Lymphatic system and body defense By: Audrey McNicholl and Megan Saunders

Functions of the Lymphatic System The lymphatic system returns excess interstitial fluid to the blood, absorbs fats and fat- soluble vitamins, and provides defense against disease

Components Lymph is the fluid in the lymphatic vessels. It is picked up from the interstitial fluid and returned to the blood plasma Lymphatic vessels carry fluid away from the tissues The right lymphatic duct drains lymph from the upper right quadrant of the body. The thoracic duct drains all the rest Lymph enters a lymph node through afferent vessels, filters through the sinuses, and leaves through an efferent vessel

Components

Components cont. Lymph nodes filter and cleanse the lymph before it enters the blood Tonsils are clusters of lymphatic tissue associated with openings into the pharynx and provide protection against pathogens that may enter through the nose and mouth When the tonsils become enlarged they may interfere with breathing and are called adenoids The spleen is a lymph organ that filters blood and also acts as a reservoir for blood

Resistance to Disease The ability to counteract pathogens is resistance Susceptibility is a lack of resistance Barriers that deter microbial invasion may be mechanical (skin), fluid (tears), or chemical (lysozymes) Interferon has particular significance because it offers protection against viruses Interferon is produced by virus-infected cells to provide protection for the neighboring cells

Resistance to disease cont. Inflammation is a nonspecific body defense mechanism that occurs in response to tissue damage from microorganisms or trauma Localized inflammation is contained in a specific region Inflammation sets the stage for tissue repair and usually happens when tissues are damaged

Steps in inflammation

Specific Defense Mechanisms Specific defense mechanism provide the third line of defense against microbial invasion. This third line defense is specific resistance, or immunity Specificity and memory are two characteristics of specific defense mechanisms. The two primary cells that are involved and lymphocytes and macrophages A molecule that is interpreted as nonself and that triggers an immune response is called a foreign antigen Antigens are molecules that trigger an immune response

Development of lymphocytes Like all other blood cells, lymphocytes develop from stem cells in the bone marrow During fetal development, the bone marrow releases immature and undifferentiated lymphocytes into the blood, some go on to become T cells and some B cells T cells are responsible for cell mediated immunity in which the T cells directly attack the invading antigens B cells are responsible for anti-body mediated immunity

Devp. Of lymphocytes

Acquired Immunity 4 different kinds of ways to acquire specific resistance, or immunity The terms active and passive refer to whose immune system reacts to the antigen Active immunity occurs when the individual’s own body produces memory T cells and B cells in response to a harmful antigen Active immunity takes several days to develop but lasts a long time Passive immunity results when the immune agents develop in another person and are transferred to an individual who was not previously immune Passive immunity is immediately effective but does not last long

Acquire immunity cont. The terms natural and artificial refer to how the immunity is obtained Natural immunity is acquired through normal activities Artificial immunity requires some deliberate action

Chapter Recall Lymph Capillaries Collects lymph from three-fourths of the body Enlarged Pharyngeal tonsils Lack of resistance Provides localized protection against viruses Cause an increase in body temperature Principal cell involved in cell-mediated immunity Protein that triggers an immune response Produce antibodies Rapid, intense reaction against an antigen Adenoids Antigen Interferon Lacteal Plasma cells Pyrogens Secondary response Susceptibility T cells Thoracic duct

Answers Lymph Capillaries D-Lacteal Collects lymph from three-fourths of the body J-Thoracic Acid Enlarged Pharyngeal tonsils A-Adenoids Lack of resistance H-Susceptibility Provides localized protection against viruses C-Interferon Cause an increase in body temperature F-Pyrogens Principal cell involved in cell-mediated immunity I-T cells Protein that triggers an immune response B-Antigen Produce antibodies E-Plasma Cells Rapid, intense reaction against an antigen G-Secondary Response