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
body defence mechanisms are carried in the CVS (eg/ antibodies)
how are substances moved between organs?
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
PRESSURE DIFFERENCE (M. A. P.)
TOTAL PERIPHERAL RESISTANCE
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?