the

Blood Pressure in arteries is higher than in veins

blood pressure drops as blood gets

farther from the heart

the heart is a pump and so it does a

pump and then the blood has to go from

the heart all the way around the

circulatory system and back to the heart

again with the amount of pressure that

was pumped right here so pressure is

going to be highest at the moment of the

pump in the aorta and then pressure is

going to be very very lowest at the vena

cava so you can see that in our diagram

in our diagram on the y-axis we have

pressure in millimeters of mercury and

120 is typically the pressure that is

needed for the heart to be able to

successfully pump the blood all the way

around and then this bottom number 80 is

the pressure that is held in the pump or

in the ventricles of the heart even in

between heartbeats so use a red pen and

can write a Horta here obviously this is

going to be the highest pressure in the

body as far as blood pressure goes and

then it's going to start dropping so the

next I'm gonna actually turn the paper

sideways might be a little bit weird

that's not so bad you can see that right

so the large distributing arteries

those would be like the brachiocephalic

and the renal artery etc you can see

that pressure is dropping off a little

bit you still have a what's called a

pulse pressure that you could feel on

those arteries and then we get to the

arterioles here in that word holes at

the end this means little arteries and

the pulse pressure this little squiggly

line disappears by the end of the

arterioles

so by the time you get to the tiny

capillaries pressure has gone way down

and there is no pulse pressure so that's

good because that means blood flow is

always steady through the capillaries

then the capillaries drop off the oxygen

and other goodies at the tissue they

collect the waste product moist products

into veins you can use a blue pen there

and then last but not least the very

biggest vein in the body the vena cava

is going to have the lowest pressure and

in fact I'm gonna turn the paper again

if you look at what the pressure might

be in the vena cava it is so low we're

talking somewhere around three

millimeters of mercury and the

arterioles they typically start you

can't really I guess my picture is not

real great on that but the capillaries

are usually going to be about thirty

five millimeters of mercury and maybe

about fifteen by the time you get to the

end of the capillaries the arterioles

are going to be somewhere around 50

millimeters of mercury

and so we just see the steady drop as we

go through the blood system the

arterioles have the greatest impact on

blood pressure when they constrict

so when we talk about vasoconstriction

and vasodilation we're talking at the

arterial level allowing blood flow to go

to an organ or not and then another so

oh I wanted to say one more thing before

we end this page so if you are going to

be asked a question where is blood

pressure highest in the capillary or of

the vena cava you would say capillary

people tend to think oh a smaller blood

vessel lower blood pressure no that's

actually not the case it's the distance

from the heart so the aorta is the very

closest to the heart it has this great

high blood pressure and then it by the

time you get to the capillaries blood

pressure has gone down from let's say

120 to somewhere around I don't know 30

as it passes through you can see it's

dropping continually and then it

continues to drop so that you barely

have enough pressure to get the blood to

drop back in to the heart by the time

you've come all the way around you're as

far away from the heart as you'll get

and then coming back to it let's use a

green highlighter to highlight the pulse

pressure

oops sorry you couldn't see that so the

pulse pressure is the difference pulse

pressure difference between systolic and

diastolic values