- [Voiceover] The category of connective tissue
has several general functions.
Now, there's not one single tissue that does all these,
but the category of connective tissue as a whole
will cover these.
So one thing they're doing is
supports softer organs of the body.
Well we know bones are connective tissues.
That's definitely supporting softer organs.
Second one, connects parts of body.
Well, does blood connect one part to another?
Sure, it transports nutrients from one another.
Stores fat.
Well, fat itself, adipose, is a connective tissue.
Produces blood cells.
Inside your bones is red bone marrow.
Red bone marrow is going to produce blood cells.
But every single connective tissue
will contain fibers and cells,
as well as this thing called an extracellular matrix.
Fibers are what gives them flexibility,
but retains strength.
Cells, well, that's what the living part is,
and this non-living extracellular matrix.
This is gonna be everything found in between the cells.
Could be liquid, could be solid,
could be minerals, could be whatever.
Anything non-living in between the cells.
And some of these tissues can have a lot of space
in between the cells.
The matrix itself can provide a ton of strength.
In the case of your bones,
the matrix is filled with calcium.
The calcium provides a ton of strength
in conjunction with the fibers.
Now we have two general types.
We either have a fibrous connective tissue,
or some special ones.
The special ones are unique
and really don't have their own category per se.
All right, so first off,
provides strength and elasticity.
Well, the strength can come from the matrix,
it can also come from the fibers.
Elasticity, they move.
Good thing about your nose or your ears.
Your nose and ears contain cartilage.
Cartilage is going to be slightly mobile.
But then think about tendons and ligaments.
Well, those tendons and ligaments
don't really move too much,
but got a ton of strength,
they do give just a little bit.
Some of the cells you'll find are called fibroblasts.
The fibroblast is the main cell
of your fibrous connective tissue.
We know they're fibroblasts because the blast at the end
is what makes the tissue.
For example, fibrocyte, C-Y-T-E,
will be the ones that maintain it.
They just keep it healthy.
Macrophages.
Think of these as your garbage disposals.
They're gonna go around
destroying whatever shouldn't be there.
Lymphocytes.
Well there's that C-Y-T-E,
so we know that's a cell that's maintaining,
it's helping keep alive.
Lymphocytes and nuetrophils
are both types of white blood cells.
It's gonna help to protect, to keep it safe,
get rid of any form of particles,
invaders that shouldn't be there.
Our three types of fibers,
collagen, elastic, reticular.
I'm willing to bet you can probably figure out
which one of those three has the most flexibility.
And it's sure elastic.
Elastic is meant to stretch,
while collagen has a very high tensile strength.
It's very strong.
You can kind of think of collagen
an equivalent of your steel girders in a building.
If you have the same size steel fiber,
and the same size collagen fiber,
we're talking microscopic here,
they'd have almost the same amount of strength.
Reticular fibers, well they're similar to collagen,
but they're thinner.
Because they're thinner,
that means they're not quite as strong.
So collagen's the strongest,
elastic are the weakest and most flexible,
reticular, they fall in the middle somewhere.
So here's an artist's rendition of connective tissue.
Talk about looking like a mess.
Can you see those
kind of almost peach colored or pink color
or collagen fibers there?
The thin blue strands,
those ran through our reticular fibers.
You're gonna see the kind of squiggly peach-colored ones
are elastic fibers.
You have fat cells in here,
you have neutrophil cells,
you've got tons of things.
All interwoven together.
And all that space in between,
everything in between the cells,
is your matrix, or known as your ground substance.
So here's an example of loose areolar connective tissue.
Now if you notice, is you have thick and thin fibers,
you have a couple of cells scattered throughout,
those little purple spheres are cells.
So we have our cells,
we have a lot of space between the matrix,
and there is no order.
Completely random.
You can look at tissue upon tissue,
they will not be the same.
The similarity is the randomness.
Dense connective tissue.
Now can you kind of see that wavy pattern?
All those waves, all those lines,
are gonna be collagen fibers.
That means we've got a lot of strength in here.
So all those waves, all those collagen fibers,
are running in the same direction.
That means a lot of strength
if you pull along the fibers,
so you pull them left to right.
But you notice there's no fibers
running up and down in this picture?
That's because these are your tendons and ligaments.
Tendons and ligaments are only pulled
or stretched in one direction.
They don't need the strength of the fibers running
in multiple directions.
Just kind of wavy pattern, these collagen fibers,
over and over.
That's dense connective tissue.
Then we can move on to some kind of specialized ones.
Moving to cartilage here.
And I mentioned cartilage before,
with the different types of flexibility,
but let's look in more detail what they are.
Cartilage is produced by the cells called chondroblasts.
Now, these chondroblasts are found in structures
called lacunae.
You can kind of think of lacunae as a house.
The chondroblasts live inside of lacunae.
But there's a little catch.
The chondroblasts are under house arrest.
They can not leave lacunae.
So chondroblasts are inside the structure of lacunae,
and they cannot leave.
The unique feature of cartilage,
is they do not have any blood vessels.
It's one of the reasons why
it takes cartilage so long to heal.
There's no blood in the tissue to help it heal.
Plus cartilage has a real high amount of collagen.
So a lot of strength, but still no flexibility.
So here is cartilage.
You can kind of see that purple hazy?
That is going to be the ground substance,
or the matrix.
All of those reddish pink spheres you see,
with almost a white color circle around it?
Well that's the chondrocyte, the reddish pink,
inside the space which is called lacuna.
Lacuna is that almost whitish color around it.
Think about taking a beach ball and putting a marble inside,
or something like that.
You have two spheres,
one large, lacuna,
one smaller, chondrocyte, inside of it.
Now, this cartilage is great
for having shock absorption.
It's great for helping to keep stability,
but allowing some flexibility.
Another specialized structure in connective tissue
is the bone.
Now, bone has this inorganic matrix
with tons of calcium cells.
Now, it's not just one type of calcium cell,
there are many types of calcium cells.
By mixing all these calcium cells together,
the bone can become very, very hard,
but you also have the fibers.
Plenty of collagen fiber
to help keep those cells together.
This is showing a slide of your bone.
What you're seeing here
kinda looks like a tree trunk, almost.
You see a big black circle in the center,
and then rings forming around it.
Those rings are filled with calcium.
The black dots that look like they have little
kind of hairs or roots coming off?
Those black dots are the cells.
The cells are embedded in the calcium.
The big black dot in the middle
is where you find the blood.
That's where all the blood and nerve grid are found.
So this is your bone.
A very specialized connective tissue.
Another specialized is blood.
Going from complete solid of bone
to complete liquid of blood.
It's your only tissue that is a liquid tissue.
The matrix is actually fluid,
it's the plasma of the blood.
It's the liquid in between the red blood cells
and the white blood cells,
and the platelets.
You're thinking hold on, we need to have fibers.
It still has fibers.
Blood still contains the fibers.
But look at the slide, where are the fibers?
You can see the platelets,
you can see a white blood cell,
you can see a red blood cell,
but where are the fibers?
All that whitish color is going to be matrix,
but I still don't see the fibers.
Willing to bet you've seen the fibers before.
Any idea where?
Well, I'm gonna take a guess here
that you've probably had a cut at some point in your life.
When that cut scabs over,
the scab is made up of many things,
but one of the main components
are the fibers from your blood.
They form this patch
that is going to cover and seal up the site.
Now, it's not just fibers,
you've got tons of platelets in there also.
But those are the fibers.
You've seen them.
Any scab is filled with fibers from the blood.
And we have adipose tissue.
Now, adipose tissue is kind of special because
the cell itself has very few organelles,
or very few central components.
The adipose tissue cell
is filled with adipose, or fat.
By filling cell upon cell with fat, or lipids,
it's helping to insulate your body.
It's helping to protect your body.
It's also great energy storage.
All right, well insulation, that makes sense,
fine, no problem.
Because if you have a layer of fat,
it's gonna slow down the heat from entering or exiting.
But protection?
Yeah, those fat cells act as a cushion.
Energy storage.
Your body can take the molecules stored
within these adipose cells
and break them down into usable energy for the cells.
So adipose does more than just insulate the body.
It's also protection and energy.
So here we go looking at an image of adipose.
The actual micrograph on the left,
all those roughly circular, oval shaped structures,
with the very thin lines,
those are going to be the adipose cells.
That one, almost in the middle of the picture,
has a very thick wall, little black dots?
That's gonna be a blood vessel,
we don't need to deal with that now.
So look at the very thin walls,
kinda that off-white, almost blueish tinge inside.
Those are your adipose cells.
You can see there's no nucleus in there.
You know, in reality, there is a nucleus.
The nuclei have pushed all the way off to the side.
So we have a nucleus, it's just pushed off to the side,
because the fat is filling the entire inside of the cell.