Blood Vessels

Question 1

What are the different components that are utilised in some blood vessels? (3)

Answer 1

• Elastic fibres - composed of elastin and can stretch/recoil, provides flexibility
• Smooth muscle - Contracts/relaxes to change size of lumen
• Collagen - Provides structural support to maintain shape and volume of vessel

Question 2

What kind of blood do arteries carry? Where do they take the blood from and to? (3)

Answer 2

• Carry oxygenated blood EXCEPT pulmonary artery
• Heart to the body
• Pulmonary carries from heart to lungs

Question 3

What is the structure of arteries? (2)

Answer 3

• Endothelium, elastic layer, muscle layer, tough outer layer (collagen)
• Elastic fibres allow them to withstand the force of the blood and stretch to take larger blood volume - gives continuous flow

Question 4

What are arterioles and their structure? (5)

Answer 4

• Link arteries to capillaries
• Have more smooth muscle and less elastin
• Little pulse surge but can constrict/dilate to control blood flow to individual organs
• Smooth muscle contracts to prevent blood flowing into a capillary bed (vasoconstriction)
• Can also relax to allow blood to flow through capillary bed (vasodilation)

Question 5

What are capillaries and what is their structure? (3)

Answer 5

• Join the arterioles to venules
• Single cell thick - only capillary wall
• Allow diffusion to take place

Question 6

How are capillaries adapted for their function? (3)

Answer 6

• Large SA:V to maximise diffusion into and out of blood
• Cross-sectional are is smaller than arterioles - reduce pressure and blood flow - slows blood so that there is enough time for diffusion
• One cell thick - reduced diffusion pathway

Question 7

What kind of blood do veins carry? Where do they take the blood to and from? (4)

Answer 7

• Carry deoxygenated blood EXCEPT pulmonary vein and the umbilical vein
• From body cells to the heart
• Pulmonary carries oxygenated blood from lungs to heart
• Umbilical vein carries oxygenated blood from placenta to fetus

Question 8

What are venules and their structure? (2)

Answer 8

• Very small veins that connect capillaries to veins

- Similar structure to arterioles, but generally just increasing the lumen for blood to be carried to the heart

Question 9

What is the structure of veins? (5)

Answer 9

• Endothelium, elastic layer, smooth muscle, tough outer layer
• No pulse
• Low pressure compared to arteries
• Have valves to prevent back-flow of blood
• Wide lumen, smooth lining to let blood flow easily

Question 10

Why do veins have valves? (2)

Answer 10

• Low pressure

- Effect of gravity on blood

Question 11

How do valves work? (2)

Answer 11

• When the blood moves forward, the valve opens to let blood through
• When blood moves backwards, valve closes to prevent backwards movement

Question 12

How else do we prevent backflow? (2)

Answer 12

• Muscle contraction squeezes veins, forcing blood towards the heart
• Breathing movements of chest as a pump, squeezing the veins and forcing blood to move