7.6- BLOOD VESSELS AND THEIR FUNCTIONS

Question 1

What are the 4 different types of blood vessels?

Answer 1

arteries
arterioles
capillaries
veins

Question 2

What do arteries carry?

Answer 2

blood away from heart + into arterioles

Question 3

What are arterioles?

Answer 3

smaller arteries that control blood flow from arteries to capillaries

Question 4

What are capillaries?

Answer 4

tiny vessels that link arterioles to veins

Question 5

What do veins carry?

Answer 5

blood from capillaries back to heart

Question 6

What is the basic layered structure of arteries, arterioles + veins from outside inwards? (5)

Answer 6

tough fibrous outer layer 
muscle layer 
elastic layer
thin inner lining (endothelium)
lumen

Question 7

What does the tough fibrous outer layer of the basic layered structure of arteries, arterioles + veins do?

Answer 7

resists pressure changes from both within + outside

Question 8

What does the muscular layer of the basic layered structure of arteries, arterioles + veins do?

Answer 8

can contract + so control flow of blood

Question 9

What does the elastic layer of the basic layered structure of arteries, arterioles + veins help do?

Answer 9

helps maintain blood pressure by stretching + springing back (recoiling)

Question 10

What does the thin inner lining (endothelium) of the basic layered structure of arteries, arterioles + veins do?

Answer 10

smooth to reduce friction + thin to allow diffusion

Question 11

What is the lumen of the basic layered structure of arteries, arterioles + veins?

Answer 11

not actually a layer but the central cavity of the blood vessel through which blood flows

Question 12

What differs between the arteries, arterioles + veins?

Answer 12

relative proportion of each layer

Question 13

How is the structure of arterioles different from arteries?

Answer 13

arterioles smaller in diameter + having relatively larger muscle layer + lumen

Question 14

What is the difference in structure of arteries, arterioles + veins related to?

Answer 14

differences in function that each type of vessel performs

Question 15

What is the function of arteries?

Answer 15

transport blood rapidly under high pressure from heart to tissues

Question 16

How is the structure of arteries adapted to their function? (4)

Answer 16

muscle layer thick compared to veins
elastic layer relatively thick compared to veins
overall thickness of wall great
no valves

Question 17

What can smaller arteries do as the muscle later is thick compared to veins?

Answer 17

smaller arteries can be constricted + dilated to control volume of blood passing through them

Question 18

Why is the elastic layer of arteries relatively thick compared to veins?

Answer 18

as it’s important that blood pressure in arteries kept high if blood is to reach extremities of body

Question 19

What happens to the elastic walls of the arteries during systole + diastole?

Answer 19

elastic wall stretched at each beat of heart (systole)

then springs back when heart relaxes (diastole)

Question 20

What does the stretching + recoiling action of the arteries help maintain?

Answer 20

helps maintain high pressure + smooth pressure surges created by beating of heart

Question 21

What does the overall thickness of the wall of arteries being great resist?

Answer 21

resists vessel bursting under pressure

Question 22

Which arteries do have valves? - they’re an exception

Answer 22

arteries leaving the heart

Question 23

Why are there no valves in arteries?

Answer 23

blood under constant high pressure due to heart pumping blood into arteries
so tends not to flow backwards

Question 24

What do arterioles carry?

Answer 24

blood under lower pressure than arteries, from arteries to capillaries

Question 25

What do arterioles control?

Answer 25

control flow of blood between arteries + capillaries

Question 26

What structures of arterioles is related to their function? (2)

Answer 26

muscle layer relatively thicker than in arteries | elastic layer relatively thinner than in arteries

Question 27

What does the contraction of the muscle layer of arterioles allow?

Answer 27

constriction of lumen of arteriole

Question 28

What does the contraction of the muscle layer constricting the lumen of arterioles do?

Answer 28

restricts flow of blood + so control its movement into capillaries that supply the tissue with blood

Question 29

Why is the elastic layer of arterioles relatively thinner than in arteries?

Answer 29

as blood pressure lower

Question 30

What do the veins do?

Answer 30

transport blood slowly, under low pressure, from capillaries in tissues to heart

Question 31

What structures do veins have that are related to its function? (4)

Answer 31

muscle layer relatively thin elastic layer relatively thin overall thickness of wall small valves at intervals throughout

Question 32

Why is the muscle layer of veins relatively thin in comparison to arteries?

Answer 32

as veins carry blood away from tissues + so their constriction + dilation cannot control flow of blood to tissues

Question 33

Why is the elastic layer of veins relatively thin compared to arteries?

Answer 33

as low pressure of blood within veins will not cause them to burst + pressure too low to create recoil action

Question 34

Why is the overall thickness of vein wall small?

Answer 34

as there's no need for thick wall as pressure within veins too low to create any risk of bursting also allows them to be flattened easily aiding flow of blood within them

Question 35

Why are there valves at intervals throughout veins?

Answer 35

to ensure blood doesn't flow backwards, which it might otherwise do as pressure is so low

Question 36

What happens to veins when muscles contract? (valves at intervals throughout veins)

Answer 36

veins compressed, pressuring blood within them | valves ensure this pressure directs blood in one direction only: towards heart

Question 37

What is the function of the capillaries?

Answer 37

exchange metabolic materials i.e. oxygen, carbon dioxide + glucose between blood and cells of body

Question 38

How is the flow of blood in capillaries in comparison to the other vessels?

Answer 38

flow of blood in capillaries much slower

Question 39

What does the flow of blood in capillaries being much slower allow?

Answer 39

allows more time for exchange of materials

Question 40

How is the structure of the capillaries related to their function? (5)

Answer 40

their walls consist mostly of lining layer numerous + highly branched narrow diameter lumen so narrow spaces between lining (endothelial) cells

Question 41

What does the capillary walls consisting mostly of lining layer make them?

Answer 41

makes them extremely thin, so distance over which diffusion happens is short

Question 42

What does the distance over which diffusion happens being short allow? (capillaries- walls consisting mostly of lining layer)

Answer 42

allows for diffusion of material between blood + cells

Question 43

What does the capillaries being numerous + highly branched provide?

Answer 43

provide large SA for exchange

Question 44

What does the capillaries having a narrow diameter mean?

Answer 44

permeate (spread throughout) tissues, which means that no cells far from capillary + there's short diffusion pathway

Question 45

What happens as the lumen of the capillaries are so narrow?

Answer 45

red blood cells squeezed flat against the side of capillary

Question 46

What does the lumen of capillaries being narrow and red blood cells being squeezed flat against the side of capillary mean?

Answer 46

brings red blood cells even closer to cells to which they supply oxygen reduces diffusion distance

Question 47

What do the spaces between the lining (endothelial) cells of the capillary allow?

Answer 47

allow white blood cells to escape to deal with infections within tissues

Question 48

Although capillaries are small, what can they not do?

Answer 48

cannot serve every single cell directly

Question 49

Where is the final journey of metabolic material made in?

Answer 49

liquid solution that bathes the tissues called tissue fluid

Question 50

What is tissue fluid?

Answer 50

watery liquid that contains glucose, amino acids, fatty acids, ions in solution + oxygen

Question 51

What does tissue fluid supply?

Answer 51

supplies substances in it to tissues

Question 52

What does tissue fluid receive from tissues?

Answer 52

receives carbon dioxide + other waste materials from tissues

Question 53

What is tissue fluid the means of?

Answer 53

means by which materials exchanged between blood + cells, and, as such, bathes all cells of body

Question 54

What is tissue fluid formed from?

Answer 54

from blood plasma

Question 55

What is the composition of blood plasma controlled by?

Answer 55

various homeostatic systems

Question 56

What sort of environment does tissue fluid provide?

Answer 56

mostly constant environment for cells it surrounds

Question 57

Where does blood pumped by heart pass along? (formation of tissue fluid)

Answer 57

arteries, then narrower arterioles + finally even narrower capillaries

Question 58

What pressure does the pumping of the heart create? (formation of tissue fluid)

Answer 58

hydrostatic pressure at arterial end of capillaries

Question 59

What does the hydrostatic pressure at the arterial end of the capillaries cause? (formation of tissue fluid)

Answer 59

cause tissue fluid to move out of blood plasma

Question 60

What factors is the outward pressure opposed by? (2) (formation of tissue fluid)

Answer 60

hydrostatic pressure of tissue fluid outside capillaries, which resists outward movement of liquid lower water potential of blood, due to plasma proteins, that causes water to move back into blood within the capillaries

Question 61

What is the combined effect of all the forces to create? (formation of tissue fluid)

Answer 61

to create overall pressure that pushes tissue fluid out of capillaries at arterial end

Question 62

What is the overall pressure of the combined forces only enough to do? (formation of tissue fluid)

Answer 62

only enough to force small molecules out of capillaries leaving all cells + proteins in blood as these are too large to cross the membrane

Question 63

What is the type of filtration of small molecules out of capillaries leaving all cells + proteins in blood as these are too large to cross the membrane under pressure called?

Answer 63

ultrafiltration

Question 64

What happens to tissue fluid once it has exchanged metabolic materials with the cells it bathes? (return of tissue fluid to circulatory system)

Answer 64

it's returned to circulatory system

Question 65

How does more tissue fluid return to the blood plasma? (return of tissue fluid to circulatory system)

Answer 65

directly via capillaries

Question 66

Return of tissue fluid to blood plasma directly via capillaries: #1 hydrostatic pressure

Answer 66

loss of tissue fluid from capillaries reduce hydrostatic pressure in them

Question 67

Return of tissue fluid to blood plasma directly via capillaries: #2 venous end

Answer 67

by the time blood has reached venous end on capillary network its hydrostatic pressure usually lower than that of tissue fluid outside it

Question 68

Return of tissue fluid to blood plasma directly via capillaries: #3 tissue fluid

Answer 68

tissue fluid forced back into capillaries by higher hydrostatic pressure outside them

Question 69

Return of tissue fluid to blood plasma directly via capillaries: #4 what does the plasma still contain

Answer 69

plasma has lost water + still contains proteins | so has lower water potential than tissue fluid

Question 70

Return of tissue fluid to blood plasma directly via capillaries: #5 what happens to water

Answer 70

water leaves tissue by osmosis down water potential gradient

Question 71

Cab all the tissue fluid return to the capillaries?

Answer 71

no

Question 72

Where is the remainder tissue fluid carried back by?

Answer 72

via lymphatic system

Question 73

What is the lymphatic system?

Answer 73

system of vessels that begin in tissues initially resemble capillaries (except thy have dead ends), but gradually merge into larger vessels that from network throughout body

Question 74

What do the larger vessels of the lymphatic system do?

Answer 74

drain their contents back into bloodstream via two ducts that join veins close to heart

Question 75

Are the contents of the lymphatic system (lymph) moved by the pumping of the heart?

Answer 75

no

Question 76

What is the contents of the lymphatic system (lymph) moved by? (2)

Answer 76

hydrostatic pressure of tissue fluid that has left the capillaries contraction of body muscles that squeeze lymph vessels

Question 77

What do the valves in the lymph vessels ensure?

Answer 77

that fluid inside them moved away from tissues in direction of heart