00:01
Now we'll talk about the white
blood cells, these are our leukocytes.
00:04
These are nucleated
independently modal structures.
00:07
They are highly differentiated and
these are our cells of the immune system.
00:11
They compose the body's defense mechanisms.
00:14
They're generated in the bone marrow and normal
values range between 4,000 and 11,000 (cells/mm3).
00:21
Leukopenia is a term we use to
describe a low white blood cell count.
00:25
And leukocytosis describes
a high white blood cell count.
00:29
There are three types: we have the granulocytes, the
lymphocytes and the monocytes. We'll touch on each.
00:35
First the granulocytes.
These are the most numerous.
00:39
The nucleus is gonna contain granules
and this is where they get their name,
and these are the mediators
of our inflammatory response.
00:46
Basophils are the least common of these
granulocytes and they can perform phagocytosis.
00:51
They can produce histamine and serotonin and these
cells play a role in immune regulation and allergic responses.
00:58
Next we see eosinophils and these make
up about 1 to 4% of the white blood cells
and these play a role in the
defense against parasitic infections.
01:07
These will increase called eosinophilia in the setting
of parasites, asthma and certain tropical diseases.
01:15
So you can remember, "worms, wheezes and weird
diseases" - we will see elevated eosinophils.
01:22
Our third is neutrophils and these can perform
phagocytosis and are the most abundant type of granulocyte.
01:29
Now we'll cover the lymphocytes.
01:31
These are the immune response
to a foreign substance in the body.
01:35
These are found in the lymph nodes, the spleen, the thymus,
the tonsils and the lymphoid tissue of the GI tract.
01:42
They're going to enter the circulation
freely through the thoracic lymph duct.
01:46
These can live a long time, up to 1 year.
01:49
These are part of the acquired or smart
immune system, they have a memory.
01:55
There are three types,
first the natural killer cells.
01:58
These are going to distinguish infected
cells and tumors from normal uninfected cells
by recognizing changes in a
surface molecule called the MHC.
02:07
These become activated and release cytotoxic or cell-killing
granules and then they destroy these altered cells.
02:15
Next are the B cells.
02:16
These are part of the humoral immunity and they're
responsible for making large quantities of antibodies
which can neutralize foreign
objects like bacteria and viruses.
02:26
Last are the T-cells.
02:28
These are part of the cell-mediated immune response
and these are going to directly attack antigens.
02:33
Lymphocytes are expressed as a percentage of the lymphocytes
compared to the total number of white blood cells counted.
02:40
Lymphocytosis refers to an increased number, and
usually this happens in the setting of a viral infection
or in certain kinds of
blood cancers or lymphoma.
02:50
Lymphocytopenia refers to a decreased
number, and we see this in patients with HIV
because this will destroy their T-cells.
02:59
Next, the monocytes.
03:00
Monocytes are the largest cells of the blood,
they compose about 7% of the leukocytes.
03:06
They're phagocytic which means they
ingest infectious agents and red blood cells.
03:11
They're found at the sites of chronic infection
and these are made in the bone marrow
and then they're gonna
circulate around in the blood.
03:18
These are young and they're going to
eventually develop into macrophages.
03:22
Here you see the timeline.
03:23
When they come out, they're just a
monoblast, then they mature into a promonocyte
into a monocyte which will further
differentiate into a macrophage.
03:34
Next are the platelets.
03:35
These do not reproduce, these are
small fragments of bone marrow cells.
03:40
Normal values range from about 150,000
to 400,000 and these are used for clotting.
03:46
They also are used to promote other clotting factors in
the clotting cascades and these secrete vasoconstrictors.
03:55
Platelets attract neutrophils and
monocytes to a site of inflammation.
03:59
They're also responsible for dissolving clots when they're
no longer needed and they can digest and destroy bacteria.
04:06
They're also going to secrete growth
factors to maintain the lining of the vessels.