Topic 5 - The Circulatory System

Question 1

Plasma

Answer 1

The straw-coloured liquid portion of the blood. It carries red blood cells, white blood cells, platelets, digested food products, carbon dioxide, urea, hormones, and heat energy.

Question 2

Platelets

Answer 2

Small fragments of cells that help blood clot.

Question 3

Why blood clotting is important

Answer 3

In a clot, platelets are held together by a mesh of protein called fibrin. Blood clots stop you losing too much blood and prevent microorganisms from entering the wound

Question 4

Red blood cells

Answer 4

Specialised cells which carry oxygen to respiring cells.

Question 5

Red blood cells adaptations

Answer 5

1. Biconcave shape to increase surface area for absorbing and releasing oxygen
2. Contain haemoglobin to bind to oxygen, forming oxyhaemoglobin
3. No nucleus to create space for more haemoglobin to carry more oxygen

Question 6

Artery

Answer 6

Blood vessels that carry blood at a high pressure away from the heart. All arteries carry oxygenated blood except the pulmonary artery.

Question 7

Arteries adaptations

Answer 7

• have thick, muscular walls containing elastic fibres to withstand high pressure of blood pumped by the heart
• narrow lumen to maintain high blood pressure

Question 8

Veins

Answer 8

Blood vessels that carry blood at low pressure towards the heart. All veins carry deoxygenated blood except the pulmonary vein.

Question 9

Veins adaptations

Answer 9

• large lumen reduces resistance to blood flow under low pressure
• valves present to prevent backflow of blood under low pressure

Question 10

Capillaries

Answer 10

The smallest and narrowest blood vessels in the human body. They connect arteries and veins to form a network that allows for the exchange of oxygen, nutrients and waste products between the blood and the body’s cells.

Question 11

Capillaries adaptations

Answer 11

• walls of capillaries and one cell thick to provide a short diffusion distance for substances to easily diffuse in and out
• they have permeable walls so substances can diffuse in and out

Question 12

Coronary heart disease

Answer 12

When the coronary arteries that supply blood to the heart get blocked by layers of fatty material building up. This causes arteries to become narrow, so blood flow is restricted and there’s a lack of oxygen to the heart muscle. This can lead to a heart attack.

Question 13

Risk factors for coronary heart disease

Answer 13

• poor diet - eating more saturated fat increases cholesterol levels, increasing the chances of the buildup of fatty deposits
• smoking - nicotine narrows blood vessels, increasing blood pressure, which causes damage to the inside of coronary arteries due to the excessive force. This makes it more likely for fatty deposits to form.
• inactivity - causes high blood pressure, which can damage lining of arteries, making it more likely for fatty deposits to form

Question 14

Exercise and heart rate

Answer 14

• during exercise, muscle cells respire more rapidly to provide energy for muscle contractions
• increase in respiration means increase in requirement for oxygen and glucose and increase in production of waste products
• heart rate increases to deliver oxygen and glucose to remove waste more frequently
• volume of blood pumped out of heart also increases to deliver bigger quantities of oxygen and glucose

Question 15

Pathway of blood through the heart

Answer 15

• right atrium receives deoxygenated blood from the body through the vena cava
• deoxygenated blood moves to right ventricle, which pumps it to the lungs via the pulmonary artery
• the left atrium receives oxygenated blood from the lungs through the pulmonary vein
• the oxygenated blood moves to the left ventricle, which pumps it out to the whole body via the aorta