Lymphatic-System-and-Immunity.pdf

Lymphatic System and Immunity lymphatic system important to the defense of the body, also plays a role in maintaining the fluid balance as well as in the absorption of lipids in the digestive tract Immunity involves the activity of tissues, cells, and molecules protecting the body...

Lymphatic System and Immunity lymphatic system important to the defense of the body, also plays a role in maintaining the fluid balance as well as in the absorption of lipids in the digestive tract Immunity involves the activity of tissues, cells, and molecules protecting the body from damage. Functions of Lymphatic System 1. Fluid balance 2. Liquid absorption 3. Defense Lymphatic vessels Essential for the maintaining of fluid balance Lymphatic Capillaries One-way valve lymph Excess fluid passes through the tissue spaces and enters lymphatic capillaries forming a clear fluid lymphatic capillaries most tissues of the body Areas of the body that lack lymphatic vessels are the CNS, the bone marrow, and tissues without blood vessels, such as cartilage, epidermis, and the cornea Different structure from blood capillaries lack a basement membrane  Lymphatic system includes lymph, lymphatic vessels, lymphatic tissues, lymphatic nodules, lymph nodes, the tonsils, the spleen, and the thymus.  Lymph Formation and movement function as a series of one-way valves that allow fluid to enter the capillary but prevent it from passing back into the interstitial spaces.  Lymph moves through lymphatic vessels by three mechanism:  1. Contraction of lymphatic vessels. In many parts of the body lymphatic vessels actually pump lymph along the vessel by way of smooth muscle contractions. 2.Contraction of skeletal muscles surrounding skeletal muscle cells contract, lymphatic vessels are compressed, causing lymph to move.  3.Thoracic pressure changes. During inspiration, pressure the thoracic cavity decreases, lymphatic vessels expand, and lymph flows into them. Layers of Lymphatic Vessels Inner layer: endothelium surrounded by an elastic membrane Middle layer: smooth muscle cells and elastic fibers Outer layer: thin layer of fibrous connective tissue  Lymph moves through lymphatic vessels by three mechanisms: 1. Contraction of lymphatic vessels 2. Contraction of skeletal muscles 3. Thoracic pressure changes Lymph nodes round, oval, or bean-shaped bodies distributed along the various lymphatic vessels filters lymph, which enters and exits the lymph nodes through the lymphatic vessels The lymphatic vessels converge to form larger vessels called lymphatic trunks jugular trunks - drain lymph from the head and neck subclavian trunks - drain lymph from the upper limbs, superficial thoracic wall, and mammary glands bronchomediastinal trunks - drain lymph from the thoracic organs and the deep thoracic wall. intestinal trunks - drain lymph from abdominal organs, such as the intestines, stomach, pancreas, spleen, and liver. lumbar trunks - drain lymph from the lower limbs, pelvic and abdominal walls, pelvic organs, ovaries or testes, kidneys, and adrenal glands. (a) Anterior view of the major lymphatic vessels in the thorax and abdomen (b) Close-up view of the lymphatic vessels from which lymph enters the blood. The lymphatic trunks either connect to large veins in the thorax or join to yet larger vessels called lymphatic ducts, which then connect to the large veins. (c) Regions of the body drained by the right and left lymphatic vessels. Lymph drainage into vein thoracic duct largest lymphatic vessel in the body approximately 38–45 cm in length, extending from the twelfth thoracic vertebra to the base of the neck drains lymph from the right side of the body inferior to the thorax and the entire left side of the body (b) Close-up view of the lymphatic vessels from which lymph enters the blood. (c) Regions of the body drained by the right and left lymphatic vessels. In a small proportion of cases, the lymphatic trunks form a sac called the cisterna chyli Lymphatic Tissue and Organs  Lymphatic organs contain lymphatic tissue, which consists primarily of lymphocytes but also includes macrophages, dendritic cells, reticular cells, as well as other cell types.  Two Functional Classes 1. primary lymphatic organs - consists of red bone marrow and the thymus 2. secondary lymphatic tissue and organs - consists of lymphatic nodules, including the tonsils, and diffuse lymphatic tissue, as well as lymph nodes and spleen Lympathic Organs Could be distinguished from the lymphatic tissue by the presence of a connected tissue capsule. Lympathic Tissues Generally more diffuse and are not surrounded by a capsule, or known nonencapsulated Associated with mucous membrane digestive, respiratory, urinary, and reproductive tracts. Refers to Mucosa-associated lymphatic tissue (MALT) Reticular Fibers Both Lymphatic and Tissue Organ both consist of this, along with lymphocytes and other immune cells. The cells attach to the reticular fibers that forms a network that filters microorganisms and other foreign substance. Diffuse Lymphatic Tissue and Lymphatic Nodules Diffuse lymphatic tissue contains dispersed lymphocytes, macrophages, and other cells has no clear boundary and blends with surrounding tissues Lymphatic nodules are denser arrangements of lymphatic tissue organized into compact, somewhat spherical structures ranging in size from a few hundred microns to a few millimeters or more in diameter Large collections of lymphatic nodules are found in certain areas of the body includes Peyer patches and tonsils. Peyer patches - aggregations of lymphatic nodules in the distal half of the small intestine Tonsils - are large groups of lymphatic nodules and diffuse lymphatic tissue located deep to the mucous membranes within the pharynx Three types of tonsils: 1. the palatine tonsils 2. pharyngeal tonsil 3. lingual tonsil 1.palatine tonsils - are relatively large, oval, lymphatic masses on each side of the junction between the oral cavity and the pharynx. 2.pharyngeal tonsils - is a collection of somewhat closely aggregated lymphatic nodules near the junction between the nasal cavity and the pharynx. adenoids - when the pharyngeal tonsil is enlarged 3.lingual tonsil - is a loosely associated collection of lymphatic nodules on the posterior surface of the tongue. Lymph Nodes Lymph Nodes are small, round or bean-shaped structures ranging from 1 mm to 25 mm long. are distributed along the course of the lymphatic vessel to filter the lymph, removing bacteria and other materials categorized as superficial or deep. Superficial lymph nodes - are in the subcutaneous tissue beneath the skin deep lymph nodes - are everywhere else Most superficial and deep lymph nodes are located near or on blood vessels and is approximately 450 lymph nodes are distributed throughout the body. ∙ Cervical and head lymph nodes (about 70) filter lymph from the head and neck. ∙ Axillary lymph nodes (about 30) filter lymph from the upper limbs and superficial thorax. ∙ Thoracic lymph nodes (about 100) filter lymph from the thoracic wall and organs. ∙ Abdominopelvic lymph nodes (about 230) filter lymph from the abdomen and pelvis. ∙ Inguinal and popliteal lymph nodes (about 20) filter lymph from the lower limbs and the superficial pelvis. Capsule - dense connective tissue that surrounds each lymph node Trabeculae - extensions of the capsule that form a delicate internal skeleton in the lymph node.  In some areas of the lymph node, lymphocytes and macrophages are packed around the reticular fibers to form lymphatic tissue; in other areas, the reticular fibers extend across open spaces to form lymphatic sinuses.  Both the lymphatic tissues and sinuses are arranged into two indistinct layers. An Outer cortex and inner medulla. Cortex Inner Medulla consists of a subcapsular sinus, Consist of Medullary Cords beneath the capsule, and that is an organized branching cortical sinuses, which are of irregular strands of diffuse separated by diffuse lymphatic lymphatic tissue which are tissue, trabeculae, and seperated by the medullary lymphatic nodules. sinuses.  Affarent Lymphatic Effarent Lymphatic Vessels Vessels Carry filtered lymph Carry filtered lymph toward the Lymph away the Lymph nodes nodes Macrophages Lining of the lymphatic sinuses Remove bacteria and other foreign substances Germinal Centers spleen spleen is roughly the size of a clenched fist and is located on the left, superior part of the abdominal cavity Average weight of an adult spleen: Male: 180 g Female: 140 g White pulp is lymphatic tissue surrounding the arteries within the spleen Red pulp is associated with the veins within the spleen consists of a fibrous network, filled with macrophages and red blood cells, and enlarged capillaries that connect to the veins. Approximately one-fourth of the volume of the spleen is white pulp, and three-fourths is red pulp.  Branches of the splenic artery enter the spleen at the hilum, and their branches follow the various trabeculae into the spleen Thymus  Thymus is a bilobed gland located in the superior mediastinum, the partition dividing the thoracic cavity into the left and right parts. Immunity Immunity is the ability to resist damage from foreign substances, such as microorganisms; harmful chemicals, such as toxins released by microorganisms; and internal threats, such as cancer cells. is categorized as innate immunity (also called nonspecific resistance) and adaptive immunity (also called specific immunity) In innate immunity, the body recognizes and destroys certain foreign substances, but the response to them is the same each time the body is exposed. In adaptive immunity, the body recognizes and destroys foreign substances, but the response to them is faster and stronger than the first time the foreign substance was encountered. Specificity - is the ability of adaptive immunity to recognize a particular substance. Memory - is the ability of adaptive immunity to “remember” previ ous encounters with a particular substance Innate immunity main components of innate immunity: 1. physical barriers that prevent microbes from entering the body to prevent entry of disease-causing agents in the body. 2. chemical mediators that act directly against microorganisms or activate other mechanisms, leading to the destruction of the microorganisms; and 3. cells involved in phagocytosis and the production of chemicals that participate in the immune response. Physical Barriers Chemical Mediators Chemical mediators molecules responsible for many aspects of innate immunity histamine, complement, and eicosanoids Cytokines are proteins or peptides secreted by cells Complement - is a group of about 20 proteins that protect the body by destroying abnormal cells or enhancing other components of immunity. Complement proteins make up approximately 10% of the globulin part of plasma proteins. They include proteins named C1–C9 and factors B, D, and P (properdin).  Interferons are proteins that protect the body against viral infection and perhaps some forms of cancer Complement Cascade White blood cells White blood cells and the cells derived from them are the most important cellular components of the immune system. White blood cells are produced in red bone marrow and lymphatic tissue and are released into the blood, where they are transported throughout the body. are attracted to chemical signals called chemo tactic factors. Phagocytosis- is the endocytosis and destruction of particles by cells called phagocytes Neutrophils - are small, phagocytic cells produced in large numbers in red bone marrow and released into the blood, where they circulate for a few hours. Macrophages - are large phagocytic cells, derived from monocytes, one of the classes of white blood cells Basophils and Mast Cells play important roles in stimulating inflammation. Basophils - are white blood cells derived from red bone marrow, are motile cells that can leave the blood and enter infected tissues. Mast cells - which are also derived from red bone marrow, are nonmotile cells in connective tissue, especially near capillaries. Eosinophils are produced in red bone marrow, enter the blood, and within a few minutes enter tissue numbers increase in response to parasitic infections secrete enzymes that effectively kill some parasites  Natural killer (NK) cells These lymphocytes are produced in red bone marrow and account for up to 15% of lymphocytes. Not part of an adaptive community, but classified as part of innate immunity.  Inflammatory Response is a complex sequence of events involving many of the chemical mediators and cells of innate immu- nity. Trauma, burns, chemicals, and infections can damage tissues, resulting in inflammation.  Inflammation can be local or systemic Local inflammation - is an inflammatory response confined to a specific area of the body Systemic inflammation is an inflammatory response that occurs in many parts of the body Adaptive Immunity adaptive immunity ability of lymphcytes to recognize, respond to, and “remember” a particular substance involves two major types of lymphocytes: B cells and T cells can be divided into antibody-mediated immunity and cell- mediated immunity. Antibody-mediated immunity - involves proteins called antibod ies, which are found in extracellular fluids, such as the plasma of blood, interstitial fluid, and lymph. Cell-mediated immunity involves the actions of T cells. Antigens divided into two groups: foreign antigens and self antigens. Foreign antigens - are not produced by the body but are introduced from outside it. Self- antigens - are molecules the body produces to stimulate an adaptive immune system response.  Antigenic Determinants and Antigen Receptors Lymphocytes must interact with and recognize an antigen. Has Multiple epitopes Has a clone called Antigen Receptors Haptens and Allergic Reactions Haptens - often referred to as incomplete antigens, are small molecules (of low molecular weight) that can com- bine with large molecules, such as blood proteins, to stimu- late an adaptive immune response  Major Histocompatibility Complex Molecules Most lymphocyte activa tion involves interaction with major histocompatibility complex (MHC) molecules. MHC molecules - are glycoproteins found on the plasma membranes of most of the body’s cells  Two classes of MHC molecules are present in the body: (1) MHC class I molecules display endogenous antigens; (2) MHC class II molecules display exogenous antigens.  MHC class I molecules found on nucleated cells display endogenous antigens on the cell’s plasma membrane. MHC class I molecules The MHC class I/antigen complex functions as a signal or “red flag” that prompts the immune system to destroy the displaying cell. Self-antigens moves foreign protein fragments to the cell’s plasma membrane can also inadvertently transport self- protein fragments. MHC class II molecules display exogenous antigens and are found on phagocytic cells called antigen- presenting cells. Clonal selection is the mechanism that results in a large population of identical lymphocytes, called clones. occurs when a lymphocyte proliferates (divides repeatedly) and differentiates (becomes specialized) when exposed to a specific antigen.  positive selection - process results in the survival of pre-B and pre-T cells that are capable of an immune response. negative selection process eliminates or suppresses clones acting against self-antigens, thereby preventing the destruction of a person’s own cells.  Costimulation is accomplished by cytokines released from cells as well as molecules attached to the surfaces of cells  Activation of Lymphocytes 1. Lymphocytes must be able to recognize the antigen; 2. After recognition, the lymphocytes must increase in number to destroy the antigen Lymphocyte Proliferation Inhibition of Lymphocytes Tolerance - is a state of unresponsiveness of lymphocytes to a specific antigen. Tolerance can be induced in three primary ways: 1. Deletion of self-reactive lymphocytes. 2. Prevention of the activation of lymphocytes 3. Activation of regulatory T cells.  Proliferation of Helper T Cells An antigen-presenting cell (macrophage) stimulates helper T cells to divide and produce cytokine  Tolerance can be induced in three primary ways: 1. Deletion of self-reactive lymphocytes. During prenatal devel opment and after birth, stem cells in red bone marrow and the thymus give rise to immature lymphocytes that develop into mature lymphocytes capable of an immune response.  2. Prevention of the activation of lymphocytes. For lymphocytes to be activated, two signals are usually required: (1) the MHC/ antigen complex binding with an antigen receptor and (2) costimulation. 3. Activation of regulatory T cells. Regulatory T cells, also called suppressor T cells, are a poorly understood group of T cells that are defined by their ability to suppress immune responses. Antibody-Mediated Immunity Antibody-mediated immunity involves the production of antibodies in response to extracellular antigens. Antibodies are proteins produced in response to an antigen. Large numbers of antibodies exist in plasma, although plasma also contains other proteins. sometimes called gamma globulins because they are found mostly in the γ-globulin part of plasma, or immunoglobulins (Ig) Effects of Antibodies can be described as direct effects or indirect effects Direct effects of antibodies include the following: (1) The antibody can bind to the antigenic determinant and interfere with the antigen’s ability to function (2) the antibody can combine with an antigenic determinant on two different antigens, rendering the antigens ineffective Indirect effects of antibodies include the following: 1. When an antibody (IgG or IgM) combines with an antigen through the variable region, the constant region can activate the complement cascade through the classical pathway 2. The antibodies attach to mast cells or basophils through their constant region 3. An antibody (IgG) acts as anopsonin by connecting to an antigen through the variable region of the antibody and to a macrophage through the constant region of the antibody  Effect of Antibodies The effects of antibodies can be described as direct effects or indirect effects.  Although antibodies can directly alter antigen function, most of their effectiveness results from indirect mechanisms: 1. When an antibody (IgG or IgM) combines with an antigen through the variable region, the constant region can activate the complement cascade through the classical pathway  2. Antibodies (IgE) can initiate an inflammatory response 3. Opsonins (OP-soh-ninz) are substances that make an antigen more susceptible to phagocytosis Antibody Production  The first exposure of a B cell to an antigen for which it is specific causes the primary response  The secondary response, or memory response, occurs when the immune system is exposed to an antigen against which it has already produced a primary response Cell-Mediated Immunity is most effective against cytoplasmic micro organisms through the action of cytotoxic T cells responding to endogenous antigens. The other branch of adaptive immunity is cell-mediated immunity. Proliferation of Cytotoxic T Cells Cytotoxic T cells increase in number in response to an abnormal MHC class I molecule  Stimulation and Effects of T Cells When activated, cytotoxic T cells form many additional cytotoxic T cells, as well as memory T cells. The cytotoxic T cells release cytokines that promote the destruction of the antigen or cause the lysis of target cells, such as virus-infected cells, tumor cells, or transplanted cells. Acquired adaptive immunity Adaptive immunity can be broken down into four types, based on the way it is acquired: (1) active natural (2) active artificial (3) passive natural (4) passive artificial Active immunity results when an individual is exposed to an antigen (either naturally or artificially) and the response of the individual’s immune system is the cause of the immunity. Passive immunity occurs when another person or an animal develops immunity and the immunity is transferred to a non immune individual. Systemic Lupus Erythematosus is an autoimmune disease, meaning that tissues and cells are damaged by the body’s own immune system. The name describes the skin rash that is characteristic of the disease Antiserum - is the general term for the injection that contains antibodies responsible for passive artificial immunity. immunotherapy - treats disease by altering immune system function or by directly attacking harmful cells QUIZ time! QUIZ