6.2: The Transportation system

Question 1

State that coronary arteries supply heart muscle with oxygen and nutrients.

Answer 1

State

Question 2

Explain the action of the heart in terms of collecting blood and pumping blood

Answer 2

1. Blood returning from all parts of the body (except lungs) enter the right atrium via the vena cava - this blood is deoxygenated.
2. The blood passes from the right atrium to the right ventricle and then via the pulmonary artery to the lungs- where blood is reoxygenated.
3. The blood returns to the left atrium via the pulmonary vein and passes through the left ventricle to the aorta, where it is pumped around the body.

Question 3

Explain the action of the heart in terms of opening and closing valves.

Answer 3

The heart valves maintain the one-way flow of blood:

• When the atria contract, atrioventricular valves open
• Blood flows from the atria and into the ventricles
• When the ventricles contract, the Atrioventricular valves close and semilunar valves open
• This forces blood out of the ventricles and into the artieries
• As pressure rises, the semilunar valves close, ensuring the one-way flow of blood.

Question 4

Outline the control of the heartbeat

Answer 4

1. The contraction of the heart is myogenic, meaning the signal for cardial contraction arises within the heart muscle itself.
2. The pacemaker is under control from the brain, specifically the medulla and speeds up or slows down the heartbeat based upon the action taken in the brain using neurotransmitters.
3. Adrenaline speeds up the heart rate by releasing a chemical hormone into the blood and signalling the pacemaker.

Question 5

Explain the relationship between the structure and function of arteries, capillaries and veins.

Answer 5

Arteries:

• Thick outer layer of longitudinal collagen and elastic fibres prevents leaks and bulges.
• Thick wall withstands high blood pressure.
• Thick layers of Circular elastic fibres and muscle fibres to help pump blood.
• Narrow lumen to maintain high blood pressure.

Veins:

• Thin layer with few circular elastic fibres and muscle fibres as blood does not flow in pulses.
• Thin walls so that nearby muscles can help push blood towards the heart.
• Thin outer layer of longitudinal collagen and elastic fibres as pressure is low.
• Wide lumen to accommodate the slow flowing blood.

Capillaries:

• Wall is one cell layer thick so distance for diffusion is small.
• Pores allow plasma to leak out and form tissue fluid. Phagocytes can also pass through pores.
• Very narrow lumen so that many can fit in a small space.

Question 6

Blood is composed of:

Answer 6

Plasma (fluid), Erythrocytes (red blood cells), Leukocytes (white blood cells) such as phagocytes and lymphocytes, platelets (blood clotting).

Question 7

The following are transported by blood:

Answer 7

Nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat.