overview of cardiovascular system Flashcards
Function of CVS (3)
Transport respiratory gases, nutrients and waste
Signalling system - distributes hormones, inflammation molecules etc to target issues
Temperature regulation through
cutaneous heat conservation / dissipation
diffusion - distance related to time relationship
t proportional to x2
Time t needed to diffuse a net distance x is proportional to the square of distance
how does cvs provide fast and directional transport?
convection (movement by pressure gradient)
how does the heart achieve fast and directional transport?
Output of blood at high pressure
Creates a pressure difference with distance blood vessels
Aorta (>100mmHg), Large veins (5-10 mmHg)
Pressure difference drives blood flow
what is cardiac output?
equation?
volume of blood ejected from ventricles per minute
heart rate x stroke volume
what has highest cardiac output in the body?
liver + gi = 25%
what organs are relatively under-perfused?
coronary and brain
clinical importance of under perfusion?
clinical problems e.g. angina, MI, stroke triggered by a relatively moderate fall in perfusion
Need to carefully control cardiac output
what controls cardiac output? (3)
1) Filling pressure (starling’s Law - in to out)
2) sympathetic/parasympathetic autonomic nerves controls CO by regulating HR and contractility (SV)
3) chemical factors - hromones (adrenaline)
how does the velocity of the blood change from aorta? And why? importance of this?
Velocity greatly reduces and is very slow at capillaries because then more time to exchange molecules.
veolicity decreases because CSA increases from 1 aorta to many arterioles and many more capillaries
why does velocity increase from capillaries to veins?
as the CSA decreases, velocity increases therefore blood has momentum to get blood back to heart
why is the increase in velocity in blood flow of veins important?
low pressure in veins so less drive to get blood back to heart so relies on kinetic energy
blood pressure equation
BP = CO x TPR
relationship between blood flow and blood pressure
blood flow equation
proportional to pressure across blood vessel
inversely proportional to resistance of blood vessel
Blood flow = (Pa - Pv) / Resistance
↑ Resistance = ↓ blood flow
what determines blood velocity?
equation?
Blood flow (cm3/s) / Cross-sectional area (cm2)
number x πr2 per vesselwhy does velocity decrease?
goes from Aorta, 1 large vessel with low cross-sectional area TO Capillaries made up of billions of small vessels with Huge cross-sectional area
why is slow velocity at capillaries important?
Velocity is much slower in capillaries allowing gaseous/nutrient exchange to occur
what is meant by dual system?
importance of this?
right blood flow goes to lungs and left goes to rest of the body at the same time
hence can oxygenate and remove co2 WHILST ejecting oxygenated blood via circulatory system
parallel blood supply
importance?
CO is split up hence safeguards the o2 supply in organs - most organs supplied this way
series blood supply
medical significance?
same blood supply between organs hence lower perfusion -> medical significance of under-perfusion in 1st organ
series blood supply examples
liver + kidney
liver series - why?
blood goes to spleen + intestine to pick up nutrients and then go to liver hence liver recieves de-oxygenated blood due to the exchange at before organs BUT liver recieves o2 from hepatic arteries
what part of kidney can be under perfused and why?
Tubules of kidney may recieve less o2 due to being in series once filtered
structure of artery and veins? (3)
Intima
Media
Adventitia
what is in adventitia layer? (3)
provides collagenous connective tissue for mechnanical support
has vasa vasorum -> small blood supply for wall of blood vessels
autominc nervous system innervation
media layer
what is in it and what does it do?
vascular smooth muscle cells + elastin
controls the size of the lumen
intima layer (3)
fenestrated elastic lamina
basal lamina
endothelial cell -> interaction between blood flow and blood vessel hence info via blood to contract or dilate
4 functional groups of blood vessels
elastic vessels, resistance vessels, capacitance vessels, exchange vessels
elastic vessels
what? role (2)?
large arteries, e.g. aorta
Accommodate stroke volume And Convert intermittent ejection into continuous flow
resistance vessels
what? role (2)?
(arterioles)
Control arterial BP
Control local blood flow
exchange vessels
what? role (3)?
(capillaries, only endothelium layer)
Nutrient delivery to cells
Tissue water & lymph formation
Removal of metabolic waste
capacticance vessels
what? role (2)?
(venules, veins)
Control filling pressure
Reservoir of blood
distribution of blood volume
10% - lungs 10% - heart 10% - arteries 5% - capillaries 65% - systemic veins and venules therefore serves as a reservoir
