Circulatory system (CVS)

Question 1

Why is a circulatory system necessary?

Answer 1

to meet metabolic needs
- it allows fast convection system circulating fluids between surfaces

• unicellular organisms using simple diffusion & convection

Question 2

Why is a circulatory system required (for intracellular vs extracellular)?

Answer 2

Maintains steep IC:EC concentration gradient to deliver nutrients/remove wastes from CENTRALLY LOCATED CELLS

Question 3

What is the primary function of the circulatory system?

Answer 3

distribution of gases/molecules (nutrition, growth & repair)

Question 4

What are the secondary functions of circulatory system (CVS)?

Answer 4

• fast chemical singalling - hormones
• dissipation of heat brings blood to the surface
• mediates inflammatory and host defence responses to invading microbes

Question 5

What are the 3 functional parts of the CVS?

Answer 5

PUMP (heart) - maintains pressure
FLUID (blood) - dissolves substances
SET OF CONTAINERS (blood vessels)

Question 6

What are the 3 types of blood vessels?

Answer 6

• arteries
• capillaries
• veins

Question 7

What can lead to a change in demand which requires regulation?

Answer 7

• sleep/awake
• body position /intrathoracic pressure
• rest/exercise, acceleration/deceleration HR (heart rate)
• digestion - a lot of blood diverted towards gastrointestinal tract
• emotional stress, thermal stress

Question 8

What % of blood goes constantly to the cerebrum?

Answer 8

15%

Question 9

In what way is the heart is a dual pump?

Answer 9

the heart pump in two serial circuits

Question 10

What type of circulation is the left heart?

Answer 10

systematic circulation

Question 11

Where can capillary beds in series be found?

Answer 11

kidneys

Question 12

Where can capillary beds be found in parallel & series?

Answer 12

spleen, intestine & liver

Question 13

What type of circulation is the right heart?

Answer 13

pulmonary circulation

Question 14

What is the name of the arterial system?

Answer 14

the distribution system (high pressure)

Question 15

What is the name of the capillary system?

Answer 15

diffusion & filtration system

Question 16

What is the name of the venal system?

Answer 16

collection system (reservoir) - low pressure

Question 17

What is bifocation?

Answer 17

the separation of blood vessels (e.g. arteries in arterioles - microcirculation not just capillaries

Question 18

How many capillaries are there?

Answer 18

40 billion

Question 19

What is the cross-sectional area of aorta?

Answer 19

4cm^2

Question 20

What is the cross-sectional area of capillaries?

Answer 20

2.8 x 10^-7 cm^2

Question 21

What is the cross-sectional area of vena cava?

Answer 21

6cm^2

Question 22

What is the aggregate cross sectional area of the aorta?

Answer 22

4cm^2

Question 23

What is the aggregate cross sectional area of capillaries?

Answer 23

2827 cm^2

Question 24

What is the aggregate cross sectional area of the vena cava?

Answer 24

6cm ^2

Question 25

What is the mean velocity of the aorta?

Answer 25

21 cm/s

Question 26

What is the mean velocity of capillaries?

Answer 26

0.03 cm/s

Question 27

What is the mean velocity of the vena cava?

Answer 27

14 cm/s

Question 28

What is the radius of the largest & smallest vessel?

Answer 28

1.1cm - 3um

Question 29

What is the larger - combined cross-section area of daughter vessels or parent vessel?

Answer 29

combined cross-section area of daughter vessels

Question 30

What are the 4 'building blocks' in vascular wall?

Answer 30

- endothelial cells - elastin fibres - collagen fibres - tough protein - maintains integrity - (vascular) Smooth-muscle cells (VSMC)

Question 31

What are the 3 layers of blood vessel walls?

Answer 31

- intima (tunica interna) - media (tunica media) - adventitia (tunica externa)

Question 32

What is the only intimal layer resting on a basement membrane?

Answer 32

capillaries

Question 33

Why does an aorta have higher levels of elastic fibres?

Answer 33

allows aorta to accommodate for the high pressure generated from the heart

Question 34

Why does the medium artery have higher levels of smooth muscle than the aorta?

Answer 34

smooth muscle is needed for contraction, which is needed more in the smaller vessels

Question 35

Why does the aorta have high levels of collagen?

Answer 35

to maintain the integrity of the vessel

Question 36

Why do veins have high collagen levels?

Answer 36

due to veins containing blood under low pressure, therefore loss of integrity could be fatal

Question 37

Why is it useful for large arteries to have high compliance?

Answer 37

prevents tearing, and enables vessels to cope with peak ejection pressures. The recoil of elastic fibres forces blood to move even the ventricles relaxed - maintains pressure

Question 38

Why is useful for medium-sized arteries to have lots of smooth muscle cells (VSMC)?

Answer 38

allows for greater vasoconstriction/dilation to adjust blood flow rate - partial contraction always occurring (not either relaxed or contracting)

Question 39

What are metaterioles?

Answer 39

Terminal regions (network shortcut)

Question 40

Why are arterioles useful?

Answer 40

smooth muscle enables blood flow regulation to capillary networks - regulated microcirculation

Question 41

What % of capillary beds are open at any one time?

Answer 41

10-25%

Question 42

Why are postcapillary venules porous?

Answer 42

act as exchange sites for nutrients & waste

Question 43

Why is useful for muscular venules to have a thin smooth muscle cell layer?

Answer 43

thin walls allow for expansion - excellent reservoirs for blood

Question 44

What is the purpose of one-way valves?

Answer 44

prevent back flow of blood (facilitates the movement of blood towards the heart)

Question 45

What condition can result from defective, leaky valves that allow back flow of blood?

Answer 45

varicose veins

Question 46

Why can the expansion of a vein wall lead to varicose veins?

Answer 46

allows for blood accumulation in the pockets created, due to back-flow and pooling of the blood

Question 47

What is the function of the CVS?

Answer 47

maintain sustainable environment for tissues

Question 48

What is the principle site of exchange in the CVS?

Answer 48

principal exchange site

Question 49

What substances are exchanged at capillaries?

Answer 49

- gases - e.g. oxygen - water - nutrients - waste products

Question 50

What additional functions can capillaries serve?

Answer 50

- glomerular filtrate - skin temperature regulation - hormone delivery - platelet delivery

Question 51

What 2 things are capillaries composed of?

Answer 51

endothelial cells & basement membrane

Question 52

What are the 3 groups that capillaries could be, based on their leakiness?

Answer 52

- continuous capillary (not leaky) - fenestrated capillary (partly leaky) - sinusoidal (discontinuous) capillary (very leaky)

Question 53

What influences the level of fenestration which capillaries have around the body?

Answer 53

The function of the capillaries in that area

Question 54

What are the Starling forces which drives fluid transfer across capillary walls?

Answer 54

hydrostatic pressure & osmotic pressure

Question 55

What makes up oncotic fluid?

Answer 55

colloid osmotic pressure (oncotic pressure), is due to serum proteins (albumin - protein most prevalent in blood)

Question 56

What is the Starling's forces equation?

Answer 56

Jv = Kf [Pc - Pi] - [pieC - pieI] fluid movement = hydraulic conductance x [capillary hydrostatic pressure - interstitial hydrostatic pressure] - [ (pie x capillary oncotic pressure) - (pie x interstitial oncotic pressure)]

Question 57

Why does capillary hydrostatic pressure decline along the length of capillary through fluid filtration?

Answer 57

As water is lost, there is less plasma, leading a reduction in pressure.

Question 58

By how many litres does arteriole filtration exceed venular absorption in interstitium?

Answer 58

2-4L fluid/day

Question 59

What is the role of the lymphatic system?

Answer 59

drains excess interstitial fluid

Question 60

What can a blockage in lymphatic system lead to?

Answer 60

swelling

Question 61

How does lymph return to the CVS?

Answer 61

via subclavian veins - vein under the clavicle

Question 62

What are the other functions of the lymphatic system?

Answer 62

- transport of dietary lipids - lymph nodes/organs (immunology)