00:00
Welcome.
00:01
In this lecture
we will be learning
about the lymphatic system
of the body.
00:08
The lymphatic system
is going to serve
to return fluids that have leaked
from our blood vessels
back to our blood.
00:17
The lymphatic system consists of
three main parts.
00:21
You have a network of
lymphatic vessels referred to
as the lymphatics.
00:26
The fluid inside those vessels
referred to as the lymph.
00:30
And finally we have the lymph nodes,
which are going to serve
to clean that fluid.
00:38
The lymphatic system is going to
return interstitial fluid
and leaked plasma proteins
back to the blood.
00:46
Recall that interstitial fluid
is that extracellular fluid
formed when components
of our blood plasma
leak out of our blood capillaries.
00:57
and then while some of that
blood plasma is reabsorbed,
the rest of it is going to drain
into the lymphatic vessels.
01:08
The lymphatic vessels
themselves
are an elaborate network
of drainage vessels.
01:15
They circulate about three liters of
interstitial fluid in a day.
01:21
And once the interstitial fluid
enters the lymphatics,
we then refer to that fluid
as the lymph.
01:30
Our lymphatic vessels
are going to offer
a one way system,
ensuring that the lymph
is going to flow
in only one direction
and that is toward the heart.
01:41
The lymph vessels
also referred to as lymphatics
include lymphatic capillaries,
as well as
larger lymphatic vessels.
01:52
These blind ended vessels
are going to weave
between the tissue cells
and our blood capillaries.
02:00
They are absent however,
from our bones,
teeth, bone marrow
as well as the
central nervous system.
02:07
Recall the
central nervous system
uses the cerebral spinal fluid
for drainage
instead of this
lymphatic system.
02:16
The lymphatic capillaries
are very similar
to our blood capillaries,
however, they are
a bit more permeable.
02:25
Unlike our blood capillaries,
the lymphatic capillaries
can take up
larger molecules and particles
that the blood capillaries
cannot.
02:34
So for example,
our lymphatic vessels
are able to bring in
proteins,
cell debris,
pathogens,
and even cancer cells.
02:44
And sometimes,
the lymphatic vessels, or
these lymphatic capillaries
can act as a route for these
pathogens or cancer cells
to travel throughout the body.
02:58
So depicted here,
you can see the
very intimate association
between our lymph capillaries,
which are in green,
and the blood capillaries.
03:12
Increased permeability of these
lymphatic capillaries
are due to multiple
specialized structures
two of those include the fact
that endothelial cells overlap
very loosely
to form one way valves.
03:28
So just like in the veins,
we have valves
we also have valves
in these vessels.
03:35
The many valves are going to be
anchored by
collagen filaments
to the matrix.
03:40
So it's going to increase
the extracellular fluid volume
as these many valves open
even more.
03:49
The decrease in the
extracellular fluid will cause
many valves to then close.
03:54
Also, in our GI tract
in the digestive system,
we have a specialized lymph
called Lacteal.
04:03
These lymph capillaries are going to
absorb digested fats
and deliver fatty lymph
or chyle to the blood.
04:14
The lymph capillaries
are going to drain into
increasingly large vessels.
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These vessels are called
collecting lymphatic vessels.
04:24
These vessels consist of:
collecting vessels,
trunks,
and ducts.
04:31
These vessels also have
structures and tunics
that are very similar
to that of veins.
04:37
Except that these are going to have
much thinner walls and more valves.
04:43
Also, these are going to anastomose
more frequently.
04:49
The collecting vessels in our skin
are going to travel
with our superficial veins,
while the deeper vessels will
usually travel with the arteries.
05:00
So these larger vessels,
also known as lymphatic trunks,
are formed by the union of the
largest collecting vessels,
and they're going to drain
large areas of the body.
05:14
The lymphatic trunks are named
for the part of the body
that they drain.
05:19
And they include
the paired lumbar
which are going to drain the lymph
from our lower limbs,
walls of the viscera
of the pelvis,
the kidneys,
the adrenal gland,
and the abdominal wall.
05:33
The paired bronchomediastinal
which are going
to drain the lymph
from the thoracic wall,
the lungs, and the heart.
05:42
The paired sabclavian
which are going to drain lymph
from the upper limbs.
05:47
The paired jugular trunks
which are going to join lymph
from the head and the neck.
05:52
And finally,
the single intestinal trunk
which is going to drain lymph
from our stomach,
intestines, pancreas, spleen,
and parts of the liver.
06:04
The lymph is then going to
be delivered from these trunks
into one of the two
large lymphatic ducts.
06:12
We have the
right lymphatic duct,
which is going to drain
the right upper arm
and the right side
of the head and the thorax.
06:21
Then we have the
thoracic duct,
which drains the entire
rest of the body.
06:27
In some individuals,
we also have this enlarged sac
in the abdominal area
known as Cysterna chyli.
06:36
This is where the thoracic duct
is going to actually start.
06:41
Each of these ducts
are going to empty the lymph
into our venous circulation
at the junction of the
internal jugular,
and subclavian veins
on each side of the body.