The lymphatic system removes excess fluid from tissues and returns it to the bloodstream. Lymph, the fluid collected in lymphatic vessels, contains lymphocytes that help the body fight disease. The lymph passes through lymph nodes which filter out pathogens and foreign materials, and swells when fighting infection. Important lymphatic organs include the tonsils, thymus, and spleen, which all help the immune system by filtering pathogens from the blood or lymph and producing lymphocytes. HIV attacks lymphocytes and weakens the immune system, leaving the body vulnerable to opportunistic infections.

1. Lymphatic System
Section 3.3

2. Lymphatic system
When you turn on a faucet the
excess water runs down the drain.
Your body’s excess tissue fluid is removed
by the lymphatic system.

3. Lymphatic system
Nutrients, water and oxygen molecules in the
blood diffuse through capillary walls to nearby
cells.

4. Lymphatic system
Those substances can become part of the tissue
fluid that is found between cells.

5. Lymphatic system
This fluid is collected and returned to the blood
by the lymphatic system.

7. Lymphatic system
Once the fluid is in the lymphatic
capillaries, it is called lymph.

9. The Lymphatic System
carries lymph
through a network of
lymph capillaries and
larger lymph vessels.
Then lymph drains
into large veins near
the heart.
Lymphatic Circulation

10. There is no pump, like
the heart, in the
lymphatic system.
The movement of
lymph depends on the
contraction of smooth
muscles in the lymph
vessels and skeletal
muscles.

11. Lymph vessels, like
veins, have valves that
keep lymph from
flowing backwards.
If the lymphatic system
is not working
properly, severe
swelling occurs because
the tissue fluid cannot
get back to the blood.

12. Lymph contains water and dissolved substances,
but it also contains lymphocytes.
Lymphocytes are a type of white blood
cell that help your body defend against disease-
causing organisms.

13. Lymphatic Organs
Before the lymph enters the blood, it passes
through lymph nodes, which are
bean shaped organs of varying sizes found
throughout the body.
Lymph nodes filter out microorganisms and
foreign material that have been taken up by
lymphocytes.

15. Lymphatic Organs
When your body fights an infection,
lymphocytes fill the lymph nodes.
The lymph nodes become swollen, warm,
reddened, and tender to the touch. After the
invaders are destroyed, the swelling,
redness, warmth and tenderness in the
lymph nodes goes away.

20. Lymphatic Organs

21. Lymphatic Organs
Another important lymphatic organ is the
tonsils.
They are in the back of your throat and
protect you from harmful microorganisms
that enter through your mouth and nose.

23. Lymphatic Organs
Another important lymphatic organ is the
thymus.
The thymus is a soft mass of tissue located
behind the sternum.
It makes lymphocytes that travel to other
lymph organs.

25. Lymphatic Organs
Another important lymphatic organ is the
spleen.
This is the largest lymphatic organ.
It is located behind the upper-left part of the
stomach and filters the blood by removing
worn out and damaged red blood cells.
Cells in the spleen take up and destroy
bacteria and other harmful substances.

27. Disease of the Lymphatic System
HIV is a deadly virus.
When it enters a person’s body, it attacks
and destroys lymphocytes, called helper T
cells that help make antibodies to fight
infections.
This affects the person’s immunity against
certain diseases.
Usually the person dies of one of those
diseases, not from the HIV virus.