- [Instructor] So, ligaments and tendons are types
of extra strong and dense connective tissues.
Ligaments connect bones to other bones,
and tendons connect muscle to bone.
And the point where one bone articulates
or meets up with another is called a joint.
Now, there are different types
of joints found throughout the body,
and the first type is called synarthroses,
which are immovable joints
where two bones are fused together.
For example, you'll find these types of joints in the skull.
When you were a baby, your skull was made up of a bunch
of different pieces that grew as your brain grew.
And then, as an adult,
the joints between these bones then fused
and became synarthroses.
The next type of joint is called an amphiarthroses.
Amphi- meaning it's both stiff but also slightly movable.
And an example of amphiarthroses
would be your vertebral joints.
And then finally, we have what are synovial joints,
which are also known as diarthroses,
of which there are a couple different types.
One type, for example,
is the ball and socket synovial joint,
and you'll find examples of ball and socket joints
in your shoulders or in your hips.
These are joints that have many degrees of motion.
And then, another type of synovial joint is the hinge joint.
An example of a hinge joint would be,
say, your elbow or your knee
where that joint pretty much moves in just one plane,
like the hinge of a door.
Now, synovial joints are named so
because they are lubricated
by a fluid called synovial fluid,
which is contained within the synovial capsule
that surrounds the whole joint.
Now, the surfaces of bones that meet up in a joint
are lined by a special kind of smooth cartilage
called articular cartilage,
which is composed of specifically hyaline cartilage.
And articular cartilage, like all cartilage, is avascular,
meaning it lacks any sort of vasculature or blood vessels.
And so, it has a hard time getting the nutrients it needs
to heal and recover if it were to become damaged
by overuse or infection.
And as you might be somewhat familiar with,
the overuse of joints over time can lead to inflammation,
which is called arthritis,
from arth- meaning joint,
and -itis meaning inflammation.
And this can lead to permanent destruction
of articular cartilage,
which causes the pain and stiffness of arthritis.