Anatomy & Physiology Tissues

Hi and welcome back to www.educator.com.0000

This is the lesson on tissues.0002

When we say tissues we are not talking about blowing your nose kind of tissues.0004

We are talking about a bunch of cells together with some common purpose or functional goal in terms of what they are doing for your body.0010

These cells organized into group for a specific set of functions or purposes.0018

Sometimes for just one purpose but a lot of times it is many.0023

Epithelial tissues are the first we are going to talk about.0027

An epithelium is always cells that are on the outermost, the most superficial layer of an organ or the innermost part or deepest part of an organ.0029

If they are on the innermost parts that organs has some kind of passageway or hallow area called the lumen.0042

The cells on the innermost part or those epithelial cells are helping to move something through,0049

absorbing and secreting chemicals, it could be variety of things.0055

An epithelium is very important to our body.0060

Connective tissues are the most abundant tissue in your body.0063

Connective tissue is a lot of different kind of cells functioning together.0068

It does connect your body parts to each other and help bind organs to neighboring tissues.0072

Muscle tissue and neural tissue are technically a type of connective tissue but are major tissues in the body.0079

You are going to find muscle tissue all through out the body even in the parts where you do not realize it is there0086

because some of the muscles are doing involuntary actions that you do not directly control consciously.0091

The muscles are in your dermis, in your skin, that you do not consciously move but they do contract and relax.0097

Neural tissues are also all through out the body.0107

It is not just the brain, not just the spinal cord, we are talking about every single nerve, all the neurons, billions of cells.0111

Histology is a very important kind of branch or study related to anatomy and physiology, that is the study of tissues.0120

We know that it is looking up close at a tissue to see what the cells look like and how they are oriented related to each other.0129

That is why it is typically with the microscope that you are going to be looking at histological picture.0135

Later on in this lesson we will show you a histology slide.0140

The first kind of tissue that we are going to be talking about is epithelial tissue or also called epithelium.0144

The purpose of the epithelium is to cover every external and internal surface of the body.0152

Not just on the outside but internal organs as well.0157

These epithelial tissues are always attached to a basal lamina also known as basement membrane.0160

That is the synonym for this term.0170

Here is what we mean by that.0174

You are going to see pictures that we draw for you or have displayed on slide later on in this lesson.0180

It is always cells bound to look like just a line.0184

It looks like a cement line that the cells are attached to or anchored to.0189

That basement membrane or basal lamina is made of cells.0195

Think of it like organic protein glue that is anchoring all of those cells to those surface.0200

That basal membrane is connected to what tissue immediately below or deep to it.0208

You are going to find basal membrane associated with epithelium.0214

Also epithelium is a vascular.0217

It gets nutrients and gas from diffusion and osmosis.0220

What is a vascular means specifically?0223

Let us take the cardiovascular system.0226

It always has to do with transporting fluids.0231

First is a vascular plant like a tree, it is called that because the tree is able to suck water up and get it up through osmosis to the top of its leaves.0234

We are vascular because we are able to move fluids against gravity all through out our0244

body but the specific tissue is a vascular because when you look at blood vessels and the transport of fluid related to this, the blood vessels do not go right up into it.0250

You are not seeing capillaries, those tiny bundles of super bodies feeding this directly with oxygen nutrients.0262

The oxygen in nutrients, that gases that are going to be given to these tissues get there from whatever tissue right next to it.0268

It is diffusion and osmosis that is getting the nutrients and gases to the epithelial tissues.0276

Because we are talking about the parts that are on the very outside of your body, the passageways that you are swallowing stuff into or inhaling air into,0282

they are consistently damaged by a wide variety of environmental factors regenerating with stem cells.0293

You are getting pretty much regeneration of these epithelial tissues depending on where they are in the body.0300

Let us take the epithelium in the surface of the tongue.0306

It needs to be regenerated a lot because every time that tongue cells get rubbed against by something you are chewing or eating, you need to replace those.0309

It is same with the epidermis or the outer parts of your skin.0320

You need to regenerate them as it gets damaged.0324

Those are the characteristic of epithelial tissues in general.0330

They are named based on cell structure and shape and is it one layer, two layers, or many layers?0333

Let us look at some examples.0349

A simple squamous epithelium, why is it simple and why is it squamous?0351

Simple has to do with how many layers.0355

This means one layer.0359

That is how simple as it gets.0361

Later on you are going to see a stratified, it is the opposite of one layer.0363

We are talking about many layers on top of another.0370

Squamous means round or disk like.0374

They look like that.0383

That is a squamous cell.0389

One layer of round or disk like cells.0390

That is what simple squamous epithelial is.0393

You are going to see more detail about that later on in this lesson.0395

Here it is simple squamous epithelium.0400

One layer of point shaped cells that look like this.0402

It is mean for areas that need a high rate of diffusion and osmosis through the cells.0408

Think about inhaling air or transporting nutrients to blood vessels, you want to get the oxygen to your cells as quickly as possible.0414

You want to get nutrients like sugar, proteins, and fats as quickly as possible.0422

You do not want to have them drift through layers of cells it would take longer and harder to get that stuff around the body.0428

Two examples are the alveolar walls and capillary walls.0434

Let us see.0438

Here is a good picture of how they look.0439

Let us say we were to take a capillary which is the tiniest blood vessel type in the human body.0442

If you were to cut that capillary down the middle and we can look down it with a microscope, the cells would be one cell thick0448

simple and squamous because if look from the outside of it you see all these disk like cells that make up these.0460

I am also going to draw a little nucleus.0468

Since it is a one cell thick, what a capillary does is it gets oxygen to the tissues around it so you get a very quick diffusion0474

which is a passive natural movement of gases and nutrients out of the capillary into the tissue and vice versa with CO2 and waste and it will take it back to the lungs.0483

Having one cell thick is great for quick diffusion and osmosis.0497

In alveolar walls, if you look at the capillaries in the lungs you want to get CO2 out of the capillaries and into the passageways of your lungs and vive versa with oxygen.0500

The microscopic bubbles that make up the alveoli of your lungs, you have hundreds of thousands of these sacs.0513

They are also one cell thick.0521

Here is an alveolar bundle if you take a cross section through the alveolar bundle it is also one cell thick.0525

It is brilliant in terms of getting oxygen that you inhale to your lungs into the capillaries quickly and efficiently.0536

That is ideal for diffusion and osmosis.0544

Stratified squamous epithelium we still have those round, plate looking cells, but a stack of them, many layers of it.0550

It is meant for areas that have to deal with a lot for friction and rubbing like the epidermis of the skin0560

it is being touched and you need to regenerate those cells because you are going to lose them.0569

The esophagus is the tube that takes food from your throat area down to your stomach every time you swallow a chunk of food.0575

It is rubbing against the inner part of that esophagus and it is called the mucosa.0585

You are losing those cells and you need to be able to regenerate that epithelial tissue.0590

The vagina or anus you have friction to those areas depending on what activity you are engaged in.0594

You got to be able to regenerate these epithelial tissues because of those environmental sources of friction.0601

Here is a little image of what they look like.0609

You could see that they are still roundish and as you get towards the surface, the superficial part of it, this could be the epidermis of the skin.0611

It makes sense that these flatten cells here were worn away from the top and down here, the cell division of these0620

in the sense of stem cells are going to be providing the new cells that gradually move away from the blood supply down here.0625

This black line down here this is the basal lamina or basement membrane.0632

This is stratified squamous epithelium ideal for friction or protection.0639

Here is the histological slide of part of the esophagus and stomach connection.0645

These are some actual micrographs which mean photographs taken with a microscope.0651

This is something close.0657

This passageway is the lumen of the lower part of the esophagus or the most inferior part of the esophagus.0659

Here is the beginning of the stomach and here is the lumen of the stomach.0666

You are going to have mucosa lining that inner part of that stomach.0671

You are going to have some mucous glands that are going to be on the esophagus but0675

we also need to have stat on the inner most part of the esophagus is lot these stratified squamous epithelium.0681

You could that there are stacks and stacks of those round cells because every time food is rubbed against it, it is going to damage parts of it.0692

The mitosis down here is bringing up new epithelium here.0699

You are going to see all kinds of epithelial tissues in the stomach.0704

For instance, right here you got some glandular epithelium.0707

You are going to here about that later.0711

These are secreting gastric juice and all those little chemicals and molecules inside the stomach to help with the digestion process.0712

Another kind of epithelium is simple columnar.0720

This is one layer because it is simple and column shaped cells like its name says.0725

It is meant for absorption and secretion typically.0729

It depends on what specific organ it is in.0732

Sometimes they are absorbing something or they are taking something in from the passageway or they are secreting something in to that passageway or lumen.0734

Sometimes they have what is called microvilli and I will draw some microvilli for you here.0743

They look like little hairs on the surface.0749

Epithelial cells are known as cells with polarity meaning that one end of the cell usually0755

functions a little bit differently than the other end in terms of the look in the structure.0762

You could see with the simple columnar down here this is the anchored part of the cell that is going to be adjacent to the base membrane.0767

Up at this end if we are talking about space or lumen, this is the end that actually doing the absorbing or secreting.0775

These little microvilli are going to be looking like this.0783

For instance, in the lining of the stomach and intestines you have to be absorbing and secreting stuff.0786

If we take the small intestine, you have the ability to further the process of digestion.0794

The small intestine is a very long tube in the body that is doing absorption.0801

These cells are perfect for that.0805

Stratified columnar is very similar to the previous picture but you are going to see stacks of these cells.0808

These also have cell on the top but not necessarily.0832

Stratified columnar epithelium is many layers foam shaped cells and meant for protection.0841

Similar function to that stratified squamous epithelium but the cells are shaped differently.0848

The location is the epiglottis.0853

The epiglottis is a flap that comes down on the entrance to the airway to your trachea every time you swallow.0855

Often times, when human being is swallowing they are getting food or liquid down into the digestive track.0864

You do not want it going down into the lungs.0869

The epiglottis is a nice flap that protects us from aspirating on something other that air.0872

The anus and urethra also need protection based on what is going through those areas.0878

Pseudostratified columnar epithelium, pseudo meaning fake or false, stratified meaning many layers and columnar shaped.0886

It is a false stratification because it appears to be layered but it is one layer of palm shaped cells.0896

The reason why it appears to be layered is that varying heights of the nuclei giving the illusion of being many layers.0903

Let me draw you a picture.0911

Sometimes you will get one of them being smashed in like that.0916

I will do another one that is smashed in.0923

You can see that this is one layer of epithelium of column shaped cells but you will see this.0931

Because you have varying heights of nuclei at first glance you might think that is 2 layers but it is not.0940

It just appears that way and sometimes this have cilia.0952

I have mentioned cilia on the other side but let me explain more here.0956

Similar to microvilli the difference is that cilia are helping dress something along rather than absorbing or secreting.0965

Think about the lining of the trachea and bronchi, these are tubes associated with breathing in air and exhaling.0977

You generate mucous in your lungs and if it was not for the sweeping up or brushing up of mucous you can drown in your own fluid especially when you are sick.0983

The brushing up of that mucous that is generated on the passageway of your lungs is very important.0997

In the trachea and bronchi you are going to see lots of cilia brushing up mucous.1003

Simple cuboidal epithelium is one layer of cube shaped cells meant mainly for secretion and absorption.1008

Secretion, absorption, or protection or SAP that is the way I remember it.1017

Those are the three major functions of epithelium.1023

Those are the big three you are going to see a lot.1027

Secretion, absorption, protection, one or the other or some combination of the three.1028

When you look at the kidney tubules, the little tubes that help make you urine you are going to see this.1033

The thyroid gland which has a lot to do with regulating your metabolic rate these secrete hormones into your blood stream.1041

These two definitely have simple cuboidal.1048

If you look at one of the passageways to which urine or thyroid glands secretion are found, you are going to see cube shapes.1051

They are not quite round and squared off edges and here is the nuclei.1064

This is your average looking kidney tubule epithelium.1071

You could see that it is good for secreting and absorbing stuff easily makes thing go in and out.1076

It is same as simple squamous epithelium except for the cell structure.1082

It make sense that you can easily have secretions going in and absorbing through this as well.1088

Stratified cuboidal is similar to just what I drew except that they are just one layer you are going to see additional layers of these cube shaped cells.1097

I am not going to draw all of them.1110

You are going to have stacks of them.1112

It seems stacks next to tubular structure or luminous, this is called stratified cuboidal.1116

It is meant for secretion, protection, and absorption like I have said earlier.1131

The lining of sweat glands like in the dermis of your skin often times if you cut through it1141

and you look at it under a microscope that histological view is going to show you stacks of cube shaped cells.1148

Transitional epithelium is meant for stretching and recoil.1155

You have certain structures in the human body, certain organs where you need to expand and then go back whatever what is inside that is left.1160

When relaxed, it looks a lot like columnar.1167

Here is your relaxed transitional epithelium like the lining of the urinary bladder or uterus.1171

When relaxed they look like that then when it is stretched let us say the urinary bladder has closed to urinating that means that person need to urinate.1187

It is stretched quite significantly.1202

When you stretched out those cubed shaped cells they do not look cubed, the column shaped cells they do not look columnar anymore because they are stretched.1204

That is a big difference between this and this.1223

Think about any organ that is meant to expand.1231

The urinary bladder has urine in it.1234

You got to stretch the uterus when you have a baby.1239

I will tell you about glandular epithelium.1242

It is meant for producing and releasing secretion.1245

Anytime that you have a gland whether it is releasing a secretion outside of the body into a body cavity1248

it is made of glandular epithelium in terms of the production that is being secreted and the act of secreting it.1255

The three main types of glandular epithelium are merocrine, apocrine, and holocrine.1261

I remember this mnemonic device MAH and the reason for that is because the order will help you remember what this one.1267

You will see why.1277

The merocrine type an example is salivary glands.1279

Here we have the different types of salivary glands that is three pairs total of 6 salivary glands in humans.1282

You got the peroded, sublingual, submandibular, and all of these have the glandular epithelium that is the merocrine type.1290

Merocrine secretes just a little bit of substances from the cells.1299

The cells in the epithelium are not leaving just bits of the substance.1304

For example, let us say this is the gland and here is the opening in which the secretion actually comes into your mouth.1308

Along the edge of it, you have cells that are responsible for producing saliva and secreting it into the cavity or the lumen.1317

Secretion into here or exits in the opening of the mouth to help you dissolve things you are eating.1328

They are little sacs or vesicles and inside you have water and enzymes.1342

These little sacs will fuse with the edge of the cell and you will end up getting water and this enzyme package exiting.1353

That is saliva.1368

If you remember that merocrine is the smallest bit of secretion.1370

You will see that with apocrine it is a little bit more.1375

When we look at apocrine glandular epithelium an example is mammary glands.1378

The glands that release milk.1382

When we look at a mammary gland you will see it is a little bit different.1385

Here the cells that are lining that actual lumen or opening.1390

Instead of being little pockets that are released, they are actually parts of cell but not the whole cell.1397

Here is what it look like.1404

You would have this organelles and parts getting rid of the section of the cell and all this little cell parts together make up the milk.1406

All those carbohydrates, proteins, lipids, hormones, etc, they are in breast milk.1428

Apocrine is a little bit more is released, not just little pockets but parts of cell.1434

Then we will look at holocrine, sebaceous glands we will look at hairs there are glands adjacent to the base of the hair shaft near the follicle.1440

They release an oily substance to help coat and protect your hairs.1458

Holocrine helps in secretion in terms of the amount that is released.1464

Hol means whole, like a whole cell.1471

The MAH that I have mentioned before, the merocrine releases little bits, apocrine releases parts of cells, holocrine releases whole cells.1479

This is the lining of the gland here, the sebaceous gland.1489

You will see the whole cell being released as a part of that oily glandular secretion.1495

Those are the three different name types of glandular epithelium.1502

The connective tissues this is an important tissue in the body.1505

It is the most abundant tissue.1511

It is all over the place.1513

It is connecting the body parts to each other, stabilizing the body, giving it structure and stability.1514

It is meant to connect and bind together all the organs and organ systems to form a cohesive and cooperative body as a whole.1520

Any of the different skeleton here and here, on the far right, we got a gorilla, chimpanzee, gibbon, orangutan.1527

Whether you are looking at a monkey or ape, or human, the skeleton is made up of connective tissue.1537

When we look at connective tissue, anything that is found through out the body helping to1550

bind organs to each other, helping the body to communicate with itself, it is a connective tissue.1555

When you think about bones, it connects the body parts to each other.1562

If it was not for your bones, you will not be alive.1566

Connective tissue is made up of fibers and cells.1571

First we will talk about the fibers.1577

The fibers are made up of protein.1579

Protein is the most abundant substance, you are going to move all the water from the body, protein is the next most abundant substance.1580

Collagen fibers are the most abundant protein in the body.1589

It is a bundle of protein humans that are slightly flexible.1594

They are typically strong and arranged in one direction.1598

A good example of that would be tendons.1602

Tendons help connect muscle to bone.1605

Ligaments help connect bone to bone.1609

A tendon like the calceneal tendon or the Achilles tendon if you think about how it connects your calf muscle to your heel, that Achilles tendon is a bundle in one direction.1611

It is very tough and strong and slightly flexible because anytime that you contract that muscle you are going to be pulling up on your heel.1630

When you relax it, the opposite is going to happen.1643

All of those are aligned in one direction help keep it stable, connect that muscle effectively to that bone.1645

It is very strong and anyone who has snapped that tendon knows it is very painful and they will realize how important that tendon is.1651

Typically when it snaps away from the bones surgery is required to reconnect it.1661

Collagen fibers are not just tendons and ligaments, it is found all through out of your skin.1665

It is in your bones.1671

It is very important.1672

Elastic fiber is another example that connects the tissue fiber.1674

This is not quite as strong but a lot more flexible.1677

A bundle of protein units that are very flexible and elastic.1682

It is strong but not quite as strong as collagen.1686

An example is intra vertebral disk.1691

Intra vertebral disk if you look at the vertebrae, this side is the anterior side towards the front of your spine bones and this is the posterior or dorsal side.1694

This will be that little bony extension that makes up those bumps you see in someone’s back when they bend over.1715

This is a little process that connects to the ribs and also muscles can connect there.1723

This bone on the top and bottom of it you are going to see a disk.1730

That is why it is called inter vertebral disk because they are in between the vertebrae.1738

It has to be flexible.1743

They have to have some give in elasticity because think about when someone jumps off of1745

the ledge the force of the bones coming together when you hit the ground, you will have that cushioning.1750

You do have slight elasticity there.1760

As time goes on, the integrity of these and thickness can drop a bit and that is why some older people get a little bit shorter.1763

My grandmother is used to be being close to 5 ft now she is more like 4’10.1776

We can blame some of those intra vertebral disks for that little drop in height.1781

They are made up of these elastic fibers and a good example of elastic fiber is the name elastin.1786

You are going to find that in those inter vertebral disks.1794

Reticular fibers same sub units is collagen but not in one direction not like in tendons we have1797

the collagen lined up in one direction because that is how the muscle contracts.1804

It contracts along one point back and forth.1809

With reticular fibers, reticular means net and if you took biology you will remember that1812

the endoplastic reticulum that organelle in the cell looks like little net next to the nucleus.1818

Reticular fibers they are net like.1825

A good example is inside the liver.1828

These net like fibers are found through out the liver to help keep it together and keep it stable.1830

You would not want collagen fibers to just line up along one direction of the liver but you want them spread out all through out the tissue to help give it stability.1836

Those are connective tissue fibers.1849

Connective tissue cells are another important part of connective tissue.1851

When you get a cut in your skin, fibroblasts are helping heal back the cut and remake those proteins to help bind it together.1856

If it is not a thick cut you would not need stitches.1871

If it s a thin cut your body takes care of it and often times it would not scar.1878

You can think fibroblasts for secreting this connective tissue with fibers to help rebind those parts of the skin that has been separated.1883

Macrophages that mean big eater and these are giant cells that look like pacman.1892

They will engulf foreign bodies.1902

Let us say you got a bacterial cell that is potential harmful to your body.1905

Here is a nucleus inside of your macrophage and all these little lysosomes or little organelles1913

that have enzymes that are meant for breaking down foreign bodies.1923

Once the macrophage swallows up, that foreign body, those enzymes inside these lysosomes will fuse with the pocket that is now engulf this bacterial cell.1929

Those enzyme will break it down and get rid of it.1938

Macrophages some of them are fixed, they are like permanent resident of organs or tissues in the body.1944

Others are free, they migrate in and out.1950

The amazing thing is that these macrophages can flatten themselves and squeeze it in between the cells or tissues.1953

The ones that are free migraters are amazing how they will go in target of foreign bodies and get that immune response going.1960

Mast cells secrete a couple of different things, they secrete histamine and heparine.1968

Histamine is one of the main things they secrete and if you have ever taken anti histamine you are familiar with the opposite of what this does.1976

An anti histamine is going to get rid of the swelling especially your nasal cavity.1992

If you have a stuffy nose it is very uncomfortable and that is your body’s natural response to getting some kinds of infection or irritation on your upper respiratory tract.1997

You will get inflammation in that area to get more blood flow and try to get rid off that foreign invader that is causing the problem.2007

It is very uncomfortable so you will take an anti histamine to reduce the swelling.2013

That tells you that histamine is the cause of inflammation.2020

This is released to make blood vessels get dilated and that results in swelling.2024

Heparine is an anti coagulant.2030

That means that this will prevent or get rid off blood clots.2037

Sometimes blood clots are good thing.2042

A clot prevents more blood from exiting out of a wound but once the healing has happened2044

and you prepare the wall of the blood vessel you want to get rid off that clot.2053

You do not want it to stay there.2058

If it gets dislodged that clamp of a clot and that will cause a problem.2059

Heparine will actually thin the blood and get rid of those clots.2067

Lymphocytes are important cell of the lymphatic system and lymphatic tissue is all through out the body that is connecting body parts to each other.2071

Lymphocytes are responsible for making anti bodies and this gives rise to plasmacytes.2080

Plasmacytes helps get anti bodies to areas where you have foreign invader and anti bodies are part of that immune response.2090

Adipocytes look like giant yellowish cells and in the corner it is shed over to the side you will see a nucleus.2103

Some people say that a cross section of adipocytes looks like a pus ring because the pus membrane2114

can look a little different and yellow but inside you are going to see lots of yellow.2123

The point is that it looks like a pus ring because you have that edge and then this little nucleus2129

to the side becomes squeezed to one corner and that looks like the jewel of the pus ring.2136

I have drawn this in yellow because lipids or fats in the body are stored in adipocytes.2140

This means cells that contains fat.2149

We have all these fat gem packed inside of the plasma ring in the cytoplasm of this cell and the nucleus is squeezed over to the side because of that fat.2152

That is the typical look for an adipocyte.2164

Melanocytes they make melanin.2167

Melanin is that pigment that gives your skin hair and iris within the eye’s color.2176

These cells are found all through out your skin.2186

They are stimulated to make melanin and our genetic factors associated with that and environmental factors like UV radiation.2189

Connective tissue example when you get combinations of those fibers that I have told you about in cells that make different kinds of connective tissues.2198

Adipose tissue like I have mentioned before you are going to have adipocytes storing that fat in the body.2208

The most abundant site for adipose tissue is going to be the deepest parts of your integumentary system.2215

The lowest parts or deepest part of your skin called the epidermis is a site where you have lots of adipocytes.2223

The amount of that stored varies for most person and in different parts of the body.2230

Your buttocks area typically has a lot more adipose storage than in your hands.2236

Tendons and ligaments are made up of a lot of connective tissue fibers but you also have cells in2242

the neighborhood like fibroblasts that can reinforce or make little repairs.2250

If you tear your ACL you will need surgery to get a strong ligament in there.2255

If you have microscopic tears that causes a little bit of pain after you got that injury happen, you have cells that reinforce and remake parts of those fibers.2266

Sometimes people do not need surgery with those tiny little tears.2279

Your body can compensate for that.2283

Blood is definitely a connective tissue.2285

There are lots of blood proteins associated with this particular tissue and there all kinds of blood cells.2290

Marcophages is just a typical in terms of cells that are assisting in terms of blood flow around your body.2299

Cartilage are soft bone.2309

Cartilage found in every movable joint in your body found in the nose, ears, etc. are very important.2312

You not only have a lot of fibers associated with cartilage but cells that can produce those fibers and release them to make that cartilage.2320

Bone is a lot harder than cartilage.2330

Collagen fibers are very abundant in bone.2334

Without cells in the bone you are not going to be able to produce that collagen and maintain the integrity of your bones.2339

Muscles are made up of muscle fibers and those fibers in your muscle cells are jam packed with proteins.2349

These are just several examples of connective tissue types in human body.2359

Thank you for watching www.educator.com.2363