Lymphatic & Immune Systems

Health SciencesD. Young

Functions of the Lymphatic System

Return cellular waste products and excess fluid from the tissues to the circulatory system.Absorb fats and fat-soluble vitamins from the digestive system and transport them to the cells.Serve as an important part of the immune system.

StructuresLymph fluid Intercellular fluid/interstitial fluid

Plasma that flows out of the capillaries of the circulatory system into the spaces between the cells.

Carries food, oxygen and hormones to the cells Lymph fluid

Returns intercellular fluid containing waste products from the cells to the venous circulatory system. Also returns any blood cells that escaped from the capillaries.

Structures Cont’dLymph Vessels Lymph capillaries – thin-walled tubes that carry

lymph fluid from the tissues to the larger lymphatic vessels

Right lymphatic duct & the thoracic duct empty lymph into the veins in the upper thoracic region.

Lacteals – specialized lymph capillaries located in the villi of the small intestine. Fats & fat-soluble vitamins are absorbed and carried into the bloodstream.

Structures Cont’dLymph NodesSmall bean-shaped structures located in

lymph vessels that provide a site for lymphocyte production.

Filter lymph to remove harmful substances such as bacteria, viruses & malignant cells as lymph flows through the node.

Swollen lymph nodes are often a sign of a disease process.

Structures cont’dTonsilsMasses of lymphatic tissue that form a

protective rign around the nose and upper throat.

Adenoids – nasopharyngeal Tonsils – located behind the nasopharnx

Palentine tonsils – located in the portion of the throat that is visible through the mouth

Lingual tonsils – located at the base of the tongue.

Structures cont’dVermiform AppendixLymphatic tissue that hangs from the lower

portion of the cecum of the large intestine.Peyer’s patches – are small areas of

lymphatic tissue located on the walls of the large intestine

                                                                                                                                         

                 

Structures cont’dSpleen Saclike mass of lymphatic tissue located in the left

upper quadrant of the abdomen, just below the diaphram & behind the stomach.

Filters microorganisms & other foreign material from the blood

Forms lymphocytes & monocytes which are specialized WBC’s with roles in the immune system.

Is hemolytic – removes and destroys worn-out red blood cells.

Stores extra erythrocytes and maintains the appropriate balance between the red blood cells and plasma in the circulation.

Functions of the Immune System

Protect the body from harmful substances including pathogens, allergens, toxins and malignant cells.

StructuresNot contained within one body system.Depends on structures from several other body systems.

First Lines of DefenseTo keep foreign substances from entering the body Intact skin – wraps the body in a physical barrier

that prevents invading organisms from entering the body

Respiratory system – traps breathed in substances with the nose hairs and the moist mucous membranes that line the respiratory systems. Coughing & sneezing help expel foreign matter from the respiratory system.

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Defense Cont’dDigestive SystemUses acids and enzymes produced by the

stomach to destroy invaders that are swallowed or consumed with food.

Lymphatic SystemEssential in fighting invaders once they

have entered the body.

Immune ResponseAntigen-antibody reaction Antigen

Any substance such as a virus, bacterium, or toxin that the body regards as foreign. Antigens stimulate the immune response.

Antibody Disease-fighting protein created by the immune system in

response to the presence of of that specific antigen. Immune reaction

Involves binding these foreign antigens to antibodies to form antigen-antibody complexes. This tags the potentially dangerous antigen so that it can be recognized and destroyed.

Specialized CellsLymphocytesSpecialized cells formed in bone marrow

and undergo further maturation & differentiation in lymphatic tissue throughout the body including the lymph nodes, spleen, thymus, tonsils and Peyer’s patches.

The two major classes of lymphocytes are B cells and T cells.

Specialized Cells cont’dB Cells Each B cell is designed to make only one specific antibody

against a specific antigen. Most effective against viruses and bacteria that are

circulating in the blood. Transformed into plasma cells when confronted with the

antigen. Enables the body to destroy the antigen in the antigen-antibody response.

Complement – complex series of proteins that circulate in normal serum. Activated on contact with an antigen & aid the antibodies by puncturing the cell membrane of the antigen.

Immunoglobulin (Ig) – synonym for the term antibody. There are five classes of immunoglobulins.

Specialized Cells cont’dT cellsAlso known as T lymphocytesSmall circulating lymphocytes that have

traveled to the thymus where they mature as a result of their exposure to thymosin.

Primary function is to coordinate immune defenses and to kill invading organisms on contact.

Specialized cells cont’dInterferonProduced by T cells.A family of proteins released when invaded

by a virus. Causes noninfected cells to form an

antiviral protein that slows or stops viral multiplication.

Specialized cells cont’dLymphokinesProduced by T cellsDirect the immune response by signaling

between the cells of the immune system. Attract macrophages to the infected site

and prepare them for attack

Specialized cells cont’dMacrophage Type of phagocyte Protects the body by ingesting invading cells and

by interacting with the other cells of the immune system.

Phagocyte A WBC with the ability to ingest and destroy

substances such as cell debris, dust, pollen, and pathogens. Known as phagocytosis.

ImmunityThe state of being resistant or not susceptible to a specific disease. Natural immunity

Passed from mother to fetus before birth. Also passed from mother to infant in breast milk.

Acquired immunity Acquired by development of antibodies during an attack

of an infectious disease. As an example, after having chickenpox antibodies are present against it.

Artificial immunity Immunization – immunity acquired through vaccination.

Immune Response FactorsHealthAgeHeredityOpportunistic Infection