The Lymphatic and Immune Systems PG 161 LYMPHATIC

The Lymphatic and Immune Systems

PG. 161

LYMPHATIC SYSTEM Supplements the circulatory system Composed of: lymph, lymph nodes, lymph vessels, tonsils, spleen, thymus gland, lacteals, Peyer’s patches, and lymphoid tissue There is no muscular pump or heart Functions include: acting as intermediary between blood and tissue, transporting excess filtered tissue fluid, producing lymphocytes to destroy harmful bacteria, and absorb fat and fatsoluble vitamins

LYMPH/INTERSTITIAL FLUID Lymph formation begins when blood plasma leaks out of blood vessel capillaries, now called interstitial fluid (~4 liters per day). It is composed of water, lymphocytes, some granulocytes, digested nutrients, hormones, salts, carbon dioxide, and urea Some of this fluid enters lymph capillaries, now called lymph. Moves with assistance of skeletal tissue contraction, breathing movements, and valves

LYMPH VESSELS Accompany and closely parallel the veins—auxiliary to circulatory system Located in almost all of the tissue and organs that have blood vessels Interstitial fluid enters lymph vessels and they join to form larger lymph vessels called lymphatics Two large, main lymphatics: right lymphatic duct, left lymphatic duct (thoracic duct) Flows in only one direction, from the body organs to the heart

LYMPH NODES Small structures located alone or grouped in various places along the lymph vessels throughout the body Contain a slight depression on one side called the hilum where the efferent lymphatic vessels and a nodal vein leave the node and a nodal artery enters Covered by a capsule of fibrous connective tissue that extends into node called trabeculae Lymphatic vessels enter node at afferent lymphatic vessels Nodule surrounds a germinal center that produces the lymphocytes § When germinal centers are stimulated by microorganisms or foreign substances, the immune response is activated

LYMPH NODES

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TONSILS Masses of lymphatic tissue capable of producing lymphocytes and filtering out bacteria Form a protective ring around the back of the nose and upper throat Subdivided according to their location: § Palatine located on sides of soft palate § Adenoids located in upper part of throat § Lingual may be found at back of tongue Get smaller in size as a person gets older

SPLEEN Saclike mass of lymphatic tissue located near the upper left of the abdomen beneath the diaphragm Forms lymphocytes and monocytes Filters out bacteria Stores red blood cells for cases of excessive bleeding or vigorous exercise Also destroys and removes old or fragile red blood cells Forms erythrocytes in the embryo

THYMUS GLAND Located in the upper anterior part of the thorax, above the heart Produces and matures lymphocytes called T lymphocytes It is also an endocrine gland that secretes a hormone called thymosin

PEYER’S PATCHES Found in the walls of the small intestines Produce macrophages Macrophages destroy bacteria and prevent bacteria from penetrating the walls of the small intestines

LACTEALS Specialized lymph capillaries found in villi of the small intestine Absorb digested fat and fat-soluble vitamins

EFFECTS OF AGING Decline in immune function Increased risk of infection Decreased ability to fight disease Slowed wound healing

DISORDERS OF THE LYMPH SYSTEM Lymphadema: swelling of tissues due to abnormal collection of lymph Lymphoma: tumor or lymphatic tissue Hodgkin’s disease: presence of large cancerous lymphocytes known as Reed-Sternberg cells Infectious mononucleosis: disease caused by Epstein-Barr virus; known as the “kissing disease” or “mono”

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FUNCTION OF IMMUNE SYSTEM Protect body from harmful substances – – Pathogens (disease-producing microorganisms) Allergens Toxins Malignant cells Immunity is the body’s ability to resist infections from pathogens, foreign substances, and toxic chemicals Humoral immunity (B lymphocytes) and cellular immunity (T lymphocytes) derive from the body’s lymphoid tissue Individuals differ in their ability to resist infection

NORMAL DEFENSE MECHANISMS The individual’s immune system serves as the normal defense mechanism against the transmission of infectious agents Ability to recognize foreign agent (antigen) Antibodies protect body against antigens Specific and nonspecific immune defenses

ANTIGEN-ANTIBODY REACTION Also known as immune reaction Binds antigens to antibodies Antibody is a disease-fighting protein

NONSPECIFIC IMMUNE DEFENSE Protects from all microorganisms Not dependent on prior exposure to antigens Includes: – – – Skin and normal flora Mucous membranes Sneezing, coughing, and tearing reflexes Elimination and acidic environment Inflammation Immunoglobulins

SPECIFIC IMMUNE DEFENSE Lymphocytes are precursors of many cells involved in immune response: – – – – B cells Plasma cells Helper T cells Killer T cells Suppressor T cells Memory cells Macrophages

CHEMICALS AND IMMUNE RESPONSE • Lymphokines stimulate monocyte and macrophage activity • Activated macrophages release monokines – Interleukin-1 stimulates T-cell proliferation and causes fever – TNF kills tumor cells; attracts agranular leukocytes – Complements cause breakdown (lysis) of microorganisms and enhances inflammatory process

NATURAL AND ACQUIRED IMMUNITIES Natural immunity – Immunity we are born with – Inherited and permanent – Anatomical barriers and cellular secretions Acquired immunity – Reaction that occurs as a result of exposure to invaders – Developed during an individual’s lifetime – May be passive or active § Passive acquired immunity – Acquired artificially by injecting antibodies from blood of other individuals § Active acquired immunity – Natural acquired immunity results from having had and recovered from a disease – Artificial acquired immunity comes from being inoculated with a suitable vaccine, antigen, or toxoid (e. g. , immunizations)

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IMMUNIZATION Process of increasing an individual’s resistance to an infection by artificial means Immunization charts – Ages 0 -6, 7 -18, Adult, Catch-up

AUTOIMMUNITY Autoimmune disorder: when the body mistakenly targets the normal cells, tissues, and organs of a person’s own body Triggered by multiple causes Examples include: § § § § § Addison’s disease Hypothyroidism/hyperthyroidism Lupus Multiple sclerosis Myasthenia gravis Pernicious anemia Psoriasis Scleroderma Type I diabetes mellitus Ulcerative colitis/Crohn’s disease

HYPERSENSITIVITY When the body’s immune system fails to protect itself against foreign material Caused by allergens (antigens that causes allergic responses) Severe and sometimes fatal allergic reaction is called anaphylaxis or anaphylactic shock People with allergies should wear medic-alert tags in the event of an emergency

HIV/AIDS Human immunodeficiency virus (HIV) causes AIDS § Progressively destroys body’s T 4 -lymphocyte cells, the immune systems key infection fighters § Three outcomes can result from infection with HIV: development of AIDS, development of condition known as AIDS-related complex (ARC), and asymptomatic infection A – Acquired – The disease is not inherited I – Immune – Refers to the body’s natural defenses against cancers, disease, and infections D – Deficiency – Lacks cellular immunity S – Syndrome – Set of conditions that are present to signal a diagnosis

TRANSMISSION OF HIV/AIDS Sexual contact Sharing hypodermic needles From infected mother to baby: in utero, at birth, or through breast feeding Transfusion of contaminated blood, semen donations, skin grafts/organ transplants from infected person **No evidence that HIV is spread through sweat, tears, urine, or feces. The virus is fragile and does not survive outside the body**

PREVENTING TRANSMISSION OF HIV/AIDS Education and training Limit sexual contacts Use of condoms Do not share needles Clean up soiled materials Cover wounds Tell partner if you have HIV/AIDS Standard precautions used by all health care professionals