The Blood System

Question 1

Draw a labelled diagram to show the internal structure of the heart./ Draw a labelled diagram of the heart showing all four chambers, associated blood vessels and valves. 5 marks SL

6 marks

Answer 1

vena cava
inferior and superior vena cava distinguished
aorta
pulmonary artery
pulmonary vein
left ventricle
right ventricle
left ventricle shown with thicker wall than right ventricle
septum
left atrium
right atrium
coronary artery
two semi-lunar valves
AV valves
bicuspid and tricuspid valves distinguishedleft and right ventricles
left and right atria
atrioventricular valves / bicuspid / mitral and tricuspid valves
semilunar valves
aorta and vena cava
pulmonary artery and pulmonary vein
ventricle thicker than atria
left ventricle wall thicker than right ventricle wall

Question 2

Outline the events that occur within the heart, which cause blood to move around the body.

6 marks

Answer 2

blood is collectred in the atria
blood is pumped from the atria to the ventricles
opened atrio-ventricular valves allow flow from the atria to the ventricles
closed semi-lunar valves prevent backflow from the arteries to the ventricles
blood is pumped out from the ventricles to the arteries
open semi-lunar valves allow flow from ventricles to arteries
closed atrio-ventricular valves prevent backflow to the atria
pressure generated by the heart causes blood to move around the body
pacemaker (SAN) initiates each heartbeat

Question 3

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

9 marks SL

Answer 3

(3 marks maximum for information on arteries.)
- carry blood away from the heart
- have thick walls to withstand high pressure / prevent bursting
- have muslce fibers to generate the pulse / help pump blood / even out blood flow
- have elastic fibers to help generate pulse / allow artery wall to stretch / recoil

(3 marks maximum for information on capillaries.)
- allow exchange of oxygen/carbon dioxide/ nutrients/waste products from tissues/cells
- have a thin wall to allow (rapid) diffusion / movement in / out
- have pores / porous walls to allow phagocytes / tissue fluid to leave
- are narrow so can penetrate all parts of tissues / bigger total surface area

(3 marks maximum for information on veins.)
- carry blood back to the heart / from the tissues
- have thinner walls because the pressure is low / to allow them to be squeezed
- have fewer muscle / elastic fibers because there is no pulse / because pressure is low
- have valves to prevent backflow