The lymphatic system helps maintain fluid balance, absorbs fats, and aids the immune system. It contains lymph vessels, lymph nodes, lymph, the spleen, thymus, and tonsils. Lymph nodes filter lymph and add infection-fighting lymphocytes. Together with nonspecific defenses like skin and inflammatory response, and specific defenses like antibodies and lymphocytes, the immune system protects the body from pathogens. Disorders can cause allergic reactions, immunodeficiencies, or autoimmune diseases where the immune system attacks the body's own tissues. The lymphatic system develops after birth as the baby gains its own active immunity.

1. Western Philippines University

2. What is Lymphatic System?
•The lymphatic system is a network of tissues and organs
that primarily consists of lymph vessels, lymph nodes
and lymph.
•Is part of the body’s defense system against
microorganisms and other harmful substances. In
addition, it help maintain fluid balance in tissues and to
absorbs fats from the digestive tract.

3. Lymph
•Lymph is the fluid that circulates throughout the lymphatic
system.
•Lymph returns proteins and excess interstitial fluid to the
bloodstream. Lymph may pick up bacteria and bring them
to lymph nodes where they are destroyed.
Harmful materials that enter lymph vessels:
• Bacteria
• Viruses
• Cancer cells
• Cell debris

4. 1. Lymph Vessels
Like arteries and veins, lymphatic vessels
sprawl in a connected system to collect the
lymph that leaks from the blood capillaries
and conduct it to the large veins of the
neck. The network functions to return
lymph to the general circulation.

5. 2. Lymph Nodes
They filter the lymph that passes through the vessels
and add lymphocytes to it.
- Lymphocytes are a type of white blood cell. There are
two types, small lymphocytes and large lymphocytes,
and they defend the host from disease and infection.

6. 3. Tonsils
A main function of tonsils is to trap germs
(bacteria and viruses) which you may breathe in.
Proteins called antibodies produced by the
immune cells in the tonsils help to kill germs and
help to prevent throat and lung infections.

7. 4. Thymus
The function of the thymus is to receive
immature T cells that are produced in the red
bone marrow and train them into functional,
mature T cells that attack only foreign cells.

8. 5. Spleen
The largest organ of the lymphatic system,
processes blood and removes dead or defective red
blood cells, and keeps a reserve of blood in case of
hemorrhaging. It also produces new red blood cells
in a developing fetus.
The spleen also serves as a site where lymphocyte
populations increase.
Did you know that you can live without a spleen? Your liver will take
over some of the spleen's work!

10. Body Defenses
The body is constantly in contact with bacteria, fungi,
and viruses.
The body has two defense systems for foreign materials:
•Nonspecific defense system
•Specific defense system

11. Nonspecificdefensesystem
•Mechanisms protect against a variety of invaders
•Responds immediately to protect body from foreign
materials
•Provided by body surface coverings
- intact skin, mucous membrane, cellular proteins and
inflammatory response.
•Specialized human cells
•Chemicals produced by the body as the immune system.
Body Defenses

12. Specificdefense system
•Known as the immune system
•Specific defense is required for each type of invader
Body Defenses

13. Body Defenses

14. 1st Line of Defense (Surface Membrane Barriers)
1. The skin
• Physical barrier to foreign materials
• pH of the skin is acidic to inhibit bacterial growth
• Sebum is toxic to bacteria
• Vaginal secretions are very acidic
2. Stomach mucosa
• Secretes hydrochloric acid
• Has protein-digesting enzymes
- Saliva and lacrimal fluid contain lysozyme
- Mucus traps microogranisms in digestive and respiratory
pathways

15. Defensive Cells
Phagocytes
(neutrophils and
macrophages)
• Engulfs foreign material into
a vacuole
• Enzymes from lysosomes
digest the material
Natural killer cells
• Can lyse and kill cancer cells
• Can destroy virus- infected
cells

16. 2nd Line of Defense (Inflammatory Response)
•Triggered when body tissues are injured
•Produces four cardinal signs
1. Redness
2. Heat
3. Swelling
4. Pain
•Results in a chain of events leading to protection and
healing
Inflammatory response

17. Functions of the Inflammatory Response
• Prevents spread of damaging agents
• Disposes of cell debris and pathogens
• Sets the stage for repair

18. The Inflammatory Response
•Begins with a chemical ‘alarm”- Histamines when
cells are injured
•Blood vessels dilate increases blood flow to area
causing redness and heat.
•Capillary beds become permeable becoming
leaky, which increases edema
•Pain receptors are activated
•Phagocytes and WBC are attracted to the area:
- Chemotaxis = cells follow chemical gradient

19. 3rd Line of Defense (The Immune System )
•Antigen specific – recognizes and acts against
particular foreign substances
•It stalks and eliminates any invading pathogen
•Systemic – not restricted to the initial infection site
•Has memory – recognizes and mounts a stronger
attack on previously encountered pathogens

20. 2 Types of Immunity
Humoral immunity
• Its Antibody-mediated immunity where antibodies are
present in the body’s fluids
• Cells produce chemicals for defense
Cellular immunity
• Cell-mediated immunity where lymphocytes themselves
defend the body.
• Cells are the protective factors that target virus infected
cells

21. Antigens
(Nonself = foreign intruders)
•Antigen = any substance capable of exciting the
immune system and provoking an immune response
•Examples of common antigens:
• foreign proteins, nucleic acids, large carbohydrates,
pollen grains, microorganisms
•As the immunity system develops, it inventories all
these proteins so it recognizes them as self.

22. Self - Antigens
• Human cells have many surface proteins
• Our immune cells do not attack our own proteins
• Our cells in another person’s body can trigger an
immune response because they are foreign
•Restricts donors for transplants

23. Passive Immunity
• Antibodies are obtained from someone else
- From a mother to her fetus
- Artificially from immune serum or gamma globulin
• Immunological memory does not occur.
• Protection provided by “borrowed antibodies” is
short-lived

24. Disorders of the Immunity
1. Allergies (Hypersensitivity)
Reaction with allergen
2. Immunodeficiencies
Production or function of immune cells or complement is abnormal
3. Autoimmune Diseases
The immune system does not distinguish between self and nonself
The body produces antibodies and sensitized T lymphocytes that attack its
own tissues

25. Developmental Aspects of the Lymphatic System
•Lymphoid organs are poorly developed before birth, except
the thymus & spleen
•A newborn has no functioning lymphocytes at birth; only
passive immunity from the mother
•If lymphatics are removed or lost, severe edema results, but
vessels grow back in time.