7. Transport in Humans

Question 1

function of red blood cells (2)

Answer 1

1. transport oxygen that diffuses from the lung into the blood and binds reversibly
   with haemoglobin in red blood cells to form oxyhaemoglobin.
2. When blood is transported to oxygen-poor respiring tissues,
   oxyhaemoglobin releases its oxygen which then diffuses into tissue cells

Question 2

function of plasma (6)

Answer 2

Soluble plasma proteins such as fibrinogen, prothrombin and
antibodies. Fibrinogen and prothrombin play an important part
in the clotting of blood. These proteins are made in the lever.
Antibodies help to fight diseases.
• Dissolved mineral salts, for example, hydrogencarbonates,
chlorides, sulfates and phosphates of calcium, sodium and
potassium. All these occur as ions in the plasma. Calcium is
essential for blood clotting.
• Food substances, for example, glucose, amino acids, fats and
vitamins.
• Excretory products, for example, urea, uric acid and creatinine.
Carbon dioxide is present as hydrogencarbonate ions.
• Hormones, for example, insulin.
• Vitamins

Question 3

function of white blood cells

Answer 3

have immune functions and tissue rejections

Question 4

function of platelets (3)

Answer 4

• Blood platelets or thrombocytes are not true cells.
- They have no nucleus and they are membrane-bound cell fragments
• They play a part in the blood clotting

Question 5

Structure of Arteries and its functions (2,3 tep)

Answer 5

ARTERY
Function:
• Arteries are blood vessels which
carry blood away from the heart,
thus need to withstand the high
pressure of blood pumped out of the
heart.
• All arteries carry oxygenated blood
with the exception of the pulmonary
arteries.
Structure and adaptations:
• Thick, muscular and elastic walls
• Thick walls allow arteries to
withstand immense pressure of
blood that was just pumped out of
the heart
• Elasticity of wall allows arteries to
stretch and recoil under high
pressure and push blood along
arteries

Question 6

Structure of veins and its functions (1,3 tlv)

Answer 6

VEINS
Function:
• All veins carry deoxygenated blood
with the exception of the pulmonary
veins.
Structure and adaptations:
• Middle wall contains much less
smooth muscle and elastic fibres.
Hence they are not as thick,
muscular or elastic as arteries as the
blood pressure is lower
• Large lumen offer low resistance to
blood flow, blood can flow smoothly
back to the heart
• Semi lunar vales are present which
will close to prevent backflow of
blood to ensure flow of blood in one
direction.

Question 7

Structure of capillaries and its functions (2,3)

Answer 7

Function:
• Allow exchange of nutrients and waste materials between blood and tissue fluid
• gaseous exchange
Structure and Adaptations:
• The wall of capillary is single layer of endothelial cells. One cell thick wall allows shorter distance for oxygen and food
substances to diffuse from and waste products to diffuse from
• Extensive network of blood capillaries surrounding the cells maintains steep concentration gradient to ensure efficient
exchange of materials with tissue cells
• The extensive branching increases the total cross-sectional area of the vessels, lowering the blood pressure in the
capillaries and hence slowing down blood flow, giving more time for the exchange of substances

Question 8

Name the main blood vessels to and from the heart, liver and kidney (8)

Answer 8

1. pulmonary vein
2. pulmonary artery
3. aorta
4. hepatic vein
5. hepatic artery
6. hepatic portal vein
7. renal vein
8. renal artery

Question 9

describe the structure and function of the heart in terms of muscular contraction and the working of
valves
- path of blood (2 directions)
- structure of heart (5)

Answer 9

deoxygenated blood (inferior/superior vena cava → right atrium →
right ventricle → pulmonary artery) →
(lung → pulmonary vein → left atrium → left
ventricle → aorta → other parts of bodies) oxygenated blood

1. atrium
2. ventricle
3. median septum
4. atrioventricular valves
5. semi lunar valves

Question 10

describe coronary heart disease in terms of the occlusion of coronary arteries
- state the 2 diseases
- describe what happens (4,3)

Answer 10

The coronary arteries branch out from the aorta to provide oxygen and
nutrients to the heart muscles
1. Atherosclerosis is the buildup of cholesterol and fatty deposits in the
coronary artery wall
• the buildup of cholesterol and fatty deposits in the coronary artery wall
• The deposition of plaque causes narrowing or occlusion of coronary artery
• Narrow lumen causes angina (chest pain) or discomfort in the area of heart
that does not get suficient blood, hence less oxygen and nutrients
• The narrowing of the lumen of the arteries also causes an increase in blood
pressure. This causes arteries to develop rough linings, which increases the
likelihood of formation of blood clots inside the arteries. This is known as
thrombosis.
2. Blood clots complete block coronary artery
• When the coronary arteries are completely blocked, blood supply to part of
the heart muscle is completely cut off.
• Do not get glucose and oxygen
• The affected area of heart dies, affecting the heart’s ability to pump and lead to
heart failure and heart attack

Question 11

function of atrium

Answer 11

• upper chambers of the heart, with relatively thin walls. They collect blood
returning to the heart and pump it into the ventricles

Question 12

function of ventricle (3)

Answer 12

• lower chambers of the heart
• The ventricles have thick, muscular walls compared to atrium.
• The left ventricle has thicker walls than the right ventricle, as it has to
pump blood to the rest of the body, while right ventricle pumps blood to
the lung

Question 13

function of median septum (3)

Answer 13

• muscular wall that separates right and left sides of the heart
• The median septum prevents the mixing of deoxygenated blood in the
right side with the oxygenated blood in the left side to ensure maximum
amount of oxygen is transported to the body
• Mixing will reduce the amount of oxygen carried to the tissue cells

Question 14

function of atrioventricular valves (3)

Answer 14

• Between the right atrium and ventricle is the tricuspid valve which consists
of three flaps attached to the walls of the right ventricle by cord-like
tendons called cordae tendineae.
• Between the left atrium and left ventricle is the bicuspid valve which
consists of two flaps, also attached by cordae tendineae.
• Prevent back flow of blood from ventricles to atrium

Question 15

function of semi lunar valves (3)

Answer 15

• Aortic valve on left side, pulmonary valve on right side of the heart
• Located at the start of the aorta and pulmonary arteries
• Prevent back flow of blood from arteries back to ventricles

Question 16

describe what happens during pumping of blood in the heart (7)

Answer 16

1. Atrial systole: The atria contract causing a rapid but relatively small
   pressure increase, which pumps blood from the atria to the
   ventricles, through the open atrioventricular valves.
2. Ventricular Systole: The ventricles contract and the atrioventricular
   valves close to prevent backflow of the blood into the atria. This
   produces the ‘lub’ sound of the heartbeat.
3. Atrial diastole: While the ventricles are contracting, the atria relax.
4. The pressure in the ventricles increases and becomes higher than
   that of aorta and pulmonary artery, causing the semi-lunar valves to
   open. Blood flows from the ventricles into the arteries.
5. Ventricular diastole: The ventricles relax causing drop in pressure,
   causing semi-lunar valves to close to prevent backflow of the blood
   into the ventricle. This produces the ‘dub’ sound of the heartbeat.
6. Pressure in the ventricles eventually drops below the pressure in the
   atria so the atrioventricular valves open.
7. Pressure in the ventricles will increase again when blood from atria
   “Lub” “Dub” enters the ventricles, and the cycle repeats

Question 17

list the possible
causes, such as diet, stress, smoking, and the possible preventative measure (3,4)

Answer 17

Factors that contribute to atherosclerosis include:
(a) High intake of cholesterol and saturated fats: promote deposition of
plaque along artery
(b) Stress: promote the buildup of plaque deposits in the arteries
(c) Smoking: Nicotine in cigarette increases blood pressure and carbon
monoxide reduces oxygen carrying capacity of red blood cell
Preventive measures include:
(a) Healthy diet: Reduce cholesterol and saturated fats, substitute with
polyunsaturated plant fats
(b) Not smoking
(c) Exercising: It strengthens the heart and maintains the elasticity of the
arterial walls.
(d) Stress management: reduce high blood pressure