Lecture 1. Cardiovascular system Flashcards Preview

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Flashcards in Lecture 1. Cardiovascular system Deck (21):

Describe the composition of fluid in the body
ie/ what % is total body water, what % is intracellular fluid, extracellular fluid

Total body water = 60%; intracellular fluid = 40%; extracellular = 20%
ECF: blood plasma 4%, interstitial fluid 16%

blood volume = 4% of BW


Name the five functions of the CV system

transfer substrates and O2. to cells
transfer metabolites and CO2 from cells
hormone distribution
body defence mechanisms are carried in the CVS (eg/ antibodies)


how are substances moved between organs?

bulk transport


what is transport rate?

flow rate x concentration


what is velocity?

total flow / total cross sectional area


list x4 factors influencing diffusion rate

1. concentration difference
2. surface area
3. diffusion distance
4. permeability to that substance


form = function, describe how capillaries optimise diffusion of metabolites

capillary network = extensive (less that than 1cm away from every cell in body - metabolites don't have to travel far)
capillary barrier = 1 endothelial layer thin


what is vascular resistance?

force required to move a given volume of fluid through a system of blood vessels in a specific period of time


what is the flow equation?

Q = DP/R
DP = pressure difference (delta P)


what are the determinants of resistance?

poiseuilles law: R = (8 x viscosity x length) / (pi x internal radius)

resistance proportional to viscosity and length, inversely related to internal radius eg/
thicker liquid or longer tube = more resistance
bigger radius = smaller resistance


what are the determinants to blood flow

VISCOSITY (although this rarely changes)


different types and sizes of vessels are arranged sequentially, describe the requirements of blood flow with vessels in a SERIES
Rs = R1 + R2 + R3 ... etc

1. in a closed system blood flow must be equal in each segment preventing the build up of fluid
2. pressure drop will increase along the segments
3. the segment with the largest change in pressure will have the greatest resistance.


vascular beds within organs are often arranged in parallel, describe the requirements of blood flow with vessels in PARALLEL

resistance is given by ohm's law = 1/Rp = 1/ R1 + 1/R2 ... etc
total flow = DP/Rp
= overall resistance of system is lower than in any one compartment therefore blood flow to one organ can be altered without altering blood flow to other organs.


what are the four forces determining transcapillary fluid movement (bulk flow)

1. capillary blood pressure
2. plasma colloid osmotic pressure
3. interstitial fluid hydrostatic pressure
4. interstitial fluid colloid pressure


describe the net movement of fluid across a capillary

(Pc + πif) - (πP + Pif)
net pressure higher at arteriole end = filtration
net pressure lower at venous end = reabsorption


what is the role of the lymphatics?

not all blood reabsorbed at the venous end --> lymphatics responsible for returning excess interstitial fluid into venous circulation eg/ fluid and protein
- lymphatics dont have pressure gradient element generated by the heart and can therefore be affected by gravity


list the 5 components of the CV system

heart - needed to generate pressure
arterials - distribution
microcirculation - region of exchange
venous system - blood reservoir
lymph vascular - return excess lymphatic


x4 heart chambers = x4 valves, what are they?

x2 atrioventricular valves (mitral and tricuspid)
x1 pulmonic semilunar valve
x1 aortic semilunar valve


what is the dual circulation of blood?

left = oxygenated blood to system circulation
right = de-oxygenated blood to pulmonary


name the 3 components responsible for effective functioning of the heart?

1. conductivity
2. contractility
3. autorhymicity


describe the 5 components of effective cardiac pumping

1. regular and synchronised contractions
2. fully open valves - flow forward
3. no valve leaks - no flow backwards
4. adequate force of muscle contractions
5. adequate filling of ventricles