Chapter 14 Lymphatic System PDF

# Seeley's Essentials of Anatomy & Physiology, Tenth Edition ## Chapter 14: Lymphatic System and Immunity ### Lecture Outline **Functions of the Lymphatic System:** 1. Fluid balance 2. Fat Absorption 3. Defense ### Lymphatic System and Lymph Drainage: - **Right Lymphatic Duct:** - Where lym...

# Seeley's Essentials of Anatomy & Physiology, Tenth Edition ## Chapter 14: Lymphatic System and Immunity ### Lecture Outline **Functions of the Lymphatic System:** 1. Fluid balance 2. Fat Absorption 3. Defense ### Lymphatic System and Lymph Drainage: - **Right Lymphatic Duct:** - Where lymphatic vessels from the right upper limb and right head, neck, and chest empty - Empties into right subclavian vein - **Thoracic Duct:** - Rest of body empties from lymphatic vessels - Empties into left subclavian vein ### Components of the Lymphatic System: - **Lymph:** Fluid that enters lymphatic capillaries composed of water and some solutes - **Lymphocytes:** White blood cells - **Lymphatic Vessels:** Transport lymph - **Lymph Nodes:** Filter lymph - **Tonsils:** Lymphatic tissue in the throat - **Spleen:** Filters blood and stores lymphocytes - **Thymus Gland:** Produces and matures lymphocytes ### Lymphatic Capillaries - Tiny, closed-ended vessels - Fluid moves easily into - Found in most tissues - Join to form lymphatic vessels ### Lymph Formation and Movement - Fluid from blood capillaries enters tissue spaces - Lymphatic capillaries collect fluid and become lymph - Valves prevent lymph from flowing backwards - Lymph moves towards the heart ### Lymphatic Organs: - **Tonsils:** - **Palatine Tonsils:** On each side of the oral cavity - **Pharyngeal Tonsils:** Near the internal opening of the nasal cavity (adenoid) - **Lingual Tonsils:** Posterior surface of the tongue - Form a protective ring of lymphatic tissue around the nasal and oral cavities - **Lymph Nodes:** - Rounded structures that vary in size - Located near lymphatic vessels - Found in groin, armpit, and neck - Lymph passes through lymph nodes before entering blood - Lymph moves through lymph nodes, and the immune system is activated by the production of lymphocytes if foreign substances are detected - Remove microbes by macrophages - **Spleen:** - Size of a clenched fist - Located in the abdomen - Filters blood - Detects and responds to foreign substances - Destroys old red blood cells - Blood reservoir - **White Pulp:** Lymphatic tissue surrounding arteries - **Red Pulp:** Contains macrophages and red blood cells that connect to veins - **Thymus Gland:** - Bilobed gland - Located in the mediastinum behind the sternum - Stops growing at age 1 - Decreases in size at age 60 - Produces and matures lymphocytes ### Immunity - **Immunity:** The ability to resist damage from foreign substances - **Types of Immunity:** - **Innate Immunity:** Present at birth, defends against any pathogen - **Adaptive Immunity:** Acquired after birth, reacts when innate defenses don't work #### Innate Immunity - First line of defense: Physical barriers such as skin and mucous membranes - Chemical mediators: - **Lysozyme:** Found in tears and saliva to kill bacteria - **Mucous Membranes:** Prevent the entry of microbes - **Histamine:** Promotes inflammation by causing vasodilation - **Interferons:** Proteins that protect against viral infections by stimulating surrounding cells to produce antiviral proteins - Cells of the immune system: - **Phagocytic Cells:** - **Neutrophils:** First to respond to an infection but die quickly - **Macrophages:** Initially were monocytes, leave blood and enter tissues, more potent at ingesting microbes than neutrophils, protect lymph in lymph nodes and blood in spleen and liver. Given specific names for certain areas of the body (Kupffer cells in the liver) - **Eosinophils:** Produced in red bone marrow, release chemicals to reduce inflammation - **Basophils:** Made in red bone marrow, leave blood and enter infected tissue, can release histamine - **Mast cells:** Made in red bone marrow, found in skin, lungs, gastrointestinal tract, urogenital tract, can release leukotrienes - **Natural Killer Cells:** Type of lymphocyte, produced in the red bone marrow, recognize classes of cells such as tumor cells or virus infected cells, release chemicals to lyse cells - **Inflammatory Response:** Involves chemicals and cells due to injury, signaled by the presence of foreign substances, stimulates the release of chemical mediators #### Adaptive Immunity - Defense that involves specific recognition to a specific antigen. - **Acquired after birth** - **Reacts when innate defenses don't work** - **Slower than innate immunity ** - **Has memory ** - **Uses lymphocytes (B and T cells)** - **2 types:** - **Antibody-Mediated Immunity:** Effective against antigens in body fluids such as blood and lymph, effective against bacteria, viruses, and toxins - **Cell-Mediated Immunity:** Used against antigens in cells and tissue, is effective against intracellular bacteria, viruses, fungi, and protozoa ##### Terms Related to Adaptive Immunity - **Antigen:** Substance that stimulates an immune response; examples include bacteria, virus, pollen, food, and drugs - **Self-Antigen:** A molecule produced by the person's body that stimulates an immune system response - **Antibody:** Proteins the body produces in response to an antigen ##### Origin and Development of Lymphocytes - **Stem Cells:** - Found in red bone marrow - Give rise to all blood cells - Give rise to some pre T cells and pre B cells - **Lymphocytes:** - Type of white blood cell - Involved in adaptive immunity - Develop from stem cells - Differentiate into specific lymphocytes such as B or T cells - **B Cells:** - Type of lymphocyte - Involved in antibody-mediated immunity - Originate from stem cells - Mature in red bone marrow - Move to lymphatic tissue after maturation - Lead to the production of antibodies - **T Cells:** - Type of lymphocyte - Involved in cell-mediated immunity primarily and antibody-mediated immunity - Mature in the thymus gland - Move to lymphatic tissue after maturation - 4 types: - Helper T Cells: Activate macrophages, help form B cells, promote production of cytotoxic T Cells - Cytotoxic T Cells: Precursor to cytotoxic T lymphocytes (CTL) - Cytotoxic T Lymphocytes: Destroys antigen on contact - Regulatory T Cells: Turn off the immune system response when antigen is gone ##### Antigen Recognition - Lymphocytes have antigen receptors on their surface - B-cell receptors on B cells and T-cell receptors on T cells - Each receptor only binds with a specific antigen - When antigen receptors combine with the antigen, the lymphocyte is activated and adaptive immunity begins ##### The MHC Molecule - Major histocompatibility complex molecule (MHC): - Contain binding sites for antigens - Specific for certain antigens - Hold and present a processed antigen on the surface of the cell membrane - Bind to antigen receptors on B or T cells and stimulate a response ##### Cytokines - Proteins secreted by a cell that regulates neighboring cells - **Interleukin-1:** Released by macrophages, stimulates helper T cells ##### Proliferation of Helper T Cells - **Antigen Presenting Cells:** - Phagocytize antigens, process the antigen, and display it on the cell's surface. - Antigen is bound to MHC class II molecules. - The T-cell receptor of the helper T cell recognizes the antigen. - **Costimulation:** - Interleukin-1 is secreted by macrophages. - CD4 glycoprotein on the helper T cells binds to interleukin-1. - **Interleukin-2:** - Stimulates the helper T cell to secrete interleukin-2. - Causes the production of interleukin-2 receptors. - The helper T cell is stimulated to divide when interleukin-2 binds to receptors. - **Daughter Helper T Cells:** - Stimulated to divide again when exposed to the same antigen. - Greatly increase the number of helper T cells. - **The increased number of helper T cells:** - Helps to activate B cells or effector T cells. ##### Lymphocyte Proliferation 1. After the antigen is processed and present to helper T cells, the helper T cell produces interleukin-2 and interleukin-2 receptors. 2. Interleukin-2 binds to receptors and stimulates more helper T cells production. 3. Helper T cells are needed to produce B cells. 4. B cells produce antibodies. ##### Proliferation of B Cells - **Antigen:** Bound to a B-cell receptor. - **Receptor and Antigen:** Taken into the cell by endocytosis. - **MHC class II molecule:** Used to present the processed antigen to the helper T cell. - **T-cell receptor:** Binds to the MHC class II/antigen complex. - **Costimulation:** - CD4 and other surface molecules. - Interleukins (cytokines) released from the helper T cells. - **B-cells divide.** - **Daughter cells divide.** - **Many cells produce antibodies.** ##### Dual Nature of the Immune System - Lymphocytes give rise to 2 types of immune responses: antibody-mediated and cell-mediated - Antigens can trigger both types of responses - Both types are able to recognize self versus nonself, use specificity, and have memory ##### Antibody-Mediated Immunity - Effective against antigens in body fluids (blood and lymph) - Effective against bacteria, viruses, and toxins - Uses B cells to produce antibodies ##### Antibody Structure - Letter Y shape - **Variable Region:** - V of Y - Bind to epitopes of antigen using antigen-binding sites - **Constant Region:** - Stem of Y - Each class of immunoglobulin has the same structure - 5 classes of immunoglobulins used to destroy antigens: - IgG - IgM - IgA - IgE - IgD ##### Antibodies - **IgG:** 80 to 85% in serum, Activates complement and increases phagocytosis, can cross the placenta and provide protection to the fetus, Responsible for Rh reactions, such as hemolytic disease of the newborn - **IgM:** 5 to 10% in serum, Activates complement, acts as an antigen-binding receptor on the surface of B cells, Responsible for transfusion reactions in the ABO blood system, often the first antibody produced in response to an antigen - **IgA:** 15% in serum, Secreted into saliva, into tears, and onto mucous membranes, Protects body surfaces, Found in colostrum and milk to provide immune protection to the newborn - **IgE:** 0.002% in serum, Binds to mast cells and basophils and stimulates the inflammatory response - **IgD:** 0.2% in serum, Functions as an antigen-binding receptor on B cells ##### Effects of Antibodies - Inactivate antigens - Bind antigens together - Activate complement cascades - Initiate the release of inflammatory chemical - Facilitate phagocytosis ##### Antibody Production - **Primary Response:** - 1st exposure of B cell to antigen - B cell undergoes division and forms plasma cells and memory cells - **Plasma Cells:** Produce antibodies - 3 to 14 days to by effective against antigen, person develop disease symptoms - **Secondary Response:** - **Memory Cells:** - Occurs when the immune system is exposed to an antigen that has been seen before. - B memory cells quickly divide to form plasma cells which produce antibodies. - Produces new memory cells. ##### Cell-Mediated Immunity - Used against antigens in cells and tissues. - Effective against intracellular bacteria, viruses, fungi, and protozoa. - Uses different types of T cells. ##### Types of T Cells for Cell-Mediated Immunity - **Helper T Cells:** Activate macrophages, help form B cells, promote production of cytotoxic T cells. - **Cytotoxic T Cells:** Precursor to cytotoxic T lymphocytes (CTL) - **Cytotoxic T Lymphocytes:** Destroys antigen on contact. - **Regulatory T Cells:** Turn off the immune system response when antigen is gone ##### Proliferation of Cytotoxic T Cells 1. MHC class I molecule displays an antigen on the surface of a target cell. 2. The activation of a cytotoxic T cell begins when the T-cell receptor binds to the MHC class I/antigen complex. 3. Costimulation of the cytotoxic T cell by CD8 and other surface molecules. 4. Costimulation by cytokines such as interleukin-2 released from helper T cells. 5. The activated cytotoxic T cell divides. ##### Stimulation and Effects of T cells - **Activation of a cytotoxic T cell:** By antigen on the surface of a cell. - **Cytotoxic T cells:** Release cytokines, kill cells on contact, produce inflammation, initiate phagocytosis, and activate T cells ##### Immune Interactions - Overview of immune interactions between the innate and adaptive immune systems ##### Types of Adaptive Immunity: - **Naturally Acquired Immunity** - Acquired after exposure to an antigen - **Active:** Natural exposure to antigens causes the production of antibodies. - **Passive:** Transfer of antibodies from mother to child. - **Artificially Acquired Immunity** - Acquired after exposure to a vaccine or injection of antibodies - **Active:** Injection of antigens using vaccines which cause the production of antibodies. - **Passive:** Injection of antibodies from another person or animal. ##### Ways to Acquire Adaptive Immunity - **Acquired Adaptive Immunity:** - **Active Immunity:** Immunity is provided by the individual's own immune system. - **Natural:** Antigens are introduced through natural exposure. - **Artificial:** Antigens are deliberately introduced in a vaccine. - **Passive Immunity:** Immunity is transferred from another person or animal. - **Natural:** Antibodies from the mother are transferred to her child across the placenta or in milk. - **Artificial:** Antibodies produced by another person or an animal are injected.