blood vessels

Question 1

describe the role of elastic fibres in blood vessels

Answer 1

composed of elastin - can stretch and recoil to provide flexibility

Question 2

describe the role of smooth muscle in blood vessels

Answer 2

contracts or relaxes to change lumen size

Question 3

describe the role of collagen in blood vessels

Answer 3

provides structural support to maintain shape and volume of vessel

Question 4

what is the function of arteries?

Answer 4

carry oxygenated blood away from the heart to the tissues of the blood

Question 5

what is the function of the pulmonary artery?

Answer 5

carries deoxygenated blood from heart to the lungs

Question 6

describe the role of elastic fibres in arteries

Answer 6

enable them to withstand force of pumping blood so can take larger blood volume

Question 7

why are elastic fibres important to maintain continuous blood flow?

Answer 7

the ability to recoil evens out pumping blood surges - creates continuous flow

Question 8

describe the difference between arteries and arterioles

Answer 8

arterioles: more smooth muscle, less elastin - can constrict/dilate to control blood flow to organs

Question 9

describe vasoconstriction

Answer 9

smooth muscle contracts, the vessel constricts to prevent blood flowing into a capillary bed

Question 10

describe vasodilation

Answer 10

when smooth muscle relaxes, vessel dilates so blood is able to flow into capillary bed

Question 11

state the average lumen sizes of the aorta, arteries and arterioles

Answer 11

• aorta: 2.5cm
• artery: 0.4cm
• arteriole: 30 micrometers

Question 12

describe capillary

Answer 12

microscopic blood vessels that link arterioles with venules

Question 13

what is the lumen size of a capillary

Answer 13

10 micrometers

Question 14

how do gases exchange through capillary walls?

Answer 14

through gaps in endothelial cells making up capillary walls - substances pass out into fluid surrounding the cells

Question 15

what are 3 adaptations of capillaries?

Answer 15

• provide large surface area for diffusion
• cross-sectional area of capillaries is greater than arteriole supplying them - rate of blood flow falls giving more time for gas exchange
• 1 endothelial cell thick

Question 16

describe the role of veins

Answer 16

carry deoxygenated blood away from cells towards heart

Question 17

describe the role of the pulmonary vein

Answer 17

carry oxygenated blood from the lungs to the heart

Question 18

what are 2 major veins in the heart?

Answer 18

• inferior vena cava - from lower body
• superior vena cava - from head

Question 19

why do veins not have a pulse?

Answer 19

surges from heart pumping are lost as blood passes through capillaries

Question 20

what % of blood volume is present in the veins at any given time?

Answer 20

60%

Question 21

describe the structure of the veins

Answer 21

• walls contain collagen and little elastic fibres
• wide lumen, smooth, thin lining (endothelium) so blood flows through easily

Question 22

what are the average lumen sizes of a large vein, medium vein and venule?

Answer 22

• large vein: >1cm
• medium vein: <1cm
• venule: 0.1mm

Question 23

what adaptations do veins have that allow blood to flow against gravity?

Answer 23

• one-way valves at intervals - flaps / infoldings of inner lining open so blood can pass through, if blood starts to flow backwards, valves close
• veins run between big, active muscles so when they contract, blood is forced towards the heart
• breathing movements of the chest act as a pump - pressure changes and squeezing action moves blood in chest/abdomen towards the heart

Question 24

state the chronological order of the blood vessels

Answer 24

arteries –> arterioles –> capillaries –> venules –> veins

Question 25

why are visible blood vessels likely to be veins?

Answer 25

• thick walls allow them to distend / bulge
• large lumen as contains large volume of slow moving blood
• found closer to skin surface than arteries

Question 26

describe the structure of arteries