The Circulatory System 4

Question 1

what do blood vessels do?

Answer 1

direct flow of blood from heart to organs + tissues and back to the heart

Question 2

what do blood vessels consist of?

Answer 2

• arteries
• arterioles
• capillaries
• venules
• veins

Question 3

arteries

Answer 3

carry blood away from heart to tissues

Question 4

arterioles

Answer 4

smaller branches of arteries with organs

Question 5

capillaries

Answer 5

smaller branches of arterioles within organs; facilitate exchanges between blood and surrounding cells

Question 6

venules

Answer 6

formed when capillaries re-join; return blood to heart

Question 7

veins

Answer 7

formed when venues re-join; return blood to heart

Question 8

the walls of blood vessels are composed of up to 3 tunics. what are these?

Answer 8

• tunic externa (adventitia)
• tunic media
• tunic interna (intima)

Question 9

tunic externa (adventitia)

Answer 9

outer layer comprised of connective tissue elastin fibres

Question 10

tunic media

Answer 10

middle layer composed of smooth muscle

Question 11

tunic interna (intima)

Answer 11

• innermost lining of squamous endothelium
• basement membrane
• layer of elastin

Question 12

what are the main functions of the arteries?

Answer 12

• serve as rapid-transit conduits for blood from heart to organs
• act as pressure reservoirs
• prov driving force for blood during diastole

Question 13

what are the 2 main types of arteries?

Answer 13

• elastic arteries (aorta + p.artery)
• muscular arteries (femoral + coronary arteries)

Question 14

elastic arteries

Answer 14

• numerous layers of elastin fibres in vessel wall
• expand when pressure of blood rises + recoils

Question 15

muscular arteries

Answer 15

• less elastic but thicker layer of smooth muscle
• diameter changes slightly as BP rises + falls

Question 16

what are arterioles?

Answer 16

smaller branches of arteries within organs

Question 17

what do arterioles contain the highest % of?

Answer 17

smooth muscle

Question 18

arterioles are the major ….. vessels

Answer 18

major

Question 19

vessel radius supplying individual organs can be adjusted independently. give examples of this?

Answer 19

• distribute cardiac output among systemic organs
• depending on body momentary needs
• helps regulate arterial blood pressure

Question 20

control of tone of arterioles is mediated through what…

Answer 20

nervous + chemical mechanisms

Question 21

what does a large pressure drop facilitate blood flow to?

Answer 21

organs

Question 22

what is vasoconstriction caused by?

Answer 22

• inc in myogenic activity
• inc in oxygen (O2)
• dec in CO2
• inc in endothelin
• inc in sympathetic stimulation vasopressin, angiotensin II

Question 23

what is vasodilation caused by?

Answer 23

• dec in myogenic activity
• dec in O2
• inc in CO2
• inc in nitric oxide
• dec in sympathetic stimulation histamine release

Question 24

what are capillaries?

Answer 24

smaller + dense branches off arterioles + metarterioles within organs

Question 25

what do precapillary sphincters regulate?

Answer 25

blood flow

Question 26

there are .. main types of capillaries depending on … of pores

Answer 26

3 size

Question 27

exchange of materials largely occurs via what...

Answer 27

diffusion

Question 28

what do the very thin walls of capillaries consist of?

Answer 28

single layer of flat endothelial cell + thin basement membrane

Question 29

walls of capillaries are perforated by water filled pores. what does this permit?

Answer 29

passage of small water-soluble substances

Question 30

what are the 3 main types of capillaries?

Answer 30

- continuous - fenestrated - discontinuous (sinusoidal)

Question 31

continuous

Answer 31

- endothelial cells = continuous/closely joined - narrow intercellular pores (~4nm) permit passage of molecules - skeletal + cardiac muscle, lungs + adipose tissue

Question 32

fenestrated

Answer 32

- have larger holes (20-100nm) in addition to narrow pores - have greater permeability + rapid exchange - kidneys, intestine + endocrine glands

Question 33

discontinuous (sinusoidal)

Answer 33

- endothelial cells = discontinuous —\> v large pores + leaky capillaries - liver, spleen + bone marrow

Question 34

what does transcytosis bring?

Answer 34

proteins and macromolecules across endothelium

Question 35

what are the 2 mechanisms of capillary exchange between blood + surrounding tissues?

Answer 35

- passive diffusion - bulk flow

Question 36

what is passive diffusion?

Answer 36

movement of solutes down conc gradient

Question 37

what is bulk flow?

Answer 37

ultrafiltration + reabsorption of protein-free plasma

Question 38

what are the determinants of bulk flow?

Answer 38

- capillary blood pressure (Pc) - plasma-colloid osmotic pressure (πp) - interstitial fluid hydrostatic pressure (Pif) - interstitial fluid colloid osmotic pressure (πif)

Question 39

formula for net exchange pressure?

Answer 39

Question 40

what is the venous system?

Answer 40

low resistance system that returns blood from tissue to the heart

Question 41

what does the venous system comprise of?

Answer 41

- venules - small veins - large, systemic veins

Question 42

systemic veins

Answer 42

- large radius --\> low resistance to flow - thing walls with little smooth muscle/elastin --\> high distensibility + little elastic recoil - serve as blood reservoir/capacitance vessels - one-way valves ensure blood flow to heart

Question 43

what does an increase in venous return lead to?

Answer 43

- inc in end-diastolic volume - inc in stroke vol - inc in cardiac output

Question 44

what are the short term factors that facilitate an increase in venous return?

Answer 44

- inc in blood volume - inc in sympathetic vasoconstrictor activity - respiratory pump - dec pressure in chest veins --\> inc in pressure gradient - skeletal muscle pump - inc in venous pressure --\> inc in pressure gradient - cardiac suction effect - dec pressure in heart --\> inc in pressure gradient - pressure imparted to blood by cardiac contraction - inc in venous pressure --\> inc in pressure gradient

Question 45

what are the relative thickness layers in endothelium walls?

Answer 45

all blood vessels same thickness

Question 46

what are the relative thickness layers in elastic fibre walls?

Answer 46

arteries have greatest thickness then veins

Question 47

what are the relative thickness layers in smooth muscle walls?

Answer 47

arteries have greatest thickness followed by arterioles AND veins

Question 48

what are the relative thickness layers of collagen fibre walls?

Answer 48

arteries have greatest thickness followed by veins and then arterioles