THE LYMPHATIC SYSTEM Chapter 15

Introduction Transports lymph through lymphatics Lymphatics: lymph capillaries and vessels Controls body fluid Destroys harmful microorganisms

THE FUNCTIONS OF THE SYSTEM AND THE STRUCTURE AND FUNCTIONS OF THE LYMPHATIC VESSELS

Introduction Drain interstitial fluid from tissue spaces –Prevent edema Transport digested fat to blood –Lacteals: special lymphatics in small intestine –Chyle: milky lymph in lacteals Develop immunities Produce lymphocytes

Lymphatic Vessels Lymph capillaries: blind-end tubes Lymph capillaries are located between cells Lymph capillaries unite to form lymphatics Lymphatics converge into two main channels –Thoracic duct and right lymphatic duct

Lymph Nodes Found along lengths of lymphatics Efferent: exit lymph node at the hilum Afferent: enter lymph node at various locations Trabeculae: divide the node into compartments

Lymph Nodes (cont’d.) Germinal centers of compartments produce lymphocytes

LYMPH CIRCULATION

Lymph Circulation (cont’d.) Interstitial fluid: plasma in interstitial spaces Lymph: interstitial fluid in lymph capillaries –Passes into lymphatics Lymphatics join to form lymph trunks

Lymph Circulation (cont’d.) Lymph circulation maintained by: –Normal skeletal muscle contractions Compresses lymph vessels and forces lymph in one direction –Respiratory or breathing movements –Smooth muscle in lymphatic vessels

Lymph Circulation (cont’d.) Lymph trunks –Lumbar: drains lower extremities and pelvis –Intestinal: drains abdominal region –Bronchomediastinal and intercostal: drain thorax –Subclavian: drains upper extremities –Jugular: drains head and neck

Lymph Circulation (cont’d.) Individual trunks drain into two main trunks –Thoracic duct: drains into the left subclavian vein –Right lymphatic duct: drains into the right subclavian vein

THE ORGANS OF THE LYMPHATIC SYSTEM

The Organs of the Lymphatic System (cont’d.) Tonsils –Palatine, pharyngeal and lingual –Protect the nose and oral cavity Thymus: lymphocyte production and maturation Peyer’s patches: found in walls of small intestine

The Organs of the Lymphatic System (cont’d.) Spleen –Largest mass of lymphatic tissue –Phagocytizes worn-out RBCs and platelets Recycles hemoglobin –Produces lymphocytes and plasma cells –Stores blood for release during hemorrhage

The Organs of the Lymphatic System (cont’d.) External view of the Spleen

IMMUNITY

Immunity (cont’d.) Ability of body to resist –Infection from pathogens –Damage from foreign substances and harmful chemicals

Immunity (cont’d.) Humoral immunity –B lymphocytes: produce antibodies Fight circulating bacteria and viral infections Become plasma cells when they enter tissues

Immunity (cont’d.) Cellular immunity –T lymphocytes Come from thymus glands Fight intracellular viruses, fungi, parasites, cancer

ANTIGENS AND ANTIBODIES

Antigens and Antibodies (cont’d.) Antigen: foreign protein in our body B lymphocytes –Produce antibodies in response to antigens –Antibodies bind to specific antigen –Antigens precipitate –Phagocytic WBCs eat the antigens

Antigens and Antibodies (cont’d.) Antibody morphology –Four amino acid chains linked by disulfide bonds Heavy and light chains –Y shaped molecule –Binding sites at tips of Y –Stem of the Y is always constant

Antigens and Antibodies (cont’d.) Antibody types –IgG: attacks viruses, bacteria, and toxins; activates complement –IgA: found in exocrine gland secretions –IgM: response to bacteria or food antigens –IgD: found on surface of B lymphocytes –IgE: associated with allergic reactions

Antigens and Antibodies (cont’d.) Active immunity: B cells contact antigen and produce antibodies –Natural active: exposure to infection –Artificial active: vaccine Passive immunity –Natural passive: maternal antibodies to fetus –Artificial passive: gamma globulin

CELLS OF THE IMMUNE RESPONSE AND OTHER DEFENSES

Cells of the Immune Response and Other Defenses (cont’d.) B cells: antigen –Antibody binding Plasma cells: replicated B cells Helper T cells: stimulate production of –Killer T cells –More B cells

Cells of the Immune Response and Other Defenses (cont’d.) Killer T cells: –Attack virus-invaded body cells –Attack cancer cells –Reject body grafts Memory cells: descendants of activated T and B cells

Cells of the Immune Response and Other Defenses (cont’d.) Suppressor T cells: slow down activities of B and T cells Macrophages –Engulf and digest antigen –Present then to T cell for recognition Lymphokines: chemicals released by sensitized T cells

Cells of the Immune Response and Other Defenses (cont’d.) Monokines: chemicals released by activated macrophages Skin: mechanical barrier –Acid mantle, sebum Lysozyme: (tears and saliva) attacks bacteria

Cells of the Immune Response and Other Defenses (cont’d.) Mucous membranes: trap microorganisms and debris Hydrochloric acid: (stomach) destroys microorganisms

Animation – Lymphatic System Click Here to Play Lymphatic System Animation

Summary Discussed the functions of the immune system Described lymph and its flow through the body Discussed the functions of the spleen and tonsils

Summary (cont’d.) Described the different types of immunity Discussed the immune response