Lymphatic System Tissues, organs, vessels and a fluid called lymph similar to interstitial fluid Diffuse lymphatic tissue Tonsils, mucosa associated lymph tissue and red bone marrow Organs involved thymus spleen lymph nodes

Functions of the Lymphatic System Draining excess interstitial fluid & plasma proteins from tissue spaces Transport of some nutrients and hormones Immunity –specific defense recognize microbes or abnormal cells & respond by killing them directly or secreting antibodies that cause their destruction

Formation & Flow of Lymph Fluid & proteins filtered from blood capillaries are collected by lymphatic capillaries & returned to the blood Muscle contraction and breathing promote flow of lymph Lymphatic vessels empty into veins in shoulders

Lymph Circulation Lymphatic capillaries Capillaries are closed-ended tubes in tissues One-way valves Pickup fluid (lymph) from Tissues

Lymph Circulation LymphaticVessels Lymphatic Trunks Lymph passes from capillaries into lymph vessels Resemble veins with thin walls & valves Afferrent lymphatics carry lymph to nodes Efferent lymphatics carry lymph from nodes Lymphatic Trunks Lymph passes from lymphatic vessels into trunks *Bronchomediastinal, jugular, subclavian, intestinal and lumbar trunks

Lymph Circulation Lymphatic ducts Two ducts drain lymph from lymphatic trunks into the subclavian veins Thoracic Duct: Larger one that drains most of body lymph into the left subclavian vein Right Lymphatic Duct: Smaller one that drains right side of head, right shoulder and right arm into the right subclavian vein

Lymph Circulation Right Lymphatic Duct------ --------------------Thoracic Duct Right Lymphatic Duct------ Thoracic Duct----------------------------

Lymphatic Pathways Interstitial fluid  Lymph Capillaries  Afferent Lymphatic vessels  Lymph Nodes Efferent Lymphatic vessels  Lymphatic Trunks Lymphatic Ducts  Subclavian Veins

Lymphocytes B-cell lymphocytes T-cell lymphocytes Respond to antigens by dividing to produce Plasma cells: Antibody secreting cells Memory B-cells T-cell lymphocytes Cytotoxic T-cells that kill antigen-bearing cells Helper T-cells that help activate other T-cells and B-cells Memory T-cells Natural killer (NK) lymphocytes can kill invading cells and tumor cells without need to respond to antigens – nonspecific defense

Diffuse Lymphatic Tissues Lymphatic nodules – MALT (Mucosa Associated Lymph Tissues) lymphatic nodules within the digestive and respiratory systems Small intestine -Peyer's patches Appendix Bronchi of respiratory tract

Diffuse Lymphatic Tissues Tonsils Located in and around throat Tonsilar crypts Functions Crypts Trap microbes Mount immune response against inhaled and ingested microbes

Lymph organs Lymph nodes Structure Location Functions Throughout body but concentrated in groin, neck, armpit Functions Filter Lymph Mount immune response

Lymph Node Distribution

Lymph Organs Thymus Located in mediastinum above heart Large in infants atrophying with age Function Thymosin hormones for T-cell maturation

Spleen Located in upper left quadrant to left of stomach Functions Filters blood Produces lymphocytes Stores iron and platelets

Defense Non-specific Defense First Line Defense: External Skin Mucous Membranes Tears Saliva Stomach acid

Non-specific Defense Second Line Defense: Internal Antimicrobial proteins Interferons – antiviral Complement – immunity, allergies and inflammation Natural killer (NK) cells Lymphocytes kill microbes and tumor cells Phagocytes Wandering phagocytes Fixed phagocytes

Non-specific Defense Second Line Defense: Internal Inflammation Mast cells and basophils release chemicals Arterioles vasodilate – more blood to site Increased capillary permeability – more fluid into tissues

Non-specific Defense Inflammation results in Redness Heat Swelling (edema) Pain Healing

Specific Defense: Immunnity Study of immunity is immunology Immunity versus non-specific defense Specificity: responds to specific antigens Memory: Second exposure to antigen causes a stronger response Antigens Foreign (non-self) chemicals Cause immune response

Immunity B-cell and T-cell lymphocytes responsible for immunity Two types of immune responses Cell mediated immunity: T-cells respond to intracellular antigens such as virus infected cells and tumor cells Antibody mediated immunity: B-cells respond to extracellular antigens such as bacteria

Cell Mediated Immunity T-cells processed by thymus gland Two types of T-cell lymphocytes CD4 cells (Helper cells) Activated when antigen presented by antigen presenting cell (APC) cell Develops into helper T-cells and memory cells Helper T-cells must stimulate CD8 cells for them to become fully activated killer T’s CD8 cells (Cytotoxic cells) Activated by contact with virus infected body cell Develop into killer t-cells and memory cells

Cell Mediated Immunity Cytotoxic T’s leave lymphatic tissue to search for and destroy virus infected cells, tumor cells and tissue transplant cells on contact

Cell Mediated Immunity

Antibody Mediated Immunity B-cell lymphocytes stay in lymph tissues Extracellular antigen enters lymph tissue and binds to B-cell receptors B-cells become activated B-cells divide (clone) to form plasma cells and memory cells Helper T-cells bind to antigen on B-cells and “help” stimulate plasma cell and memory cell formation

Antibody Mediated Immunity Plasma cells secrete various types of antibodies Antibodies bind to the specific antigen that activated its parent B-cells Antibodies cause the destruction of the antigen

Antibody Mediated Immunity Antibodies destroy antigens by Neutralizing antigens such as toxins Agglutinating (clumping) and precipitating (removing from solution) antigen bearing cells Activating the complement proteins that destroy the antigen by various means Enhancing phagocytosis

Antibody Mediate Immunity

Immune Response Primary Response After an initial exposure to an antigen a slow rise in antibodies production occur first as immunoglobulin M (IgM) then (IgG) Secondary Response After a subsequent exposure the antibodies production is far greater and is mainly (IgG)

Summary of Cell and Antibody Mediated Immunity