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:
Recognition: T cells recognize antigens presented by APCs.
Activation: Clonal selection and response of T cells.
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
Recognition: B cells bind antigens and present them with the help of helper T cells.
Attack: Antibodies are produced against antigens identified.
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.