- Prevents backflow of blood from aorta to LV

Pulmonary valve (semi-lunar valve in the pulmonary artery) (RS)
- Prevents backflow of blood from pulmonary artery to RV

Question 29

Food of blood to heart

Answer 29

DO blood: Body -> venae Cavae -> RA -> thru TV into RV ->semi-lunar valves -> pulmonary artery

O blood: lungs -> PV -> LA -> thru BV into LV -> thru semi-lunar valves -> aorta (2 small coronary arteries emerge from aprta to bring O2 n nutrients to heart muscles.

Question 30

Cardiac cycle definition

Answer 30

Refers to the sequence of events that takes place in 1 heartbeat.

Question 31

Blood pressure definition

Answer 31

the force that blood exerts on the walls of blood vessels.
- Measured in mm of mercury.
- Highest during ventricular systole

Question 32

Pulse definition

Answer 32

produced aft every ventricular contraction as the heart pumps the blood.

Question 33

Cardiac cycle graph

Answer 33

1. Atrial systole + AVV opened: Atrial muscles contract, pressure^ in atria, forcing blood into ventricles.
2. Ventricular systole, AVV & SLV closed + lub sound: Ventricular muscles contract, pressure in ventricles rise above pressure in atria -> bicuspid n tricuspid valve closes to prevent backflow of blood into atria -> ‘Lub’ sound produced.
3. All valves still closed. No change in blood volume, blood continues to rise.
4. SLV open, blood leaves + passive filling: Pressure in ventricle rises higher than in aorta & PA. Semi-lunar valves open. Blood flows from RV n LV to pulmonary artery n aorta respectively. Passive filling occurs, RA n LA receives blood from VC n pulmonary veins respectively.
5. Ventricular diastole + SLV closed + dub sound: Ventricular diastole occurs, pressure in ventricles falls below that of arteries -> semi-lunar valves close to prevent backflow of blood from PA & A into ventricles -> ‘dub’ sound produced
6. All valves closed. No change in vol of blood
7. AVV open: Bicuspid n tricuspid valve opens when pressure in ventricle is lower than that in atrium.
8. Pressure in ventricle rises as blood continues to enter ventricle from atrium. Whole cycle repeats

Question 34

Cause of Coronary heart disease

Answer 34

• Cause
  
  • Deposits of fatty substances such as cholesterol n saturated fats) on inner surface of coronary arteries (atherosclerosis) -> lumen of arteries narrowed n ^BP ->Blood clot forms in artery -> devs rough inner surface -> Reduced blood flow to heart -> Heart muscle cells receive reduced oxygen for aerobic respiration and glucose supply -> May lead to a heart muscle cell death and heart attack

Question 35

Atherosclerosis

Answer 35

disease where fatty deposits accumulate on inner walls of arteries, narrowing lumen

Question 36

Coronary artery

Answer 36

an artery that branches out of the aorta, sending O2 n nutrients to the heart muscles

Question 37

Heart attack

Answer 37

• Blood supply to the heart muscles can be greatly reduced due to the blockage of the coronary arteries by accumulation of fatty deposits on the inner wall.
• Blood flow to particular part of heart blocked -> receives insufficient O2 n nutrients -> region of heart muscle dies -> fatal as heart X pump blood to various parts of body

Question 38

Risk factors of coronary heart diseases

Answer 38

• Smoking
• Unhealthy diet
• Genetic factors
• Age
• Sedentary lifestyle

Question 39

Prevention of coronary heart diseases

Answer 39

• Healthy diet
• Avoid smoking
• Regular physical exercise

Question 40

Describe and explain the effects of smoking in oxygen transport in humans. [3]

Answer 40

1. Carbon monoxide binds irreversibly to haemoglobin forming carboxyhaemoglobin [1]
2. reduce transport of oxygen in blood [1]
3. less oxygen supplied to tissues for aerobic respiration to release E for normal body functioning. [1]

Question 41

Describe movements of substances between capillaries and cells. [3]

Answer 41

Capillaries bring nutrients and O2, which diffuse from the blood plasma to the tissue fluid and into cells. Waste products and CO2 diffuse out of the cells into the tissue fluid, then into the blood plasma of capillaries,

Question 42

Explain how capillaries r adapted for their function. [4]

Answer 42

1. Capillaries r made of a one-cell thick layer of endothelial cells, minimising the diffusion distance, increasing the rate substances diffuse in and out of capillaries.
2. They branch repeatedly to ^ SA:V, increasing rate of diffusion of substances
3. Endothelium is partially permeable, allowing small substances like glucose and CO2 to diffuse in and out, larger molecules like blood proteins cannot diffuse out.
4. They have very large total cross-sectional SA, lowering blood pressure and slowing blood down to increase time for diffusion to occur.

Question 43

Explain how the blood functions to protect the body against infections.
[3]

Answer 43

Lymphocytes produce antibodies [1] to agglutinate pathogens [1] and
neutralise toxins [1] and the phagocytes engulf and ingest pathogens by phagocytosis. [1]

Question 44

Explain why it is impossible for a person of blood type A to receive B
type blood during blood transfusion. [3]

Answer 44

Blood type A has A antigen on the surface of the RBC, thus the blood
plasma contain B antibodies [1]. Blood type B has B antigen on the surface of the RBC, upon transfusion, the B antibodies in plasma will bind with the transfused B antigen RBCs and cause agglutination. [1]. Agglutination of RBCs will cause blockage in blood vessels resulting in heart attack / stroke / organ failure. [1]