Introduction to the cardiovascular system, the physics of blood flow

label this 

what is the basic direction of flow of blood in the heart

1. Deoxygenated blood enters the heart via:

   • Superior vena cava (from upper body)

   • Inferior vena cava (from lower body)
     ↓

2. Right atrium
   ↓

3. Through the tricuspid valve (right AV valve)
   ↓

4. Right ventricle
   ↓

5. Through the pulmonary valve (pulmonic semilunar valve)
   ↓

6. Into the pulmonary artery
   ↓

7. To the lungs → gas exchange (becomes oxygenated)
   ↓

8. Pulmonary veins
   ↓

9. Left atrium
   ↓

10. Through the mitral valve (bicuspid / left AV valve)
    ↓

11. Left ventricle
    ↓

12. Through the aortic valve (aortic semilunar valve)
    ↓

13. Aorta → oxygenated blood pumped to the body

what happens during atrial systole

• contract/relax

• valves 

• flow 

• pressure

• atria contracts 

• tricuspid and mitral valve open 

• pulmonary and aortic valve closed to stop backflow from arteries to ventricles 

• blood flows from atria to ventricles

• pressure rises slightly in atrium and ventricle 

why is the right side of the heart thinner than left

left has thicker muscles as needs to pump blood all around 
right just needs to pump to the lungs

describe what happens in the blood pressure as it moves from arteries to arterioles to capillaries to veins

Blood pressure decreases steadily:

• High in arteries

• Falls sharply in arterioles (main resistance site)

• Low and steady in capillaries

• Very low in veins

describe the pressure change in the left ventricle

• low during diastole

• high during systole

what is the flow into the heart known as
 and what is it normaly 

venos return 
5L/mil

what is venos return equal to 

CO ( cardiac output )

what is stoke volume

volume of blood pumped out by the heart per beat

what is cardiac output

volume of blood flow out of the heart per minute
5L/min

how to calculate cardiac output

cardiac output = stroke volum x heart rate

mean arterial pressure/  total peripheral resistance

what is total peripheral resistanc ( TPR )

the total resistance of all the blood vessels in the systemic circulation 

what is afterload

the pressure the ventricle must overcome to eject bloood during systole

how to calculate flow

change in pressure / change in resistance

what is preload

the filling pressure of the heart

what is preload determined by

central venous pressure - pressure in vena cava

what is systolic pressure

the max pressure reached

what is diastolic pressure

the lowest pressure reached

what is pulse presure

the differnce between systolic and diastolic pressure

how to calculagte mean arterial pressure (MAP)

diastolic pressure + ( systolic pressure-diastolic pressure)/3

just to visualise

what is the advantage of the aorta having elastic wall and there being large arteries during the cardiac cycle?

They can stretch and store some energy and this stored energy maintains blood flow during diastole

what structual features  determin resistance ot flow and to what extent

length of tube - the longer the more resistance ( only slight change) 
viscocity of fuid -  the thicker the more resistance
radius of tube - the wider the less resistance ( biggest effect, small change in radius makes lareg change in resistance as R⁴

Why is it important to always measure BP at the level of the heart?

because gravity has a direct effect on BP due to the weight of column of blood .

what does darceys law say and what calculation comes with it 

flow is proportional to the pressure differnce ( p1-p2) and inversly propertional to the resistance of flow (1/R)

flow= (p1-p2)/R

what is poiseuille law ( resistance of flow ) 

R = 8VL/πr^4

what is laminar flow

• blood flows unidirectionally 

• there is viscous drag at the side of the tubes that slwo down the fluid so the fastest movement is in the centre

what is axial streaming

the cells flowing in tubes become aligned in the fastest section of the moving fluid

what are the diameters of red blood cells and capillaries

capillaries- 6 micro meteres 
RBC- 7 micro meteres

what is disturbed flow and how does it ocur

• when there is turbulance in the blood and it doesnt flow unidirectionally 

• cuased by: sharp edges, high velocity, branch points

how are mumurs caused in the blood flow

tubulent blood flow makes mumurs as the blood hits the walls of the vessels

what happens durign ABCDEFG

A - atrial systole (mitral & tricuspid valves open)
B - isovolumetric contraction (mitral & tricuspid valves shut)
C - rapid ejection (mitral & tricuspid valves shut)
D - reduced ejection (mitral & tricuspid valves shut)
E - isovolumetric relaxation (mitral & tricuspid valves shut)
F - rapid ventricular filling (mitral & tricuspid valves open)
G - slower ventricular filling (mitral & tricuspid valves open)

what happens at the Left atrium pressures at  ACV

label diastolic volume, systolic volum and stoke volume

what happnes during diastole 

• relax/contract 

• valve open/closed

• blood flow?

• pressure 

• heart relax

• aortic and pulmonary valve closed 

• mitral and tricusbid valve open 

• nlood enters from vena cava and pulmonary veininto pulmonary artery and as the AV valves are open also the ventricle 

• pressure is the same in the atria and ventricle as the AV valves are open 

what happens durign ventricular systole 

• relax/contract 

• valve open/closed

• blood flow 

• pressure

• ventricle contracts 

• mitral and tricusbid valve closed- to stop backflow 

• aortic and pulmonary valve opens

• ventricula pressure rises when it becomes higher than pressure in aorta and pulmonary artery the semilunar valves open 

• blood flows out

describe the differnce in resistance and pressure in the pulmonary vs systemic circulation

pulmonary:

• low resistance

• low pressure

• right ventricle-lungs-left atrium so short distance

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systemic:

• high resistance

• high pressure

• left ventricle- body-right atrium

• needs to travel far