Seeley's Essentials of Anatomy & Physiology Tenth Edition (PDF)

# Seeley's Essentials of Anatomy & Physiology, Tenth Edition This document appears to be a lecture outline for a course in Anatomy & Physiology. The document includes outlines, diagrams, and other informative content. ## Chapter 14: Lymphatic System and Immunity ### Functions of the Lymphatic Sy...

# Seeley's Essentials of Anatomy & Physiology, Tenth Edition This document appears to be a lecture outline for a course in Anatomy & Physiology. The document includes outlines, diagrams, and other informative content. ## Chapter 14: Lymphatic System and Immunity ### Functions of the Lymphatic System 1. Fluid Balance 2. Fat Absorption 3. Defense ### Lymphatic System and Lymph Drainage - The Lymphatic System is responsible for fluid balance, fat absorption, and defense. - It includes lymph nodes, spleen, and thymus gland. ### Components of the Lymphatic System - **Lymph:** fluid that travels throughout the body through a system of lymphatic capillaries and vessels and is comprised of water and solutes. - **Lymphocytes:** white blood cells crucial for immune response. - **Lymphatic Vessels:** tiny vessels that resemble veins; contain one-way valves that allow lymph to flow in one direction towards the veins. - **Lymph Nodes:** small, rounded structures positioned at the junctions of lymphatic vessels. - **Tonsils:** clusters of lymphatic tissue located in the throat, acting as a first line of defense against pathogens. - **Spleen:** a large lymphatic organ located in the abdomen that filters blood, stores blood cells, and destroys old red blood cells. - **Thymus Gland:** a small, bilobed gland located above the heart that produces and matures lymphocytes. ### Lymphatic Capillaries - These are tiny, closed-ended vessels that move fluid easily into the bloodstream. - They join together to form lymphatic vessels. ### Lymphatic Vessels - Lymphatic vessels resemble small veins, receiving lymph from lymphatic capillaries. - **Right Lymphatic Duct:** receives lymph from the right upper limb and right side of the head, neck, and chest, and empties into the right subclavian vein. - **Thoracic Duct:** receives lymph from the rest of the body and empties into the left subclavian vein. ### Lymph Formation and Movement - Lymph formation begins when blood plasma filters out of blood capillaries into the interstitial spaces. - This fluid then drains into lymphatic capillaries and is called lymph. - The lymph is then transported back to the cardiovascular circulation via the lymphatic vessels. ### Lymphatic Organs - **Tonsils:** These lymphatic organs are located in the throat and help to protect the body from infection. There are three types of tonsils: - **Palatine Tonsils:** located on each side of the oral cavity. - **Pharyngeal Tonsils:** located near the internal opening of the nasal cavity. - **Lingual Tonsils:** located at the posterior surface of the tongue. - **Lymph Nodes:** These lymphatic organs are located throughout the body and are responsible for filtering lymph and exposing lymphocytes to antigens. - **Spleen:** This lymphatic organ is located in the abdomen and plays a key role in filtering blood, storing blood cells, and destroying old red blood cells. - **Thymus Gland:** This lymphatic organ is located in the chest and is where T cells mature before migrating to other parts of the lymphatic system. ### The Spleen - The Spleen is about the size of a clenched fist. - It filters blood. - It destroys old red blood cells. - It serves as a reservoir of blood. ### The Thymus Gland: - It helps to produce and mature lymphocytes. - It is vital for immune function, particularly during childhood. ### Overview of the Lymphatic System - This is a vast system that filters fluid from the bloodstream, transports lipids, and produces immune responses. It plays a crucial role in immune surveillance by circulating lymphocytes throughout the body. ## Immunity - **Immunity** is the ability to resist damage from foreign substances. - **Types of Immunity:** - **Innate Immunity:** **present at birth**; this type of immunity provides a generalized defense against any pathogen. It includes physical barriers, chemical mediators, and cells. - **Adaptive Immunity:** **acquired after birth**; this type of immunity is very specific. Adaptive immunity is slower than innate immunity, but it has memory. It uses lymphocytes (B and T cells) to recognize and destroy specific antigens, providing the body with a more robust and tailored immune response. ### Innate Immunity - The first line of defense against invading pathogens consists of **physical barriers**: - **Skin:** serves as a protective layer, preventing pathogen entry. - **Mucous Membranes:** line the respiratory, digestive, and urogenital tracts, trap pathogens, and secrete mucus which traps and removes pathogens. - **Chemical Mediators:** these chemicals help to kill microbes or prevent them from infecting cells - **Lysozyme:** found in tears and saliva, attacks and destroys bacterial cells. - **Mucous Membranes:** prevent pathogens from entering the body. - **Histamine:** triggers inflammation by causing vasodilation. - **Interferons:** proteins produced by virally infected cells to protect surrounding cells from viral infection. - **White Blood Cells:** these cells provide a cellular defense against microbes. - **Phagocytic Cells:** (neutrophils and macrophages) these cells engulf and destroy foreign substances. - **Eosinophils:** release chemicals that reduce inflammation. - **Basophils:** release histamine, contributing to inflammation. - **Mast Cells:** are found in tissues and release chemicals that contribute to inflammation. - **Natural Killer Cells:** destroy diseased cells by releasing chemicals that cause cell lysis. - **Inflammatory Response:** This is a response triggered by damage, inflammation, or a foreign substance. It involves chemical mediators and white blood cells to fight against infection. ### Adaptive Immunity - This type of immunity is specific and provides an immune response to a particular antigen. - Adaptive immunity is divided into two main branches: - **Antibody-Mediated Immunity:** this branch is also known as Humoral Immunity, involves the production of antibodies by B cells. - **Cell-Mediated Immunity:** this branch involves lymphocytes known as T cells. ### Terms Related to Adaptive Immunity - **Antigen:** any substance that causes an immune response, examples include viruses, bacteria, pollen. - **Self-Antigen:** molecules on the surface of cells that stimulate an immune response, but are not recognized as foreign. - **Antibody:** proteins produced by B cells in response to a specific antigen, they bind to antigens and can neutralize them or mark for destruction by other immune cells. ### Origin and Development of Lymphocytes - **Stem Cells:** these cells are produced in the red bone marrow, can give rise to all blood cells, including pre B cells and pre T cells. - **Lymphocytes:** white blood cells that are responsible for adaptive immunity. The two main types of lymphocytes are B cells and T cells. ### Lymphocytes - **B Cells:** differentiate into plasma cells that produce antibodies. - **T Cells:** they mature in the thymus gland, and are important for cell-mediated immunity. There are several types of T cells: - **Helper T Cells (TH):** activate macrophages, promote B cell function, and release cytokines. - **Cytotoxic T Cells (TC):** also known as CD8 cells, destroy virus-infected cells. - **Regulatory T Cells or Suppressor T Cells (TS):** help to suppress the immune response and prevent autoimmune reactions. - **Antigen Recognition:** lymphocytes have antigen receptors, which recognize specific antigens and trigger the immune response. These receptors are called B-cell receptors on B cells and T-cell receptors on T cells. ### The MHC Molecule - Major histocompatibility complex (MHC): proteins that are responsible for presenting antigens to T cells. There are two classes of MHC molecules. - **MHC Class I:** found on all cells, displays antigens to cytotoxic T cells. - **MHC Class II:** found on antigen-presenting cells (APCs) like macrophages and B cells, display antigens to helper T cells. ### Cytokines: - These are proteins secreted by cells to regulate other cells. They play a vital role in communication between immune cells, influencing their function and activation. #### Proliferation of Helper T Cells: 1. When an antigen-presenting cell (APC) displays an antigen on its MHC Class II molecule, a helper T cell will bind to it via its T-cell receptor. 2. The helper T cell will receive additional activation signals, called costimulation, through interaction with interleukin-1 secreted from the APC and CD4, a glycoprotein on the helper T cell. 3. Upon full activation, the helper T cell secrets interleukin-2, a cytokine that promotes the growth of helper T cells and has a role in activation of other immune cells like B cells and cytotoxic T cells. ### Proliferation of Cytotoxic T Cells: 1. When a virus-infected cell displays a viral antigen on its MHC Class I molecule, it becomes a target for cytotoxic T cells, which express CD8. 2. The T-cell receptor on the cytotoxic T cell recognizes this complex and binds to it. 3. The cytotoxic T cell receives costimulation from CD8 molecules interacting with the target cell and from interleukin-2 released from activated helper T cells. 4. This activates the cytotoxic T cell, which can then proliferate and differentiate into effector cytotoxic T lymphocytes (CTLs). 5. These CTLs are capable of destroying virus-infected cells by releasing cytotoxic granules, which directly kill target cells. ### Antibody-Mediated Immunity - **Antibodies** are proteins produced by B cells that specifically bind to and neutralize antigens. They are also called immunoglobulins, and they are effective in fighting infections caused by bacteria, viruses, and toxins. - **Effects of Antibodies:** 1. **Inactivate Antigen:** Antibodies bind to antigens and render them inactive. 2. **Bind Antigens Together:** This process called agglutination, can immobilize pathogens or clump cells together. 3. **Activate Complement Cascades:** Complement system is a group of proteins that can help in the destruction of pathogens. 4. **Initiate Release of Inflammatory Chemicals:** Antibodies can bind to mast cells, which then release chemicals that cause inflammation. 5. **Facilitate Phagocytosis:** Antibodies can coat pathogens and facilitate their ingestion by phagocytes. ### Cell-Mediated Immunity - T cells use various mechanisms to directly target and destroy cells infected with pathogens. It is especially effective against intracellular pathogens, such as bacteria living inside cells and viruses. - **Types of T Cells for Cell-Mediated Immunity:** - **Helper T Cells (TH):** play a key role in activating cytotoxic T cells, and promoting antibody production by B cells. They release cytokines (interleukin-2) that stimulate other immune cells. - **Cytotoxic T Cells (TC):** eliminate virus-infected cells and cancer cells by direct contact. They release cytotoxic granules containing substances that induce apoptosis (programmed cell death) in the target cell. - **Regulatory T Cells (TS):** help to suppress the immune response, preventing over-reaction and autoimmune diseases. They contribute to tolerance and maintain immune homeostasis. ### Types of Adaptive Immunity - **Naturally Acquired Immunity:** is gained through natural exposure to pathogens. - **Active:** develops when you are infected by a pathogen. - **Passive:** provided to a child by their mother, example colostrum or through the placenta. - **Artificially Acquired Immunity:** is gained through medical interventions. - **Active:** through vaccination, introduces weakened or inactive pathogens to the immune system. - **Passive:** through injection of antibodies from another individual, example giving antivenom, rabies immunoglobulin, or tetanus immunoglobulin. ### Ways to Acquire Adaptive Immunity - **Active Immunity:** the immune system is challenged by a genuine pathogen. - **Natural Active Immunity:** gained through natural exposure to illness. - **Artificial Active Immunity:** acquired by vaccination, which introduces a weakened form of the pathogen. - **Passive Immunity:** antibodies are transferred from one individual to another. - **Natural Passive Immunity:** example colostrum or through the placenta. - **Artificial Passive Immunity:** gained from immunoglobulin injections, which provide pre-made antibodies. This document provides an overview of the lymphatic system and immunity, covering various aspects of both innate and adaptive immunity. It describes the key components, functions, and processes involved, including cells, organs, pathways, and mechanisms.