IMAT Biology Lesson 6.4 | Anatomy and Physiology | Circulatory System I

Summary

In this anatomy and physiology video, Andy from Med School EU delves into the circulatory system, focusing on blood vessels and circulation. He explains the journey of blood from the right ventricle through the pulmonary artery to the lungs, then to the left atrium and ventricle, and finally to the body via the aorta. The video also covers the structure of arteries and veins, highlighting the differences in thickness and function, and touches on blood composition, distinguishing between plasma, red and white blood cells, and platelets.

Takeaways

• 😀 The video script is part of a series on anatomy and physiology, focusing on the circulatory system.
• 🔍 The script is divided into two parts: one on blood vessels and blood circulation, and another on the heart.
• 💓 The circulatory system is introduced with an explanation of how blood is pumped by the heart and circulates throughout the body.
• 📍 The right ventricle is identified as the starting point of the blood circulation process in the diagram provided.
• 🔵 The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs for oxygenation.
• 🔴 The left atrium receives oxygenated blood from the lungs via the pulmonary veins.
• 🚀 The left ventricle pumps oxygenated blood into the aorta, which then distributes it throughout the body.
• 🔄 The superior and inferior vena cava return deoxygenated blood from the upper and lower body back to the right atrium.
• 🌌 Blood vessels are categorized into arteries, veins, and capillaries, with distinct structures and functions.
• 💪 Arteries have thick walls with smooth muscle and elastic fibers to withstand high blood pressure from the heart.
• 🔄 Veins have thinner walls and contain valves to prevent backflow, ensuring blood returns to the heart efficiently.

Q & A

What is the primary focus of the first video in the anatomy and physiology unit?

The first video in the anatomy and physiology unit primarily focuses on the blood vessels, the circulation of blood, and the blood contents.

What are the two main parts of the heart that pump blood?

The two main parts of the heart that pump blood are the ventricles and the atria.

Where does the blood pumped from the right ventricle go?

The blood pumped from the right ventricle goes into the pulmonary artery.

Why is the pulmonary artery considered an artery despite carrying deoxygenated blood?

The pulmonary artery is considered an artery because it is a blood vessel that leaves the heart, regardless of whether the blood is oxygenated or deoxygenated.

What happens to the blood in the lungs?

In the lungs, the deoxygenated blood gets oxygenated as carbon dioxide leaves the body and oxygen enters the circulatory system.

What is the role of the left atrium in the circulatory system?

The left atrium receives oxygenated blood from the pulmonary veins and then pushes it down to the left ventricle.

What is the function of the aorta in the circulatory system?

The aorta is a major artery that carries oxygenated blood from the left ventricle to the rest of the body.

How do veins differ from arteries in terms of structure?

Veins have thinner walls compared to arteries, which have more smooth muscle and elastic fibers, making arteries more flexible and able to sustain higher blood pressure.

What is the purpose of the valves in veins?

The valves in veins prevent the backflow of blood, ensuring that blood flows in one direction towards the heart.

What is the main function of blood plasma in the blood?

Blood plasma makes up the majority of the blood and serves as a filler, providing blood volume to prevent shock and playing a role in blood clotting.

What are the formed elements in the blood and what do they include?

The formed elements in the blood make up about 45% of the blood and include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).

Outlines

00:00

💓 Introduction to the Circulatory System

In this introductory segment, Andy from Med School EU begins a detailed exploration of the circulatory system, focusing on the blood vessels and the circulation of blood. The video is planned to be split into two parts, with this one detailing the blood vessels and the next focusing on the heart. The discussion starts with the right ventricle, the lower chamber of the heart responsible for pumping blood, and moves through the pulmonary artery to the lungs, where deoxygenated blood is oxygenated. The left atrium receives this oxygenated blood from the pulmonary veins, and the left ventricle pumps it out to the rest of the body through the aorta. The explanation emphasizes the distinction between arteries and veins and clarifies that the pulmonary artery carries deoxygenated blood, contrary to a common misconception.

05:01

🔍 Anatomy of Blood Vessels

This paragraph delves into the anatomy of blood vessels, highlighting the structural similarities and differences between arteries and veins. The outer layer of both types of vessels is made of connective tissue, while the middle layer, known as the tunica media, consists of smooth muscle and elastic fibers. Arteries are distinguished by their thicker walls, which contain more smooth muscle and elastic fibers, allowing them to withstand higher blood pressure. Veins, on the other hand, are thinner and have less muscle and elastic tissue. The innermost layer, the endothelium, is common to all blood vessels and is characterized by its smoothness, which reduces friction and prevents blood clotting. Additionally, veins are noted for their one-way valves that prevent backflow of blood, a feature crucial for maintaining circulation against gravity.

10:02

🏃‍♂️ Functioning of Veins and Arteries

This section discusses the unique functions of veins and arteries, particularly the role of veins in preventing blood backflow. Veins, equipped with one-way valves, ensure that blood flows in a single direction, crucial for maintaining circulation in the legs, especially during prolonged standing or exercise. The importance of muscle activity in aiding venous return is emphasized, as muscle contractions push blood upwards against gravity. Arteries are highlighted for their high blood flow and pressure, with the aorta being the primary artery that branches into smaller arteries, arterioles, and eventually capillaries. The discussion also touches on the role of arterioles in controlling blood flow by constricting or dilating, thus regulating the distribution of blood to different parts of the body.

15:04

🌡️ Regulation of Blood Flow

This paragraph focuses on the regulation of blood flow through the circulatory system, emphasizing the role of arterioles. Arterial blood pressure is high due to the direct connection to the heart, and arterioles, with their smooth muscle, help slow down the blood flow before it enters the capillaries. This regulation is crucial for ensuring that blood reaches the capillaries at a slower pace, facilitating efficient gas exchange. The discussion also notes that capillaries are the only blood vessels composed solely of endothelium, being extremely fragile and one cell thick. Venules, which collect blood from capillaries, contain some fibrous tissue and merge into larger veins that return blood to the heart.

20:04

🩸 Blood Volume and Composition

In the final paragraph, the focus shifts to the volume and composition of blood. Blood volume is noted to be approximately 5 to 6 liters for males and 4 to 5 liters for females, making up about 6 to 8 percent of total body mass. Blood plasma, which is non-cellular, constitutes about 55 percent of the blood and serves as a filler, providing volume and playing a role in blood clotting. The remaining 45 percent, known as formed elements, includes platelets (thrombocytes), white blood cells (leukocytes), and red blood cells (erythrocytes). Red blood cells make up 99 percent of the formed elements and are crucial for oxygen transport. The buffy coat, a thin layer of platelets and white blood cells, is also mentioned, highlighting its role in blood clotting.

Keywords

💡Circulatory System

The circulatory system is the body's 'transport' network, responsible for circulating blood throughout the body. It includes the heart, blood vessels, and blood itself. In the video, the circulatory system is the central theme, with a focus on how blood is pumped and circulated by the heart to supply oxygen and nutrients to the body's cells and remove waste products.

💡Blood Vessels

Blood vessels are the conduits of the circulatory system, including arteries, veins, and capillaries, which transport blood to and from the heart. The script discusses the structure and function of different types of blood vessels, emphasizing their roles in the circulation of blood, such as the pulmonary artery carrying deoxygenated blood to the lungs.

💡Heart

The heart is a muscular organ that serves as the central pump of the circulatory system. It is composed of chambers (ventricles and atria) that contract to push blood through the blood vessels. The script mentions the right and left ventricles and their role in pumping blood to the lungs and throughout the body, respectively.

💡Right Ventricle

The right ventricle is the lower chamber of the heart that pumps deoxygenated blood into the pulmonary artery, which leads to the lungs. In the script, the right ventricle is identified as the starting point of the circulatory pathway, highlighting its role in sending blood rich in carbon dioxide to be oxygenated.

💡Pulmonary Artery

The pulmonary artery is an artery that carries deoxygenated blood from the right ventricle to the lungs for oxygenation. The script clarifies a common misconception that all arteries carry oxygenated blood, noting that the pulmonary artery is an exception as it transports deoxygenated blood.

💡Left Atrium

The left atrium is the upper chamber of the heart that receives oxygenated blood from the lungs via the pulmonary veins. The script describes the left atrium as the recipient of blood that has been oxygenated in the lungs, preparing it to be pumped to the rest of the body.

💡Aorta

The aorta is the main and largest artery in the body, originating from the left ventricle and branching into smaller arteries, arterioles, and capillaries. The script explains that the aorta is responsible for distributing oxygenated blood to the entire body, excluding the lungs.

💡Vena Cava

The vena cava are the two largest veins in the body, with the superior vena cava and inferior vena cava carrying deoxygenated blood from the upper and lower body, respectively, back to the right atrium of the heart. The script identifies these veins as the major pathways for returning blood to the heart to restart the circulatory cycle.

💡Blood Plasma

Blood plasma is the liquid component of blood, making up about 55% of its volume. It is a yellowish, non-cellular fluid that serves as a transport medium for cells, nutrients, and waste products. The script mentions blood plasma as a crucial part of blood composition, highlighting its role in blood volume and clotting.

💡Formed Elements

Formed elements are the cellular components of blood, including red blood cells, white blood cells, and platelets, making up about 45% of blood volume. The script discusses the formed elements as essential for various functions such as oxygen transport (red blood cells), immune response (white blood cells), and clotting (platelets).

💡Endothelium

The endothelium is the innermost layer of blood vessels, made up of specialized connective tissue that lines the entire vascular system. The script describes the endothelium as having a smooth surface to reduce friction and prevent blood clots, ensuring the smooth flow of blood.

💡Arterioles

Arterioles are small arteries that branch from larger arteries and regulate blood flow to capillaries by constricting or dilating. The script explains that arterioles play a critical role in controlling blood distribution to different parts of the body, adjusting to meet the body's needs.

Highlights

Introduction to the anatomy and physiology unit focusing on the circulatory system.

Explanation of the division of the circulatory system into two videos: blood vessels and heart anatomy.

Overview of the blood circulation process pumped by two parts of the heart.

Description of the right ventricle's role in pumping deoxygenated blood into the pulmonary artery.

Clarification that arteries leaving the heart carry deoxygenated blood in the case of the pulmonary artery.

Details on how the pulmonary artery transports blood to the lungs for oxygenation.

Explanation of the left atrium's function in receiving oxygenated blood from the pulmonary veins.

Description of the left ventricle's role in pumping oxygenated blood to the body through the aorta.

Importance of the aorta in distributing oxygenated blood to the body's organs and tissues.

Discussion on the return of deoxygenated blood to the heart via the vena cavas.

Anatomy of blood vessels, distinguishing arteries and veins based on their structure and function.

Comparison of the tunica media layer in arteries and veins, highlighting the difference in thickness and composition.

Role of the endothelium in providing a smooth surface for blood flow and preventing clots.

Function of valves in veins to prevent backflow and facilitate upward blood flow against gravity.

Importance of muscle contractions in aiding the return of blood from the veins to the heart.

Composition of blood, distinguishing between blood plasma and formed elements.

Blood plasma's role as a major component providing volume and参与 in blood clotting.

Breakdown of formed elements into red blood cells, white blood cells, and platelets, with their respective functions.

Conclusion of the lecture with a preview of the next video focusing on the heart's functions and anatomy.

Transcripts

[Music]

hello everybody this is andy from med

school eu

today we are going to continue on with

the anatomy and the physiology unit and

we are going to start off with

the circulatory system so i'm going to

break this down into two separate videos

this video will be primarily focused on

the blood vessels and the circulation of

the blood and the blood contents

and the next video will be specif

specifically focused

on information about the heart

so let's begin with a brief overview of

the circulatory system

we're going to see how

the blood circulates all around the body

and how it is pumped

by two parts of the heart

so we're going to begin with the

numbering here we're going to start off

with the right ventricle so the bottom

part of the heart this this big one

right here is the ventricle

and the ones that are at the top there's

two parts the top those are the atrium

so the ventricles are going to be

the chambers that pump the heart

and they pump the blood out of the heart

and it distributes throughout the body

so we're going to begin here with number

one and this part is is called the right

ventricle so i'm just going to label it

as as r

for right

ventricle

and this is this is a circulatory system

so it's it completes a full circle we

can begin anywhere

but um according to this diagram we're

going to begin with the number one here

so as you can see the blood is going to

be

the the heart is going to contract and

the blood is going to be pumped out of

the right ventricle

and it's going to go right into the

pulmonary artery so any blood vessel

that leaves the heart doesn't matter if

it's oxygenated or if it's deoxygenated

it is going to be an artery

anytime it leaves

the heart it's an artery any time it

arrives at the heart it's a vein

so in this case we're going to have

the right ventricle pumping over to

number two and that's the pulmonary

artery

why it's pulmonary because

it is going to pump the blood

deoxygenated blood as you can see blue

here is the deoxygenated blood doesn't

have oxygen has

plenty of carbon dioxide

now this this blood is going to be

pumped over to

the right and the left pulmonary artery

each is going to reach the right and the

left

lung so that's where the deoxygenated

blood goes

from the right ventricle a lot of the

times students make the mistake that if

it's an artery it must have oxygenated

blood however that's not the case for

the pulmonary artery because this one

pumps

deoxygenated blood to the lungs where

it's going to get oxygenated as you can

see the capillaries here

so these are all capillaries

capillaries they're going to be they're

going to get oxygenated so the carbon

dioxide is going to leave

our body and oxygen is going to enter

the circulatory system and the now the

blood is going to be carried over to

number four here

and number four

is going to be the left atria

so left

atrium

atria is the pleural atrium is the

singular

so the left atrium is now going to

receive

blood from the pulmonary vein

pull

monary

veins

it's a vein because it arrives at the

heart

even though it's oxygenated it's still a

vein

and it's going to arrive at the left

atrium

now well of of course that's the right

pulmonary vein here we got the

left pulmonary vein

it arrives both of them arrive at number

four here left atrium now from the left

atrium the heart is going to contract at

the top so there's going to be a

stimulus at the top in the atria and

it's going to push the blood down to

the left ventricle

ventricle

now at number five from the left

ventricle

the

blood is this is now oxygenated blood is

gonna be pumped out to the rest of the

body is going to be distributed all over

the body now it passes this very

important artery it's called the aorta

so we'll label it here a

aorta

and aorta is going to break off into

of course smaller arteries then it's

going to break off into arterioles and

then it's going to break off into the

capillaries so this is the

lower body

lower body is now going to get the

oxygen it needs and this is the upper

body

excluding the lungs

so now

the rest of the body gets oxygenated

blood for the cells where they receive

the oxygen they're going to offload

their carbon dioxide and it's going to

travel back

through the vena cavas the two major

veins

that where the

deoxygenated blood arrives at

the right atrium of the heart

are called vena cavas so the one that's

above here number nine is going to be

superior

superior

vena cava i'm just going to label this

as vc

and the one at number 10 the one that's

coming from the lower body is going to

be the inferior vena cava so

inferior

vena cava so of course there's going to

be all these little

veins first and or venules then into

bigger veins and it ends up in one of

the biggest

veins that are it called vena cavas from

the top it's going to be superior from

the bottom it's inferior vena cavas and

finally they're going to arrive at 11

and that's the right atrium and then the

whole cycle

begins all over again

next we're going to discuss the blood

vessel anatomy

so we're going to talk about the major

arteries first

and we're going to label some of these

structures and they're going to be very

similar to veins except for

a couple of small differences so this is

just gonna be like a cross section of uh

so this would be the artery

this this would be the general depiction

of all arteries aorta pulmonary artery

and so on and this would be a general

depiction of veins

so now we are going to begin from the

outside

and work our way inside so the

structures are

pretty much identical in terms of what

they are from artery to vein except

their thickness

is going to differ so the outside part

right here

the outside

is going to be called connective tissue

this is connective

connective tissue and and we had a brief

introduction about connective tissue

in our previous lectures

now looking at the inner more inner

structure the one that's in the middle

here it's called tunica media

in in latin however this is made up of

smooth muscles and

elastic fibers

so let's make labels for that as well

these ones right here so this this is

made up of smooth muscle

so the important thing to notice here is

that arteries

have gigantic smooth muscle and elastic

fibers compared to the veins so the

veins still have smooth muscle and

elastic fibers in in one of these layers

however this the thickness of the artery

is is almost three times more

simply due to

having more volume of the smooth muscles

and the elastic fibers meaning that the

artery is more flexible it's able to

sustain higher blood pressure and it

only makes sense because arteries come

right off from the heart where the blood

pressure is at its peak so the aorta has

to sustain

very strong blood pressure before it

slows down to the veins because

blood pressure in the veins is going to

be

quite low it could get high if there is

lots of blood buildup in

for example in the legs if you're

standing for a long time the veins in

the legs are going to have

in the inferior vena cava is going to

build up quite a lot

however there is a mechanism to push the

blood along and the blood flow in the

artery is going to be much much higher

than in the veins because artery comes

right off the heart whereas veins kind

of slowly drain into

the heart to get the blood

back in there

and let's label the final layer the one

that's on the

the innermost layer here

and this one is going to be called

endothelium

endo see

liam an endothelium exists in all types

of

blood vessels so this would include

capillaries it would include venules it

would include arterials the inner layer

of every single blood vessel in our body

is made up of endothelium and

endothelium is simply connective tissue

that we discussed here

however it is specialized connective

tissue in a sense that it makes the

surface extremely smooth

so it's very smooth surface to reduce

friction because you don't want

blood clots you don't want

anything attaching to the surface of the

the blood vessels so you do not get any

blood clots and the red blood cells and

other substances in the blood can flow

smoothly

now if the endothelium is damaged if the

endothelium gets

gets

rough in its inner surface

it's going to have a great impact and

it's going to increase the likelihood of

many diseases now another thing that is

very

unique to

veins compared to other

blood vessels is that they have these

valves these one-way

one-way

valves

and the purpose of one one-way valves is

to prevent backflow of the blood so if

you could imagine that there is

a very low blood pressure very low

blood flow going through your legs

however somehow the blood is supposed to

make it from all the way from your toes

and your ankles

all the way up to the heart so it could

circulate again now how is that going to

happen how how are we going to achieve

this without having any backup

or or backflow because

if you are standing upright for 8 hours

you don't want to be getting any blood

clots or or any back flow in the veins

the way to prevent that is to have

one-way valves where the blood is going

to flow in one way so it's going to flow

this way here

and

it's

the valves are going to be shut for the

blood if it if it's if it wants to

return now one way to have

the blood pushed over faster and this is

why it's encouraged that people do some

walking or do some exercising or even

when you run imagine somebody's running

a marathon for four hours

and how does the blood make make their

way all the way up to their veins if

you're constantly pumping the blood down

to your legs

or how is the blood going to make it all

the way up to the heart from the veins

when

all the blood is going and pulling down

in the legs well the the reason why we

don't have

blood pooling in a healthy individual is

because we have muscles that push

the blood upwards so the veins are

situated in places where there are

muscles that are in constant work so if

you have a vein going like this

and you have

muscle belly right there and muscle

belly here now imagine you're going to

be walking now these muscles are going

to be activating they're going to be

contracting each time they contract it's

going to push the blood flow up because

if it pushes

but it cannot go backwards it can only

go one way because of these one-way

valves so here we're gonna label some of

the structures that are associated with

each type of blood vessel so we got

artery we talked about artery and vein

so as you can see here it's pretty much

a similar depiction

is that the elastic fibers of the

arteries so these blue ones this is

elastic fibers

the elastic fibers are much thicker and

the artery contains a lot more smooth

muscle so this is i'm going to label

this as sm smooth muscle right here as

you can see the artery has the most

smooth muscle compared to any other

blood vessel now another thing to note

is that

uh the this is this is going to be the

endothelium

i'm just going to label this as endo

right here

and the endothelium exists that's the

most inner part it exists in all types

of blood vessels in equal proportions so

in arterials in capillaries and venules

they exist in the same proportion as the

arteries in the vein

now another thing to note here is that

the arterioles which are

basically designed to slow down blood

flow before it enters capillaries

because arterioles have smooth muscle

and the smooth muscle is going to

contract and relax when

it needs to dilate or constrict so the

arterioles are going to control

blood flow to certain parts

of the body for example

if

you have a drop in blood flow or a drop

in

cardiac output meaning that

your heart

is not pumping out as much blood as it

should

for example when you're sleeping the

cardiac output is typically reduced at

that point the arterioles the smooth

muscle in the arterials is going to

relax

so it's going to

dilate and when it dilates they get

bigger which increases blood flow

it reduces the resistance and it

increases blood flow so for example in

parts of the body like the brain

and other vital organs you have to

sustain

blood pressure and blood volume

the same so

even when you're when you're exercising

or when you're sleeping

your brain is going to receive the same

amount of blood

no matter what activity you're doing

because if it doesn't

then

you're typically going to faint if it

receives less and it also cannot receive

more as that

it increases more problems

so the important thing to note here is

the arterioles are responsible for

slowing down the blood from the arteries

because arteries are going to have crazy

pressure remember the

arteries come right out of the heart and

they're going to sustain crazy amount of

blood pressure so they're going to have

lots of blood flowing at very high speed

now you cannot even have gas exchange

when the blood is just zipping by so you

need another structure which is the

arterial that are just smaller arteries

that

do not have the

as much elastic fibers or don't have any

elastic fibers and they also don't have

much fibrous tissue so this is

fibrous tissue

however they have these smooth muscle

that is responsible for slowing down

blood pressure from the artery so that

it can then reach the capillary at very

slow pace and then gas exchange

could occur

now note that the capillary is

the only blood vessel

that

only has

endothelium because the venules that

come off right from the capillaries

these venules also have some fibrous

tissue around however the capillaries

are very fragile as they're

one cell thick

making up the endothelium

and of course

venules then quickly

transform and combine into larger veins

that are then going to carry the blood

over and and back to the heart so now we

are going to discuss blood volume and

blood content so first let's begin with

with blood volume

and take a look

at how much blood we have in our bodies

so for males

we'll start off with males here

we have five to six

liters of blood depending on the male

size of course now females on average

are going to have four to five liters of

blood so just a liter less

and

blood typically makes up about six to

eight percent

of the total

body mass so the entire mass of the body

just the six to eight percent makes up

volume of the blood

and

it makes up about 20 percent of the

extra cellular

fluid

so the fluid that is around the cells it

makes up about 20 of that

and we are going to discuss this

specific statistic in greater detail

when we talk about the

immune system

so now let's discuss the composition of

the blood

so here

we'll discuss composition

and

and the content of the blood

so first this this yellow part

we have something called blood plasma

so this is the blood

plasma

and blood plasma makes up

the majority of the blood which is going

to be about 55

of the blood as you can see here this

has more than than the red part

and blood plasma is is this yellowish

structure it's non-cellular so it

doesn't contain any cells but the major

function of the blood plasma is

basically

just a filler so

it it provides the patient with blood

volume which can prevent shock and it

also has plays a factor in blood

clotting

now looking at the other elements

that make up about 45 percent of the

blood which is going to be the rest that

is not part of blood plasma

these are called formed elements

this is formed

elements

which is 45

of the blood and that's going to include

this white layer and the red part now

this this white layer is called the

buffy coat so i'm going to label it here

it's going to be called

buffy coat

puffy coat

because it's kind of if you spin the

blood in the centrifuge this is kind of

what you get you get this buffy coat

and

it's basically made up of platelets

which are responsible for blood clotting

platelet plate

let's

and

they've they're part of the white blood

cells and they make up a very small

amount i would say about one percent

of the formed elements now the rest the

44 of the formed elements

make up red blood cells

so the red blood cells are the the red

part right here

and

platelets are also called thrombocytes

and white blood cells are called

leukocytes so leuco

glucosites

and red blood cells are called

erythrocytes

very throw sites so sometimes when we're

gonna discuss

things about the red blood cells which

we will

i may refer to them as

erythrocytes and they

make up 99

of the formed elements and that's this

part right here so that's the general

depiction of of the composition

of the blood so this concludes our first

lecture on the circulatory unit from the

anatomy and the physiology of humans in

the next video we're going to finish off

this circulatory unit with

functions and anatomy of the heart

[Music]

you