00:01
So if we take a closer look
into the structure of our arteries,
we find that they're divided into
three different types.
00:10
We have the elastic arteries,
which are going to have
a large amount of elastin
in their walls.
00:17
The muscular arteries,
which are going to have
a larger amount of smooth muscle
in their walls.
00:22
And then we have the
smaller arterioles.
00:26
Starting with the elastic arteries,
these are going to be thick walled
with large low-resistance lumens.
00:34
Examples include the aorta
and its major branches.
00:39
It is also called
conducting arteries
because elastic arteries are going
to conduct blood from the heart
to the medium size vessels.
00:49
Elastin is going to be found
in all three tunics
of the elastic arteries,
but most of the elastin
is going to be found
in that middle layer
or the tunica media.
01:03
This is going to contain a
substantial amount of smooth muscle,
but this smooth muscle
is actually inactive
during vasoconstriction.
01:14
The elastic fibers act as
pressure reservoirs
that expand and recoil as blood
is ejected from the heart,
which allows for continuous
blood flow downstream
even between heartbeats.
01:31
Next, we have
the muscular arteries.
01:34
Elastic arteries
are going to give rise
to this second type of artery.
01:40
These are sometimes also called
distributing arteries
because they deliver blood
to the body organs.
01:48
The diameters of our
muscular arteries
are going to range in size
from the size of your pinky finger
to a very small size
like the size of pencil lead.
02:00
They can account for most of the
named arteries in our bodies.
02:06
Muscular arteries have the
thickest tunica media,
but this tunica media is going to
have more smooth muscles
than it does elastic tissue.
02:17
The tunica media is usually
sandwiched between
an elastic membrane.
02:22
And it is very active in
vasoconstriction.
02:28
The last type of artery and
the smallest of our arteries
are going to be
our arterioles.
02:34
Our larger arterioles contain
all three tunics,
but as they get smaller
in size and diameter,
they end up being mostly a
single layer of smooth muscle
surrounding endothelial cells.
02:50
The arterioles are going to
control flow of blood
into our capillary beds
via vasodilation
and vasoconstriction
of their smooth muscle.
03:02
Because of this they are also
sometimes called resistance arteries
because they change diameters
in order to change the
resistance to blood flow.
03:12
Arterioles lead into
our capillary beds.