Lecture 7: Blood Vessels - Structure and Function

Question 1

what is the basic arterial vessel wall structure

Answer 1

tunica intima - endothelial cell layer, basement memb, sub endothelial CT layer, internal elastic lamina
tunica media - smooth muscle cells & elastic fibres in concentric layers, external elastic lamina
tunica adventitia - CT blends with surrounding tissue, contain smaller blood vessels in larger arteries = vasa vasorum

Question 2

what is the function of the tunica intima

Answer 2

barrier
prevents plasma membranes escaping
secretes vasoactive mediators

Question 3

what is the function of the tunica media

Answer 3

mechanical strength

contractile power

Question 4

what is the function of the tunica adventitia

Answer 4

tethers vessel to surrounding tissue

Question 5

what is the functional significance of the smooth continuous endothelium

Answer 5

low frictional resistance

Question 6

what is the functional significance of the elastic lamina and elastic fibres?

Answer 6

elasticity during pulsate pressure changes

Question 7

what is the functional significance of the smooth muscle cells

Answer 7

regulate internal calibre of vessel lumen

Question 8

what is the functional significance of the collagen fibres

Answer 8

protection against stresses

Question 9

what are the five functional groups of blood vessels?

Answer 9

1. conducting arteries
2. distributing arteries
3. resistance vessels
4. exchange vessels
5. capacitance vessels

Question 10

list three features of conducting arteries

Answer 10

1. large and thick walled
2. very distendable - lots of elastic
3. most compliant ARTERIES - can stretch and recoil important for the changing blood pressure

Question 11

what are some examples of conducting arteries?

Answer 11

aorta
pulmonary 
brachiocephalic
subclavian
common carotid

Question 12

what is compliance ?

Answer 12

the degree of volume change when distending pressure increases.
C = Delta V/ Delta P
veins are more compliant than arteries

Question 13

why is arterial compliance important?

Answer 13

important in converting pulsative flow from the heart

elastic arteries act as a pressure reservoir, continues driving blood forward during diastole

Question 14

what are two features of distributing arteries

Answer 14

1. muscular - tunica media has more smooth muscle (relative to lumen) than conducing arteries
2. rich sympathetic innervation

Question 15

what is the primary role of the distributing arteries?

Answer 15

conduct flow to the smaller arteries

Question 16

what are some examples of distributing arteries?

Answer 16

femoral artery, internal carotid artery

Question 17

where does the most major fall in blood pressure occur?

Answer 17

over the resistance vessels

Question 18

what are examples of resistance vessels?

Answer 18

arterioles and metarterioles

Question 19

what is the role of the arterioles?

Answer 19

regulate total peripheral resistance, control blood flow to the capillary beds with metarterioles

Question 20

what is the wall structure of the arterioles

Answer 20

tunica intima - fenestrated endothelium
tunica media - 1-2 layers of smooth muscle
tunica adventitia - loose CT

Question 21

what is the role of the metarterioles?

Answer 21

regulate total peripheral resistance, co-op with arterioles to control blood flow to capillary beds

Question 22

what is the wall structure of the metarterioles?

Answer 22

tunica intima - fenestrated endo
tunica media - single intermittent layer of smooth muscle or no smooth muscle
tunica adventitia - not recognised

Question 23

what is resistance?

Answer 23

the opposite of flow
= difference in mean pressure needed to drive one unit of flow.
the largest blood pressure decrease is found in the arterioles vessels, pulsative flow also disappears here – this is where the largest resistance is.

Question 24

describe the rate of blood flow (L/min)

Answer 24

remains the same across all vascular beds

in individual capillary speeds is very slow but same volume is maintained

Question 25

what is TPR?

Answer 25

resistance to flow through the entire systemic circulation

TPR = (mean aortic pressure - Vena cava pressure/ CO)

Question 26

what is CO?

Answer 26

CO = HR x TPR

Question 27

what are some determinants of TPR?

Answer 27

MAP = CO x TPR 
MAP = diastolic pressure e+ 1/3rd pulse pressure

Question 28

what are two features of exchange vessels?

Answer 28

low resistance

high cross sectional area

Question 29

what is the function of exchange vessels?

Answer 29

metabolic exchange takes place across the walls of exchange vessels, CO2, O2 and Metabolites

Question 30

how are capillaries classified

Answer 30

1. position in vascular bed

2. nature of endothelial lining

Question 31

what is the x2 essential components of capillary wall structure

Answer 31

1. thin endothelial layer

2 basement membrame

Question 32

how can the endothelial lining differ

Answer 32

• continuous with thick or thin endothelium = lipid soluble
• fenestrated
• discontinuous = proteins can come through

Question 33

what are sinusoids

Answer 33

exchange vessels
discontinuous endothelial layer and basement membrane
= allow easy interchange of macromolecules and fluid
characteristic of liver and haemopoietic tissue

Question 34

what are post capillary venules

Answer 34

exchange vessels
drain several capillaries
continuous endothelial layer and basement membrane, surrounded by persecutes, no or few SMC
promote migration of WBC due to leaky joins b/w cells

Question 35

what are capacitance vessels?

Answer 35

large volume and low pressure
return blood to heart
includes all muscular venules and veins

Question 36

what is the wall structure of the capacitance vessels?

Answer 36

tunica intima - same as arteries but no internal elastic lamina
tunica media - relatively small amounts of SMC and elastic fibres
usually abundant collagen fibres
no external elastic lamina
tunica adventitia - many large collagen fibres in the CT
often the thickest layer

Question 37

what factors influence venous return?

Answer 37

smooth muscle contraction- induce vasoconstriction
skeletal muscle pump effect
one way valves
thoracic and cardiac pressure: incl pressure gradient between veins and heart

Question 38

valves in the lumen of veins

Answer 38

composed of two cusps
valves present in medium size veins.
opening of pocket directed towards the heart
standing animal, weight bearing limbs extend well below heart, would lead to pooling and excessive filtration bt the valves convert the column of the vein into short segments reducing hydrostatic pressure
–> even blood vol in each segment
valves make sure theres an equal amount of blood in each segment

increase VR prevent back flow and pooling

Question 39

skeletal muscle pump

Answer 39

contraction of the muscles in the limb applies pressures to the veins. promotes movement of blood towards the heart since the valves prevent the movement away from the heart

Question 40

respiratory activity and cardiac suction

Answer 40

mechanism work by increasing pressure gradient between the veins and the heart

Question 41

sympathetically induced vasoconstriction

Answer 41

sympathetically induced vasoconstriction