LYMPHATIC SYSTEMBy Ian Paris and Ashley Lawson

Role of the Lymphatic System

• Three main purposes provided by system:

1. Fluid and protein balance: Collects fluid and returns it to circulatory system

2. Immunity and spread of infection: It is the first line of defense again disease

3. Digestion: Absorbs fat from food in digestion(2)

Function of Lymphatic Vessels

Main function is to aid in fluid balance.

Lymphatic Vessels keep left over interstitial fluid from building up

The vessels act as drains that collect the excess fluid and return it and lymph to the blood just before it reaches the heart through a lymphatic pump.

If left over fluid is left for even a short amount of time the result can be massive edema or swelling resulting in tissue destruction or death.(2)

The vessels also help with homeostasis

They remove large molecular substances that can’t be absorbed by blood capillaries and return accumulated protein back to blood.

Lymphatic Vessels in the small intestine called lacteals absorb fats and other nutrients(1)

Lymph Nodes

Function of Lymph Nodes: Provides defense against harmful forces

by filtration and phagocytosis Sinus channels in lymph nodes slow

lymph flow giving cells time to remove microorganisms and other damaging particles from lymph.(1)

Tonsils Tonsils are masses of

lymphoid tissue located in a protective ring under mucous membranes in mouth and back of throat.

Function of tonsils: Help protect against bacteria invading tissue in area around openings between oral and nasal cavities.

Serves as first line of defense from exterior infection and disease.

Main job is to keep pathogens from ever getting into our body through our mouth or nose. (1)

Thymus

Thymus is an unpaired organ consisting of two pyramid-shaped lobes.

Function of Thymus: Is final site of lymphocyte development before birth.

Soon after birth the thymus starts secreting a group of hormones called thymosin that enable lymphocytes to develop into mature T-cells.

T-cells are just lymphocyte cells produced by thymus gland that participate in immune response.(3)

Spleen

The spleen is located under the diaphragm

Functions of Spleen: Defense: macrophages

remove microorganisms from blood and destroy them through phagocytosis.

Hematopoiesis: monocytes and lymphocytes complete development and become active in spleen

Before birth red blood cells are developed in spleen.

Red blood cell and platelet destruction: macrophages remove worn-out red blood cells and defective platelets from blood and destroy them through phagocytosis.

Iron and globin are taken from destroyed red blood cells and returned to blood stream for storage in bone marrow and liver.

Blood Reservoir: Blood is stored in pulp of spleen in case of hemorrhage.

General vs. Specific Immunity

• General: It doesn’t attack anything specific

• Example: skin blocks everything that is trying to enter the body.

• Response: If bacteria does enter the body then damaged cells signal for increased blood flow. This increases body temperature that creates an unfavorable environment and delivers T-cells which are supposed to get rid of damaged cells and dead bacteria. (1)

• Specific: Attacks specific types of infections

• Example: Vaccination that forms antibodies that create an immunity to the infection.

• Response: Antibodies are created and delivered to infected areas to destroy a specific type of infection.(1)

Active vs. Passive Immunity

Active: A person develops a disease and acquires an immunity to it.(ex. measles as a child)

Injection of a contributing agent results in immunity. (ex. vaccination for polio)

Passive: Baby receives protection from mother through placenta in womb or an infant receives protection from disease causing agents from mother’s milk.

Injection of antibodies that were developed by someone else's immune system.

Sources

1. http://www.cayuga-cc.edu/people/web_pages/greer/biol204/lymphatic1/lymphatic1.htm

2. http://www.lymphaticresearch.org/main.php?menu=about&content=lymphsys

3. http://www.google.com/#hl=en&biw=1260&bih=574&q=T+cell&tbs=dfn:1&tbo=u&sa=X&ei=5ovMTayyCs_ogQeGz_DgBA&ved=0CCQQkQ4&bav=on.2,or.r_gc.r_pw.&fp=9de76c24b15c82b4