IMAT Biology Lesson 6.12 | Anatomy and Physiology | Immune System Part I

Summary

In this educational video, Andre from Med School EU introduces the complex immune system, the body's final major organ system, highlighting its critical role in defending against infections. The video outlines the immune system's two main components: the innate and adaptive responses, with a focus on the functions of various immune cells like phagocytes, neutrophils, macrophages, and lymphocytes. It also touches on the importance of recognizing self from non-self to prevent autoimmune diseases, setting the stage for a deeper dive into the innate and adaptive immune responses in the next video.

Takeaways

• 🛡️ The immune system is the body's defense mechanism against diseases and infections, constantly functioning to protect us.
• 🔬 The immune system is complex and not fully understood, with many aspects still being studied and explored.
• 🔑 Glycoproteins on cell surfaces help the immune system differentiate between self and non-self, preventing autoimmune diseases.
• 🏥 The immune system is divided into two parts: the innate immune system, which responds immediately to infections, and the adaptive immune system, which provides a stronger and more specific response later on.
• 🚑 Innate immunity acts as the first responders in the immune response, similar to CPR or first aid, while adaptive immunity is like the hospital care that follows.
• 🌱 Hematopoietic stem cells are the starting point for the development of all immune system cells, splitting into lymphoid and myeloid cells.
• 👨‍🔬 Myeloid cells produce various types of cells including neutrophils, eosinophils, monocytes, mast cells, basophils, dendritic cells, and macrophages.
• 🦠 Phagocytes, such as neutrophils and macrophages, engulf and destroy pathogens through a process called phagocytosis.
• 🚨 Histamine released by infected cells signals the immune system of trouble, attracting neutrophils to the site of infection through chemotaxis.
• 🔄 Lymphocytes, including B cells and T cells, are part of the adaptive immune response and are produced in the bone marrow, with T cells maturing in the thymus.
• 🧬 The diversity of B and T cells allows them to bind to specific antigens, even those from pathogens never encountered before, showcasing the adaptability of the immune system.

Q & A

What is the primary function of the immune system?

The primary function of the immune system is to protect the body from diseases and infections, keeping us alive by constantly functioning and being alert.

What are the two main components of the immune system?

The two main components of the immune system are the innate immune system and the adaptive immune system.

How does the immune system distinguish between self and non-self?

The immune system distinguishes between self and non-self using glycoproteins on the surface of cells. Healthy cells have specific glycoproteins that signal to the immune cells that they are part of the body and not to be attacked.

What is the role of the innate immune system in the body's response to infection?

The innate immune system responds immediately to an infection, acting as the first line of defense by initiating the fighting process against pathogens.

What is the adaptive immune system's response compared to the innate immune system?

The adaptive immune system provides a stronger response that occurs later on if needed. It is activated by the innate immune system and creates memory cells to recognize and respond to attacks more effectively if they occur again.

What are the two main types of cells in the immune system?

The two main types of cells in the immune system are lymphoid cells and myeloid cells.

What is the main function of phagocytes in the immune system?

Phagocytes are cells that perform phagocytosis, which means they engulf and dissolve pathogens and dead cells, playing a crucial role in the body's defense against infections.

What is the difference between neutrophils and macrophages in terms of their role in the immune response?

Neutrophils are short-lived cells that rapidly attack pathogens, while macrophages have a longer lifespan and play a role in initiating the adaptive immune response by displaying antigens from pathogens on their surface.

How do B cells and T cells differ in their development and maturation process?

B cells mature in the bone marrow, while T cells migrate from the bone marrow to the thymus where they mature. The thymus also educates T cells to recognize self and non-self, eliminating most T cells that do not pass this test.

What is the significance of the thymus in the development of T cells?

The thymus is where T cells mature and are educated to distinguish between self and non-self. It is also known as a 'deadly university' because it eliminates a large number of T cells during this process.

What is the process of phagocytosis and how does it relate to the immune response?

Phagocytosis is the process by which phagocytes engulf and digest pathogens. It begins with the attraction of neutrophils to the site of infection by histamine released by infected cells, leading to the engulfment and destruction of pathogens.

Outlines

00:00

🛡️ Introduction to the Immune System

Andre, the host of Med School EU, introduces the immune system as the final major organ system in the anatomy and physiology unit. He emphasizes its complexity and the limited understanding we have of it compared to other systems like the brain. The immune system's primary role is to protect the body from diseases and infections, and it operates continuously. Andre explains the immune system's distinction between self and non-self using glycoproteins, which are crucial for avoiding autoimmune diseases. The video will cover both the innate and adaptive immune systems, with the innate system responding immediately to infections and the adaptive system providing a stronger, memory-based response.

05:01

🔬 Cells of the Immune System

This paragraph delves into the various cells that make up the immune system, divided into lymphoid and myeloid cells. The myeloid cells produce different types of cells, including neutrophils, eosinophils, monocytes, mast cells, basophils, dendritic cells, and macrophages. The focus is on the roles of macrophages, neutrophils, and monocytes, which are phagocytes that engulf and destroy pathogens. Lymphoid cells, which include B cells, T cells, and their various subtypes, are part of the adaptive immune response. The video will further explore these cells' functions in the next installment, with a particular emphasis on the myeloid cells and their role in the immune response.

10:02

🚨 Phagocytosis and the Role of Neutrophils and Macrophages

The paragraph explains the process of phagocytosis, where phagocytes like neutrophils and macrophages engulf and destroy pathogens. Neutrophils are the first responders to an infection, rapidly attacking and killing pathogens but having a short lifespan. Macrophages, derived from monocytes, have a longer lifespan and reside in organs. They play a crucial role in initiating the adaptive immune response by displaying antigens from pathogens on their surface for lymphocytes to recognize. The paragraph also describes the inflammatory response triggered by histamine release, attracting neutrophils to the site of infection, where they perform chemotaxis and phagocytosis.

15:02

🛂 The Sacrifice of Neutrophils and the Function of Lymphocytes

This section discusses the self-destruction of neutrophils after they have performed their function, which results in the formation of pus at infected sites. It highlights the sacrifice of these cells to protect the body from harmful pathogens. The paragraph then transitions to lymphocytes, which are part of the adaptive immune response. Lymphocytes, including B and T cells, are smaller than phagocytes but have a large nucleus. They are produced in the bone marrow and mature before they can carry out immune responses. The paragraph sets the stage for a deeper discussion on B and T cells' roles in the next video, focusing on their development, specificity to antigens, and the importance of the adaptive immune system's diversity.

20:03

🏫 Maturation of B and T Cells and the Function of the Thymus

The final paragraph focuses on the maturation process of B and T cells. B cells mature in the bone marrow and spread throughout the body, concentrating in the lymph and spleen. In contrast, T cells mature in the thymus, which is described as a 'university' where most T cells die, and only a select few graduate to perform the adaptive immune response. The thymus's role in educating T cells to distinguish between self and non-self is critical to prevent autoimmune reactions. The paragraph concludes with a note on the thymus's size changes throughout life, impacting the strength of the immune system as we age. The next video promises a more detailed exploration of the innate and adaptive immune responses.

Keywords

💡Immune System

The immune system is a complex network of cells, tissues, and organs that work together to defend the body against harmful pathogens such as bacteria, viruses, and parasites. In the video, the immune system is the central theme, with its primary function being the protection from infections and diseases, highlighting its continuous and vigilant role in maintaining health.

💡Lymph Nodes

Lymph nodes are small, bean-shaped structures that are part of the lymphatic system, playing a crucial role in the immune response. They act as filters for harmful substances and are the sites where immune cells are activated. The script mentions lymph nodes as part of the 'highway' the immune system uses, emphasizing their importance in the immune response.

💡Glycoproteins

Glycoproteins are molecules composed of carbohydrates and proteins that are found on the surface of cells. They serve as identifiers for the immune system to distinguish between self and non-self. In the video, glycoproteins are described as being instrumental in the immune system's ability to recognize and avoid attacking the body's own cells, thus preventing autoimmune diseases.

💡Innate Immune System

The innate immune system represents the body's first line of defense against pathogens and is characterized by its rapid, non-specific response. The script explains that this system is activated immediately upon infection and is the 'first responder' in the body's fight against invaders.

💡Adaptive Immune System

The adaptive immune system is a more specialized and targeted response to pathogens, capable of learning and remembering specific threats for a more effective response upon future encounters. The video script describes it as being activated later in the immune response and creating memory cells for long-term protection.

💡Phagocytosis

Phagocytosis is the process by which certain immune cells, known as phagocytes, engulf and destroy pathogens. The script describes this as 'cell eating' and explains that it is a crucial mechanism by which the immune system eliminates harmful microorganisms from the body.

💡Neutrophils

Neutrophils are a type of white blood cell and a primary component of the innate immune system. They are the most abundant and are rapidly deployed to the site of infection to perform phagocytosis. The video script highlights their role as aggressive and short-lived cells that sacrifice themselves to protect the body.

💡Macrophages

Macrophages are large immune cells that originate from monocytes and play a significant role in both the innate and adaptive immune responses. They engulf pathogens but also have the unique function of presenting antigens to lymphocytes, thus initiating the adaptive immune response. The script describes macrophages as long-lived cells that reside in organs and are crucial in the immune system's response.

💡Lymphocytes

Lymphocytes are a type of white blood cell that includes B cells and T cells, which are central to the adaptive immune response. They are smaller than phagocytes but have a large nucleus, which is a distinctive feature when viewed under a microscope. The script explains that lymphocytes circulate in the blood and lymph, playing a vital role in the body's defense against specific pathogens.

💡Thymus

The thymus is a gland located in the chest where T cells mature. It is described in the script as a 'university' for T cells, where they are educated to recognize self from non-self, with a high rate of T cell death during this process, ensuring that only those capable of correctly identifying threats survive to contribute to the adaptive immune response.

💡Autoimmune Diseases

Autoimmune diseases occur when the immune system mistakenly attacks the body's own healthy cells. The script explains that this happens when immune cells fail to recognize self cells as non-threatening, leading to conditions where the body's defenses turn against itself, causing various health issues.

Highlights

Introduction to the immune system as the last major organ system covered in the anatomy and physiology unit.

The immune system's primary function is to protect from disease and infections, highlighting its continuous and crucial role in maintaining life.

Explanation of the immune system's complexity and the vast amount of unknowns compared to other systems, particularly the brain.

The immune system's distinction between self and non-self using glycoproteins for recognition to prevent autoimmune diseases.

Division of the immune system into innate and adaptive components, with the innate system providing immediate responses and the adaptive system offering a stronger, later response.

Description of the immune system's cells and their development from hematopoietic stem cells into lymphoid and myeloid cells.

Role of phagocytes, including neutrophils, macrophages, and monocytes, in engulfing and eliminating pathogens through phagocytosis.

Differentiation between neutrophils, which are the most abundant white blood cells, and macrophages, which have a longer lifespan and a role in initiating the adaptive immune response.

The process of phagocytosis, starting with the release of histamine and the attraction of neutrophils to the site of infection via chemotaxis.

Mechanism of self-destruction in neutrophils after depleting their energy, contributing to the formation of pus in infected areas.

Introduction to lymphocytes, which are part of the adaptive immune response and include B and T cells.

The maturation process of B and T cells, starting in the bone marrow for B cells and in the thymus for T cells.

The thymus's role as the 'university' for T cells, where most T cells die during the education process to ensure they can recognize self from non-self.

The decline of the thymus's function after puberty, which contributes to a weaker immune response as we age.

Upcoming detailed discussion on the innate versus adaptive immune response in the next video.

Transcripts

[Music]

hi everyone my name is andre and welcome

back to med school eu

and the topic of today's video is going

to be the immune system so this is the

last major organ system that we'll be

covering in this

unit of anatomy and physiology there is

one more to go after this but it will be

covered fully in this stage it will also

involve the homeostasis unit therefore

this is officially the last uh organ

system that we will cover

and this is the last topic that we're

going to talk about in terms of anatomy

and physiology however it will pertain

uh

several

videos because the immune system is so

complex and there's so many things we

don't know about it there's so many

things we do know about it

we're going to have to keep this very

brief very short and just include the

things

in the

surface level just the tip of the

iceberg so to speak because this is one

of the most

uh

less understood systems that we have

after our brain

and uh

therefore there won't be too much

that we're going to have to cover

because it goes extremely extensively

and very complicated

but in terms of high school knowledge

there's going to be limited things we'll

have to know so just to overview what

the immune system is is of course it

protects from disease it protects from

infections

and that is its primary functions it's

the things that keep you alive the

immune system

is continuously functioning it is always

alert it is always

working

and it is something that keeps us alive

and it's extremely important there's a

lot of organs that are involved

in response with the immune system

but the major kind of highway that it

uses is the lymph

nodes and and the lymph system now the

cells of the immune system that are used

to attack pathogens they must recognize

what is self

and

what is non-self because if

the

immune cells are going to recognize the

self

cells

as uh as non-self they're going to

recognize them as enemies and then

they're going to attack them and when

this occurs when the immune cells attack

the self so they attack healthy cells

this causes autoimmune diseases now the

question is how does the immune system

recognize self from the non-self and

typically that is done with

glycoproteins so healthy cells are

are going to have the surface receptors

so they're going to have little

receptors on their cell membranes

they will be sticking out that will be

signaling it's the cells and these are

formed by glycoproteins so it's

a combination of

sugars carbohydrates and proteins and

these molecules will be there to

indicate to

the large phagocytes

that they cannot just come in and eat

them

because they are self they are

allies they are part of the same system

whereas

a bacteria would come in it would have

different glycoproteins

on its surface and therefore the cells

of the immune system would recognize

that and they would perform phagocytosis

to remove them

from the body now another important

thing to mention about the immune system

is that it's composed of two parts the

innate immune system and the adaptive

immune system now the innate immune

system is something that responds

immediately as soon as an infection

occurs let's say you cut your finger and

you have bacteria that are on the knife

that you cut your finger with they're

going to enter inside and even the

bacteria just from the surfaces are

going to enter inside

of of your skin

and inside the body and the immune the

innate immune system is the one that is

going to respond immediately and begin

the fighting process now the adaptive

immune system is something that occurs

later on if the help is needed the

adaptive immune system

will be able to be activated by the

innate immune system

and the adaptive immune system is much

stronger response and it creates

things like memory cells in order to

recognize

these sorts of attacks

later on if they occur

again and again so

typically the innate immune system what

happens is it

is the first responders kind of doing

like cpr first aid and the adaptive

immune system is the hospitals

and the clinics that are able to assess

the patient further do

operations and other things like that so

that's the two ways of thinking about

the immune system as it pertains

as it has two different parts and two

different types of responses

these responses will be covered in the

next video there will be too much to

cover in one video if we talk about

everything that is involved with the

immune system so i decided to split it

up into two videos the first video we'll

talk about an overview of the immune

system we'll mention the cells that are

involved and what they do and then the

next video we're going to talk about the

innate versus the adaptive immune

response so let's take a look at the

cells of the immune system so this is

the complete division of the cells of

the immune system there's quite a lot

however we're just going to cover the

names of these and briefly what they do

and

of course we're not even going to

include

a lot of the cells that are

part of this diagram i just wanted to

show how complex the immune system is

and how many different types of cells

that actually

involve so

we begin with the

hematopoietic

stem cell so that's the stem cell right

here

this stem cell is the one that develops

the rest of the cells of the immune

system now the stem cell would split

into two types

of cells and there's generally two types

of

cells

in the immune system they all fall under

these two categories as you can see

based on

the diagram

on the top here we're going to have the

lymphoid cells and at the bottom here

we're gonna have the myeloid

now the myeloid cells are going to

produce five different cells and i want

you to note that the way they actually

look they've got this

weird uh nucleus so the one on the top

is called the neutrophil the one in the

middle is called a cinephil and the one

here at the bottom is a monocyte now the

other two cells that are made directly

from the myeloid

is going to be a mast cell and a

basophil and finally from the monocyte

we would produce

the dendritic cell so the one that has

all these sticky pointy pointy sides

that's the dendritic cell and a

macrophage so the two cells that we're

definitely going to talk about are going

to be the macrophage

and the neutrophil and a little bit

about monocytes as well

now if we're looking at the lymphoid

cell and what uh what type of cells are

made out of that

we're going to have b cell precursor to

b cells

so b cell

pre we're going to have a killer cell in

the middle here and

the one on the side there is a t cell

precursor

now from the t cell it's going to

produce

three different

t cells it's going to produce memory t

cell we'll have a cytotoxic t cell and

the helper t cell and from the b cell a

precursor we're going to generate memory

b cells and a plasma cell

so we're going to discuss all of these

but primarily they will be discussed in

the second video we're just going to

quickly mention about b cells and t

cells in general and for the most part

we're going to talk about the myeloids

monocytes

neutrophils and macrophages so the

immune system is split into two types of

cells as mentioned we've got the

phagocytes

and the lymphocytes lymphocytes would

include b cells and t cells phagocytes

would include neutrophils macrophages

and the monocytes so let's discuss

monocytes or and or the

phagocytes first

phagocytes

are cells that do phagocytosis

in phagocytosis meaning that it's going

to engulf cells it's called cell eating

so basically when a bacteria or a

pathogen or microorganism comes along

that where it shouldn't be

in the body

the

phagocytes that the cells are going to

attack it and they're going to engulf it

dissolve it and get rid of it now these

phagocytes are produced and stored

in the bone marrow phagocytes are

typically scavengers

so they're going to go all around you

know throughout the body

and what the their major function is to

remove dead cells

and

to remove invasive

microorganisms so they would be called

scavengers

kind of searching around the body

looking for

microorganisms that shouldn't be there

and looking for dead cells to clean them

up now let's talk about neutrophils and

macrophages the the two major types

of phagocytes the neutrophils

make up 60

of white blood cells in in the blood so

primarily the blood is composed

and the white blood cells are composed

primarily of neutrophils

and they circulate the patrol throughout

the body so their main function is to

patrol and when an infection occurs

we are going to have a response and this

is going to be an an anatomy response

and during this infection

plenty of neutrophils are going to be

released in great numbers

and they're going to vigorously attack

the pathogens that have entered the body

so they're very vicious they they kill

rapidly

however they have a very short

life span so these cells actually do

the phagocytosis

now if we talk about macrophages they

are originally made in the bone marrow

as monocytes

so we discussed monocytes lead to

macrophages

and so originally it is made in the bone

marrow as monocytes

then

the monocytes are going to circulate

around the blood and as they leave the

blood they're going to develop into

macrophages

as they settle in organs so they

typically reside in organs they have a

long lifespan so they are long lived

much longer

than the neutrophils but also going to

be viciously dissolving

different microorganisms that enter the

body

as part of the immune response

but the difference is they do not

directly destroy

the

pathogens

fully and what i mean by that is

they play a role in initiating the

adaptive immune response

by

cutting pathogens and displaying their

antigens or displaying little pieces of

the pathogens on their surfaces

that can be recognized by the

lymphocytes and lymphocytes are part of

the cells the b and the t cells that are

part of the adaptive immune response and

we're going to talk this in more detail

in the next video but i wanted to just

give you a quick introduction because it

is part of the duties of the macrophages

it's their function to initiate and to

they play a crucial role in initiating

the adaptive immune response

by

not simply dissolving the pathogens

completely but what they're going to do

is they're going to cut them into pieces

and they're going to display

their antigens on their surface

therefore

the b cells and the t cells are able to

find them and bind to them and

begin dividing and initiating the

adaptive immune response so what is

phagocytosis and how does it actually

occur so

we have to begin with an infection

of the body so when infection of the

body occurs

we're going to have cells that will be

under attack

and they're going to release

histamine now once the cells are being

destroyed by the infection of

microorganisms like bacteria or viruses

they're attacking our healthy cells some

of them are going to release histamine

histamine is an inflammatory chemical

and it's going to spread all around the

body as it

kind of signals

and it

is going to go to the bloodstream it's

going to go to the lymph nodes and it's

going to signal that there is an

infection going on there is cells dying

there is trouble

the

immune system must come and help the

first responders of course

the neutrophils are going to be

attracted to the histamine call so

neutrophils are going to be those first

responders that will get to the site

also the site is going to be flooded

with with blood and water and different

substances

and that is part of the inflammatory

response that we will talk about

in the in the next video however what i

wanted to point out here is how this

phagocytosis begins and how it happens

so

once this neutrophils are arrive at the

site of infection because of the call of

histamine

and this

whole process is called chemotaxis

because it is a attraction of this

chemical

neutrophils attraction to the chemical

that promotes the neutrophils flooding

into the area then the neutrophils are

going to engulf

the pathogen

via phagocytosis so that's going to be

endocytosis they are as you can see in

this diagram they're going to wrap

around the bacteria and they're going to

fully surround them and fully engulf it

in its own

cell and once inside the cell the

the lysosomes that are inside the cell

are going to release

enzymes they're going to release

digestive enzymes an example of

digestive enzymes that they release are

going to be proteases and after several

kills

from the neutrophil they are going to

deplete their batteries they're going to

deplete their energy and the neutrophil

is going to do self-destruction it's

going to kill itself

and all of those neutrophils that are

going to die and they're going to kill

themselves they form this pus that we

get from an infected area that is the

action of neutrophils sacrificing

themselves to keep you

alive from the dangers of rapidly

dividing bacteria or rapidly dividing

viruses

or or other parasites and pathogens that

may enter the body

now let's talk a little bit about

lymphocytes and that's typically

lymphocytes are part of the adaptive

immune response

they are the classic b and the t cells

and

lymphocytes are going to be smaller

than the phagocytes

however they're going to have a much

larger nucleus so the nucleus is going

to fill up almost the entire cell

as their distinctive feature when you're

looking through a light microscope

and there are two types that we are

going to discuss

the two types are b and t cells

so we will talk about the general

b and t cell where they come from and

how do they mature and then in the next

video we'll discuss more about their

action

in the adaptive immune response but in

general both

are produced in

bone marrow

so that they are born in the bone marrow

and they develop in the bone marrow

before the child's birth so while um

the

fetus is being developed the b and the t

cells are going to be forming in the

bone marrow and only mature lymphocytes

can perform immune responses so the

immune cells that are born

in the bone marrow are not mature yet

they're going to have to go through a

process before they're able to act so

only material lymphocytes will be able

to carry out

responses

of the adaptive immune system now during

the maturation process after they're

born in the bone marrow

the

b and the t cells could be made in a

variety of different ways with millions

of different combinations

and the reason for that is because there

are going to be millions of different

pathogens that can infect the body and

therefore the b and t cells

must be specific to one

antigen so from the millions of

different combinations that are possible

this is why our b and t cells are able

to

bind to a specific pathogen even if it's

never seen it before it's fascinating

how our immune system works in this way

and that's why our adaptive immune

system is just

so incredible and so diverse and so

compact

with with information that we still have

not discovered everything about it and

it's the least understood

after the brain

but once the b and the t cells are

mature they circulate

in the blood and the lymph now let's

take a look at the similarities and the

differences between the b

and the t cells so beginning with the b

cells

they will be born in the bone marrow and

they're going to mature

in the bone marrow then once they're

mature in the bone marrow they're going

to spread all around the body and

concentrate

in the lymph and the spleen now if we're

talking about t cells they are going to

mature in the thymus so they're they're

going to leave the bone marrow

and they're going to collect in the

thymus and they're going to mature in

the thymus which is

and the thymus is a gland that is

considered the university of t cells

and it is a deadly university because it

kills 98 of t cells that enter it and

basically in in terms of education what

type of education it does is the thymus

is going to educate the t cells

to

be able to recognize self and the

non-self because it's going to be

extremely detrimental if t and b cells

these very very powerful cells

are going to recognize self

and

and they will attack the self then that

could be

deadly for the body therefore the thymus

is a brutal deadly university where most

t cells are going to

die they're not going to make it and

only about two percent of t cells that

enter the thymus are going to mature and

properly do their adaptive immune

response so in the thymus this is where

they are educated now as soon as they

graduate from the death university of

thymus

they are going to spread all around the

body

and

just to

mention a couple of other things

about thymus

is that the thymus is

is basically a gland

in the chest beneath the sternum

and it grows two times its size from

birth to puberty and then afterwards

after puberty it's going to shrink so

this is why our immune system is not

going to be as responsive it's not going

to be as strong

as we age past puberty so this concludes

our first video on the immune system in

the next one we are going to talk about

the anatomy response versus the adaptive

immune response in greater detail

[Music]

you