Ch.%2021%20The%20Lymphatic%20and%20Immune%20Systems

Page 1: Overview of the Lymphatic and Immune Systems

• Chapter 21: Introduction to the lymphatic and immune systems, focusing on their structure and functions.

Page 2: Understanding Immunity

• Immune System: Composed of a diverse cell population rather than an organ system.

• Purpose: Defends the body against disease agents, primarily through the lymphatic system where it is concentrated.

Page 3: Functions of the Lymphatic System

• Fluid Recovery: Responsible for returning approximately 15% of the fluid from tissues back to the bloodstream.

• Immunity: Filters lymph fluid to remove foreign materials.

• Lipid Absorption: Specialized lymphatic vessels known as lacteals absorb dietary lipids in the gastrointestinal tract.

Page 4: Components of the Lymphatic System

• Lymph: This is the recovered fluid from tissues.

• Lymphatic Vessels: Transport lymph throughout the body.

• Lymphatic Tissues: Composed of lymphocytes and macrophage aggregates.

• Lymphatic Organs: Concentrate defense cells; vital for immune function.

Page 5: Characteristics of Lymph

• Description: A clear fluid resembling plasma.

• Origin: Formed from extracellular fluid collected into lymphatic capillaries.

• Composition: Varies depending on the body region and substances it has interacted with.

Page 6: Structure of Lymphatic Vessels

• Capillary Walls: Composed of overlapping endothelial cells.

• Features: Closed at one end and anchored to tissue by filaments. Form valve-like structures that respond to interstitial fluid pressure.

Page 7: Illustration of Lymph Flow

• Overview: Details the interactions between lymphatic capillaries, loose connective tissue, and vascular components.

Page 8: Anatomy of Lymphatic Vessels

• Layers of Larger Vessels:

  • Tunica Interna: Includes endothelium and valves.

  • Tunica Media: Contains elastic fibers and smooth muscle.

  • Tunica Externa: The thin outer layer.

Page 9: Path of Lymph Flow

• Lymphatic Capillaries: Empty into larger vessels, leading to lymphatic trunks and subsequently to two main collecting ducts.

• Ducts:

  • Right Lymphatic Duct: Drains right arm and right side of the head and thorax.

  • Thoracic Duct: Drains the rest of the body, including the cisterna chyli in the abdomen.

Page 10: Lymphatic Trunks Structure

• Detailed Anatomy: Illustrates various lymphatic trunks and their connections to collecting ducts and veins.

Page 11: Mechanisms of Lymph Flow

• Characteristics: Similar to veins but with more valves; lymph flows at lower pressures.

• Contributors to Flow: Includes smooth muscle contraction, arterial pulsation, skeletal muscle contraction, and changes in thoracic pressure.

Page 12: Types of Lymphatic Cells

• Neutrophils: Phagocytic; respond rapidly to infection.

• Lymphocytes: Include B and T cells, crucial for adaptive immunity.

  • T Cells: Mature in the thymus.

  • B Cells: Mature in bone marrow.

Page 13: Functions of Natural Killer Cells

• Role: Kill host cells infected by pathogens and cancerous cells.

• Mechanism: Release perforin to create holes in target cells and granzymes to induce apoptosis.

Page 14: Role of Macrophages

• Description: Large phagocytic cells developed from monocytes.

• Function: Act as antigen-presenting cells (APCs) by displaying fragments of antigens to T cells.

Page 15: Dendritic and Reticular Cells

• Dendritic Cells: Antigen-presenting cells located in epidermis and mucous membranes, highly mobile.

• Reticular Cells: Stationary, help form the stroma in lymphatic organs.

Page 16: Lymphatic Tissues

• Diffuse Lymphoid Tissue: Simplest form, composed of reticular connective tissue with lymphocytes and macrophages, found throughout the body.

• Lymphatic Nodules: Structures formed by masses of lymphocytes and macrophages, can be temporary or permanent (like lymph nodes).

Page 17: Primary and Secondary Lymphatic Organs

• Primary Organs: Red bone marrow and thymus; sites where T and B cells gain competence to recognize and respond to antigens.

• Secondary Organs: Include lymph nodes, tonsils, and spleen; populated with immunocompetent cells.

Page 18: Structure of Red Bone Marrow

• Function: Site of hematopoiesis and immunity; consists of soft, vascular material.

• Cell Maturation: Blood cells mature, traversing reticular and endothelial cells to enter circulation.

Page 19: Structure and Functions of Thymus

• Description: Contains a fibrous capsule and trabeculae dividing lobes; primarily populated by T lymphocytes during maturation.

• Maturation: T cells arrive via blood and migrate through the cortex to medulla for final maturation.

Page 20: Thymus Location and Changes with Age

• Location: Bilobed gland situated in the superior mediastinum.

• Age-Related Changes: Degeneration (involution) occurs with age.

Page 21: Functions of Lymph Nodes

• Quantity: Approximately 450 lymph nodes present in young adults.

• Functions: Cleanse lymph and serve as sites for T and B cell activation.

Page 22: Anatomy of Lymph Nodes

• Structure: Includes a fibrous capsule, trabeculae, stroma of reticular fibers, and parenchyma divided into cortex and medulla.

• Follicles: Contain B cells that proliferate into plasma cells.

Page 23: Responses to Antigen Challenge in Nodes

• Lymphadenitis: Enlargement and pain of lymph nodes during foreign challenges.

• Lymphadenopathy: General term for all conditions affecting lymph nodes.

• Metastasis: Spread of cancer cells to nearby lymph nodes.

Page 24: Tonsils

• Function: Guard against pathogens entering through ingestion or inhalation.

• Structure: Covered with epithelium with tonsillar crypts and part of MALT.

Page 25: Structure and Function of the Spleen

• Largest Lymphatic Organ: Contains two distinct types of tissue, red and white pulp.

• Role of Macrophages: Clear aged blood cells and pathogens from circulation.

Page 26: Peyer’s Patches

• Function: Component of MALT, consisting of lymphoid follicles within the distal small intestine and appendix.

Page 27: Overview of Immunity

• Three Lines of Defense:

  • First Line: Skin and mucous membranes.

  • Second Line: Innate defenses (e.g., leukocytes, inflammation).

  • Third Line: Adaptive immunity with memory of previous exposures.

Page 28: Interactions Between Innate and Adaptive Immunity

• Components:

  • Physical Barriers: Skin and membranes.

  • Protective Proteins and Mechanisms: Complement system, cytokines, innate leukocytes, etc.

Page 29: Characteristics of Innate Immunity

• Definition: Local, nonspecific, no memory component.

• Four Categories: Physical and chemical barriers, protective proteins, cells, and processes.

Page 30: Physical and Chemical Barriers

• Examples: Skin layers, acid mantle, mucus, cilia, and antimicrobial enzymes in bodily fluids.

Page 31: Protective Proteins in Innate Immunity

• Complement Proteins: Assist with inflammatory responses and phagocytosis; can disrupt pathogen membranes.

Page 32: Interferons as Protective Proteins

• Function: Released by infected cells to alert adjacent cells and enhance their resistance to pathogens.

Page 33: Role of Protective Cells

• Natural Killer Cells: Attack and destroy pathogens by perforation and inducing apoptosis with granzymes.

Page 34: White Blood Cell Functions

• Recruitment: Dendritic cells, macrophages, and neutrophils endocytose pathogens; basophils and eosinophils help with inflammation and response.

Page 35: Protective Processes

• Fever: Elevated body temperature enhances immune function and inhibits pathogen growth.

Page 36: Inflammation as a Defensive Response

• Characteristics: Mobilizes defenses, contains pathogens, and facilitates tissue repair.

• Cardinal Signs: Redness, swelling, heat, and pain.

Page 37: Mobilization of Defenses during Inflammation

• Process: Increased blood flow due to local hyperemia through vasodilation and increased permeability, driven by cytokines.

Page 38: Containment and Destruction of Pathogens

• Timeline: Neutrophils arrive early (within an hour) via chemotaxis to phagocytize pathogens and initiate further immune responses.

Page 39: Tissue Cleanup Post-Inflammation

• Monocyte Role: Transform into macrophages for primary cleanup and repair tasks after 8-12 hours post-injury.

Page 40: Characteristics of Adaptive Immunity

• Three Key Features: Systemic response, specificity to pathogens, and immune memory for quick responses upon re-exposure.

• Two Types: Cellular (T-lymphocytes) and Humoral (B-lymphocytes).

Page 41: Types of Immunity

• Natural Active: Development of antibodies through pathogen exposure.

• Artificial Active: Antibody production through vaccination.

• Natural Passive: Transfer of antibodies through placenta or breast milk.

• Artificial Passive: Temporary immunity from injected antibodies.

Page 42: Antigens Defined

• Definition: Any molecule capable of triggering an immune response; often complex structures unique to individuals.

• Types: Can be proteins, polysaccharides, or glycoproteins.

Page 43: Antigen-Presenting Cells (APCs)

• Role: Necessary for T-cell activation; include dendritic cells, macrophages, and B-cells, relying on MHC complex proteins for recognition of antigens.

Page 44: Types of Lymphocytes

• Categories:

  • Natural Killer (NK) Cells: For immune surveillance.

  • T Lymphocytes: Cellular immunity

  • B Lymphocytes: Humoral immunity

Page 45: Cellular Immunity Overview

• Mechanism: T-lymphocytes attack foreign or diseased cells directly, targeting pathogens within human cells inaccessible to antibodies.

• Types of T Cells: Cytotoxic, Helper, Regulatory, and Memory T cells.

Page 46: Types of T-Cells Defined

• Cytotoxic T Cells: Effectors of cellular immunity; execute attacks on infected or foreign cells.

• Helper T Cells: Support and amplify immune responses of B and T cells.

• Regulatory T Cells: Modulate immune responses to prevent overactivity.

• Memory T Cells: Retain information for rapid response to previously encountered antigens.

Page 47: T-Cell Interactions with MHC Proteins

• MHC-I Proteins: Present on nucleated cells; trigger T-cell response only for non-self antigens.

• MHC-II Proteins: Present only on APCs and required for Helper T-cell activation.

Page 48: Activation of T-Cells

• Procedure:

1. Recognition: T cells recognize antigens presented by APCs.

2. Activation: Clonal selection and response of T cells.

3. Effect: Attack pathogens and retain memory.

Page 49: Helper T-Cells Functionality

• Support Role: Coordinate responses of macrophages, B cells, and other leukocytes through cytokines.

Page 50: Humoral Immunity Explained

• Process: B-lymphocytes mediate immunity through antibodies that tag pathogens rather than directly destroy them.

• Targeted Pathogens: Effective against extracellular agents like bacteria and toxins.

Page 51: Structure of Antibodies

• Immunoglobulin (Ig): Defensive proteins comprised of two heavy chains and two light chains linked by disulfide bonds, forming the basic unit of antibodies.

Page 52: Classes of Antibodies

• IgA: Protects mucosal surfaces.

• IgD: Involved in B cell activation.

• IgE: Primarily responds to allergens.

Page 53: Additional Antibody Classes

• IgG: Predominant antibody in circulation; provides long-term protection.

• IgM: First antibody produced; effective in agglutination.

Page 54: The Humoral Immune Response Process

1. Recognition: B cells bind antigens and present them with the help of helper T cells.

2. Attack: Antibodies are produced against antigens identified.

3. Memory: Memory B cells are created for future responses.

Page 55: Mechanisms of Humoral Attack

• Neutralization: Antibodies block pathogens.

• Complement Fixation: Binding of antibodies that leads to inflammation or pathogen lysis.

Page 56: Additional Humoral Attack Mechanisms

• Agglutination: Antibody binds multiple pathogens, enhancing phagocytosis.

• Precipitation: Forms antigen-antibody complexes for elimination by the immune system.

Page 57: Memory in Humoral Immunity

• Primary Response: Initial encounter forms memory of antigen.

• Secondary Response: Faster and more robust response upon re-exposure due to memory B cells.