the

Circulatory System| How The Heart Functions as a Double pump

hey it's Michelle your CSC biology tutor

in this video on the circulatory system

I'm going to be paying special attention

to hold the heart functions as a double

pump so we know that in heart is a

muscular organ and it's responsible for

pumping blood and throughout the entire

body so you need to understand that the

heart is divided into the left side and

the right side which is separated by a

septum so it consists of four chambers

we have the left atrium and the left

ventricle and then the right atrium and

the right ventricle so I mentioned that

the heart functions as a double pump so

that simply means that the blood is

going to enter the heart twice so you

will realize that I have the left and

the right sides color-coded using red

and blue so let's take a look at the

diagram of the heart so as you can see

the right-hand side highlighted in blue

that simply represents the deoxygenated

blood that will be passing through that

side will be heart the left-hand side

highlighted in red represents oxygenated

blood that would pass through that side

so you can clearly see the septum will

separate these two sides of the heart to

prevent the blood from mixing so you

don't want the blood on the left side

mincing with the blood on the right side

so that septum is important in

separating the different set two sides

of the heart so let's pay attention to

why the heart is really separated into

two sides and why we have oxygenated

blood coming

through the left hand side and then

deoxygenated both coming through the

right hand side so you're going to show

you the blood flow through the heart

twice okay so like we're going to start

on the left hand side of the heart but

you need to understand that the blood is

going to be entering each side

simultaneously so as in heart is pumping

the blood will be entering the left hand

side carrying the oxygenated blood and

then it's going to be entering the right

hand side carrying deoxygenated blood is

going to be all happening at the same

time but for explanatory purposes I'm

going to start with one side and explain

what happens blood as it enters

the heart twice so let's start from the

left hand side so blood rich in oxygen

is going to be coming from the lungs so

this is the oxygenated blood rich in

oxygen coming from the lungs so you

remember the lungs is responsible for

taking in oxygen and breathing out

carbon dioxide so that blood coming from

the lungs is going to be rich in oxygen

hence why it is called oxygenated blood

so it's going to enter the left hand

side of the heart through the pulmonary

veins so that word pulmonary means

related to the lungs so the pulmonary

veins collects the oxygenated blood from

the lungs and takes it to the left

atrium so that's the first chamber the

upper chamber usually smaller so that

left atrium is going to receive the

oxygenated blood and when the left

atrium contracts remember the heart is

made of muscular tissue cardiac muscle

so in order for it to pump that cardiac

muscle needs to contract so the left

atrium is going to contract and force

the oxygenated blood

into the left ventricle now you're going

to notice that we have a pair of valves

here bicuspid valve also known as the

mitral valve so that bicuspid valve

along with all the other valves in the

heart our B spot is responsible for

preventing back flow we want the blood

going in one direction only so you don't

want that blood going back where it came

from so as the left atrium contracts it

squeezes and forces that blood past li

bicuspid valve and into the left

ventricle

now the left ventricle once it receives

the blood from the left atrium that in

turn is going to contract and force the

blood up past the aortic valve so we've

seen another valve here so that a are

tight valve separates the left ventricle

from the aorta so that blood is going to

be pumped up into the aorta passing the

aortic valve and that oxygenated blood

needs to be transported and circulated

to all the organs of the body so the

aorta is the largest artery in the body

so it's going to be connected to various

organs it's going to be responsible for

transporting blood rich in oxygen to all

the various organs so that's what you

see these various branches as

representing arteries are going to be

connected to the different organs of the

body so that blood ratio and oxygen once

it has offloaded its oxygen and the

various nutrients that it will be

carrying to the tissues in the organs it

then needs to return to the right hand

side of the heart so by know that blood

is going to be lacking oxygen so that's

why we refer to it as deoxygenated blood

so is laughing oxygen so it needs to

return to the heart in order for it to

collect the oxygen again

and lungs so this deoxygenated blood is

going to enter the vena cava and you

realize you have two branches of the

vena cava we have the superior vena cava

which would be brain blood from the

upper body and then the inferior vena

cava which should be brain body brain

blood from the lower body so these two

branches of the vena cava is going to be

brain in the deoxygenated blood into the

right side of the heart so that

deoxygenated blood enters the right

atrium the upper chamber and then once

our right atrium contracts it's going to

force the blood past the tricuspid valve

so you see in another valve here so that

tricuspid valve

remember the valves are responsible for

preventing back flow so the blood passes

the tricuspid valve and is forced into

the right ventricle now the right

ventricle when that contracts that is

when a 4c blood passed the pulmonic

valve also known as the pulmonary valve

so that separates the likely right

ventricle from the pulmonary artery

so that deoxygenated blood is going to

be carried through the pulmonary artery

towards the lungs why is it going to the

lungs typical oxygen because it's

lacking oxygen at this point so when

this deoxygenated blood enters the right

hand side of the heart the sole purpose

is to reach the lungs where it can

collect oxygen again so know that we

know that you should have an

understanding of how the blood enters

the heart twice let's just quickly

review all that I've discussed already

so the structure of the heart so

remember it's divided into the left side

and the right side and that is separated

by a septum so the heart consists of the

four chambers the left atrium and the

left

Trickle then the right atrium and right

ventricle

so in order to help you to remember

which side has which type of blood you

can use this acronym Lord

lor D so left oxygenated right

deoxygenated so that will definitely

help you to better understand which side

is carrying which type of blood and

another note here so if you look back to

the diagram you will notice that the

left ventricle

is actually thicker than the right

ventricle the reason for this is that

the blood that is forcing through the

left atrium to the left ventricle on

that that left side is responsible for

carrying blood throughout the entire

body so when the blood reaches the left

ventricle it is going to be under very

high pressure so that highly pressured

blood is going to be forced through the

aorta and taken to all the various parts

of the body so the reason that the

muscular walls of the left ventricle are

much thicker than the right ventricle is

because it has to withstand that greater

force that greater pressure of the blood

which has to be pumped up through the

aorta and taken to all the various parts

of the body with the right ventricle is

thinner because it's not going that far

the blood is not going that far it's

just being taken to the lungs which is

nearby so it doesn't have to withstand

as high pressure as the left ventricle

all right so let's let's review the

blood vessels that are connected to the

heart so on the left hand side you need

to remember remember the left side

bringing oxygenated blood taking out

that oxygenated blood to the entire body

so we have the pulmonary vein which

would take oxygenated blood to the heart

so that's taking the oxygenated blood

towards the left

atrium and the aorta is responsible for

taking the oxygenated blood to all the

organs of the body so remember that the

aorta is the largest artery in the body

so on the right side now we have the

vena cava and we have two branches in

superior and the inferior vena cava

remember that the superior vena cava

brings deoxygenated blood from the upper

part of the body while the inferior vena

cava brings the blood from the lower

part of the body so the vena cava is the

largest vein in the body so that is

taking deoxygenated blood towards the

heart

now the pulmonary artery would be

responsible for taking deoxygenated

blood to the lungs to pick up the oxygen

again so those are the important that

vessels that you have to remember now in

terms of the heart valves remember that

valves will prevent backflow of blood so

they keep the blood flowing in one

direction so we have the

atrioventricular valves which are

between the atria and the ventricles so

these including bicuspid valve or the

mitral valve on the left side and the

tricuspid valve on your right side now

the other set of valves are known as the

semilunar valves and these are found

between the ventricles and the arteries

so the aortic valve that would be phone

between the left ventricle and the aorta

well the pulmonary or the pulmonic valve

will be found between the right

ventricle and the pulmonary artery so

now we've examined the structure of the

heart and its associated blood vessels

let's take a look at the two types of

blood circulation so remember the heart

acts as a double pump brain blood into

the heart twice so basically this means

there are two different journeys that

blood will take before and after enters

the heart so the first journey or Luca

is a pulmonary circulation

on this journey deoxygenated blood from

the right side of the heart needs to be

taken to the lungs to receive oxygen

then once the blood has collected the

oxygen from the lungs it enters the left

side of the heart before it can go on

its journey around the body so they said

before a pulmonary means related to the

lungs so pulmonary circulation describes

the journey that the blood would take

from the heart to the lungs to pick up

oxygen and then from the lung city heart

to deliver that oxygen

now the second journey is a systemic

circulation the blood that is rich in

oxygen which enters the left side of the

heart needs to be now circulated from

the heart to all the body the body's

tissues and organs so that is why the

word systemic is used because it means

that the entire body is affected so

oxygen and the nutrients present in the

blood can be delivered to the entire

body so these are the two types of blood

circulation pulmonary circulation and

the systemic circulation so I hope you

now have a better understanding of how

the heart functions as a double pump

bring blood into the heart twice