Anatomy and Physiology 1e Chapter 21 PDF

Anatomy and Physiology, 1e Chapter 21: The Lymphatic and Immune System Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserv...

Anatomy and Physiology, 1e Chapter 21: The Lymphatic and Immune System Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 1 Anatomy of the Lymphatic and Immune Systems Section 21.1 Learning Objectives 21.1.1–21.1.6 Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 3  The Lymphatic and Immune Systems The lymphatic and immune systems function together Immune system protects the body from foreign invaders (e.g., bacteria) that could cause disease or death Depends on lymphatic system Lymphatic system consists of vessels, cells, and organs Carries excess fluid back to bloodstream Filters potential pathogens from blood Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 4  Functions of the Lymphatic System Drains excess interstitial fluid (IF) from tissues IF becomes lymph once it enters lymphatic system Eventually returned to bloodstream Assists in carrying out immune responses Absorbs dietary lipids/fats Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 5  Interstitial Fluid Recycling (Figure 21.1) Blood pressure causes leakage of fluid from capillaries Increases interstitial fluid (IF) Some IF is reabsorbed by capillaries, but not all Remaining IF is absorbed by lymphatics and becomes lymph Eventually returned to bloodstream Filtered by lymph nodes along the way Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 6  Application: Edema (Figure 21.2) Also known as swelling Occurs when rate of fluid flow out of capillary exceeds rate of lymph collection Interstitial fluid (IF) accumulates in tissues and leads to edema Can occur due to damage or blockage of lymphatic system Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 7  Structure of the Lymphatic System Lymphatic vessels—transport lymph Lymph originally collected by lymphatic capillaries Lymph reaches lymph nodes along the route Lymph is screened for signs of infection in lymph nodes Lymphatic organs and tissues Structures that assist in immune responses by filtering lymph and helping lymphocytes mature Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 8  Blood Versus Lymphatic Capillaries (Figure 21.4) Blood and lymphatic capillaries run next to each other Blood capillaries permit fluid movement in two directions Into and out of capillary Lymphatic capillaries only allow fluid movement into the capillary Endothelial cells overlap leading to one- way flow Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 9  Lymphatic Capillaries (Figure 21.4B) IF enters lymphatic system via lymphatic capillaries Located alongside blood capillaries One-way flow IF enters lymphatic capillaries and lymph cannot exit Lacteals = lymphatic capillaries in small intestine Used for absorption of dietary lipids Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 10  Lymphatic Vessels, Trunks, and Ducts (Figure 21.5) Lymphatic capillaries merge to form lymphatic vessels Deliver lymph to lymph nodes for filtration Contain valves to ensure one-way flow Lymphatic vessels drain into lymphatic trunks Drain large areas of lymph Lymphatic trunks drain into lymphatic ducts Return lymph to blood Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 11  Lymphatic Ducts (Figure 21.5) Return lymph to blood via subclavian veins Right lymphatic duct Drains right upper limb, right side of the head and neck, and right side of thoracic cavity Thoracic duct (also known as left lymphatic duct) Begins as cisterna chyli within abdomen Courses upward through thoracic cavity Drains left upper limb, left side of head, neck, and thorax, and all structures below diaphragm Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 12  Lymphatic Flow Lymph flows through the lymphatics in the following order: Lymphatic capillaries Lymphatic vessels Lymphatic trunks Lymphatic ducts Flow of lymph is promoted by body movements, contractions of skeletal muscles, and breathing Valves in lymphatic vessels help ensure one-way flow also Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 13  Lymph Nodes (1 of 2) (Figure 21.3) Lymphoid organs found along the path of lymph flow Located commonly in groin, armpits, neck, chest, and abdomen Filter lymph for pathogens that may cause disease Immune cells proliferate in lymph nodes during an immune response Nodes may become enlarged and tender during infection Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 16  Lymph Nodes (2 of 2) (Figure 21.6) Filter lymph for signs of infection Grouped together in various locations Afferent lymphatic vessels add lymph to lymph node Subcapsular sinus brings lymph to filtration zone Lymph flows from cortex (dividing zone) toward medulla Exits via efferent lymphatic vessels Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 17  Breakout Group Activity 1 Obtain a diagram of the lymphatic system. Practice approximating the locations of lymph node groups on group members. Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 18  Tonsils (Figure 21.7) Tonsils Unencapsulated lymphoid tissue Protect against inhaled and ingested pathogens Help develop immunity to oral pathogen Epithelium invaginates to form tonsillar crypts Material collects here and interacts with immune cells Chronic infections may lead to removal (tonsillectomy) Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 19  Mucosa-Associated Lymphoid Tissue (MALT) (Figure 21.8) Mucosa-associated lymphoid tissue (MALT) Unencapsulated lymphoid tissue Widely distributed in mucosa of GI tract, airways, breasts, and eyes Aids in immune responses to gastrointestinal pathogens and food tolerance Bronchus-associated lymphoid tissue (BALT) Found in walls of bronchi in lungs Helps protect against inhaled pathogens Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 20  Thymus (Figure 21.9) Lymphoid organ located in mediastinum above heart Site of T cell maturation Decreases in size with age Capsule divides lobes of thymus into lobules Cortex (outer region) Medulla (inner region) Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 21  Spleen (Figure 21.10) Lymphoid organ located in left upper quadrant of abdomen Recycles old red blood cells Carries out immune responses against blood-borne pathogens Stores platelets Red pulp—mainly red blood cells White pulp—mainly white blood cells Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 24 Overview of the Immune Response Section 21.2 Learning Objectives 21.2.1–21.2.4 Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 25  Anatomy of Immune Defenses Three levels of defense in immune system Barrier defenses Prevent invasion Innate defenses Activate quickly with limited responses Adaptive responses Slower, more specific response Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 26  Features of the Immune System (1 of 2) Barriers—first line of protection Prevent entry of infectious agents Innate immune response—“first responders” If infectious agents get past barriers, these factors quickly respond Adaptive immune response—requires exposure so that body can respond to presence of specific pathogens Slower response, but more specific and effective Leads to immunological memory Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 27  Features of the Immune System (2 of 2) White blood cells play a significant role Phagocytes—engulf and destroy material Lymphocytes—coordinate activities of adaptive immunity Granular cells—release chemicals that attach pathogens Phagocytic cells participate mainly in innate immunity Can also be involved in the initiation of an adaptive immune response Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 28 Barrier Defenses and the Innate Immune Response Section 21.3 Learning Objectives 21.3.1–21.3.11 Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 31  Barrier Defenses (Table 21.1) Prevent physical entry of pathogens, flush them out, or create inhospitable environment Skin Mucous membranes Associated with digestive, urinary, respiratory, and reproductive systems Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 32  Anatomy of The Skin as a Barrier Skin is the primary barrier to pathogen entry Epithelial tissue prevents bacterial growth and entry Sweat, sebum, and other secretions aid as a barrier Can be toxic to microbes Physically “flush” away microbes Lower pH Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 33  Mucosal Barriers Found lining areas of respiratory, gastrointestinal, urinary, and reproductive systems Contain epithelial tissues that provide a physical barrier Secretions from mucosal barriers provide chemical protection Stomach acid Saliva Normal flora (nonpathogenic bacteria) Lysozyme degrades bacteria Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 34  Phagocytosis Phagocytes are cells that carry out phagocytosis Macrophages Neutrophils Dendritic cells Cells ingest target microbes/organisms by forming phagosomes Phagosome binds with lysosome inside of phagocyte Digestive enzymes of lysosome breakdown and kill target microbes Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 36  Macrophages (Figure 21.11) Macrophages Ingest bacteria or debris and enzymatically break them down Fixed macrophages—remain in one location Wandering macrophages—travel through blood to location at which they are needed Assist lymphocytes by providing evidence of infection in degraded materials Dendritic cells assist lymphocytes in a similar manner Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 37  Neutrophils Phagocytic cells in bloodstream that ingest and breakdown bacteria Attracted to areas of infection by chemotaxis Leave blood and enter tissues Mainly phagocytize bacteria Unlike macrophages, neutrophils die in the process Pus—dead neutrophil debris Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 38  Natural Killer (NK) Cells Lymphocytes that can trigger apoptosis Apoptosis—programmed cell death Infected cells display different proteins Altered proteins alert natural killer cells Attack cancerous cells and cells infected by intracellular pathogens like viruses Apoptosis destroys infected cell without releasing more pathogen Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 39  Granulocytes Leukocytes that contain visible granules released when they are active Neutrophils Granules contain vasoactive mediators like histamine Eosinophils and basophils Useful during parasitic infections Contain granules with chemicals that are harmful to parasites Mast cells are only found in tissue Release histamine and prostaglandins Leads to inflammation and stimulation of nociceptors Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 40  Recognition of Pathogens Differences in innate versus adaptive recognition: Time Innate response occurs immediately or within hours; adaptive response can take days Adaptive response may require innate response for activation Specificity Adaptive response recognizes specific details of individual pathogens Innate response recognizes generic patterns of pathogen-related molecules Use pattern recognition receptors (PRR) = membrane receptors that recognize features of a pathogen or molecules released by stressed or damaged cells Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 43  Soluble Mediators of Innate Immune Response Chemical signals that lead to cellular immune responses Cytokines—signaling molecules used for cellular communication over short distances Chemokines—attract cells to needed location via chemotaxis over long distances Interferons—cytokines used by cells infected by viruses to warn neighboring cells about a virus and stop viral replication Opsonization—proteins produced that bind to pathogens and enhance phagocytosis by attracting phagocytes Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 44  Complement System (Figure 21.12) Series of proteins found in plasma that await activation Made in liver Function in a cascade Once first proteins activate, others will activate in sequence Initiates opsonization, inflammation, and cytolysis Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 45  Inflammation (Figure 21.13) Infection or tissue damage leads to release of histamine and prostaglandins Results in vasodilation and increased vascular permeability Vasodilation increases flow of blood cells and nutrients to area Increased permeability allows easier entry of cells to site of inflammation Physical signs and symptoms include redness, heat, pain, and edema Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 46  Benefits of Inflammation It is easier for leukocytes to enter tissue Pathogens killed and debris removed Clotting factors enter inflammation site to start wound repair Aids in transport of antigens to lymph nodes to initiate adaptive response Disease: chronic inflammation is not beneficial Can cause tissue destruction and fibrosis Associated with some cancers, diabetes mellitus, and arthritis Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 47  Fever An increase in core body temperature Caused by pyrogens—cytokines that trigger fever Hypothalamus releases prostaglandin E2 in response Change in blood flow dynamics and shivering increase body temperature Benefits: Slows down bacterial and viral replication Increases effectiveness of interferon Increases production of cytokines due to faster reactions Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 50 The Adaptive Immune Response Section 21.4 Learning Objectives 21.4.1–21.4.13 Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 51  Characteristics of the Adaptive Immune Response Specificity depends on recognition of antigens Molecules that body does not recognize as “self” Detected by receptors on surface of B and T lymphocytes Adaptive immune response to foreign antigens: Cellular responses—carried out by T lymphocytes (T cells) Antibody-mediated responses—carried out by antibodies Antibodies—proteins secreted by immune system Provides immunological memory Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 52  Primary Disease and Immunological Memory Primary response occurs after first exposure to a pathogen Primary disease is usually severe because it takes time for the adaptive response to occur Secondary adaptive response occurs after a subsequent exposure to same pathogen Immunological memory allows a more intense and faster response Pathogen usually eliminated before signs and symptoms occur Provide protection against repeated diseases by same pathogens Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 53  Self-Recognition Immune system must distinguish between self-antigens (molecules already present on surface of body cell) and foreign antigens (molecules on surface of a pathogen) B cell and T cell maturation requires recognition and tolerance of self- antigens Cells must recognize self-antigens and not initiate an immune response to them B and T cells that persists and respond to self-antigens can cause autoimmune diseases Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 54  T Cell-Mediated Immune Responses (Figure 21.14) T cells control many immune responses directly Also influence B cell responses T cells recognize antigens using a T cell receptor Contains antigen binding site Each T cell receptor is unique and can only bind one type of antigen Each T cell only has one type of T cell receptor T cells only recognize one type of antigen Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 55  Antigens A large antigen may contain several antigenic determinants Smaller regions of an antigen that can bind to a receptor and initiate an immune response T cells do not recognize free antigens Require antigen-presenting cells (APCs) to process and present antigens Dendritic cells, macrophages, and B cells Phagocytize antigen, break it into smaller units, and present it to T cells using major histocompatibility complex (MHC) molecules MHC molecules are inserted into APC membrane Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 56  Antigen Processing and Presentation Using MHC Molecules (1 of 2) (Figure Two types of MHC molecules 21.15) MHC class I molecules are made by every nucleated cell of the body Body cells provide information about internal environment by displaying internal antigens Alerts immune system to the presence of intracellular foreign antigens Used to attract cytotoxic T cells Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 57  Antigen Processing and Presentation Using MHC Molecules (2 of 2) (Figure 21.15) MHC-II surface molecules are only made by APCs Antigen presenting cells (APCs) phagocytize antigens and break them down Present antigens using MHC-II molecules Alerts immune system to presence of extracellular foreign antigens Used to attract helper T cells Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 58  T Cell Development and Differentiation T cells are produced in red bone marrow but mature in thymus Through genetic recombination, different T cell receptors can be produced T cells that recognize self-antigens are eliminated through T cell tolerance During maturation, T cells are exposed to every possible self- antigen T cells that react to self-antigens are eliminated Only about 2% of T cells that enter thymus fully mature T cells that survive are self-tolerant and immunocompetent Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 59  Mechanisms of T Cell Mediated Immune Responses (Figure 21.16) Mature T cells activate by recognizing foreign antigens presented by MHC molecules Activated T cells undergo clonal selection and begin clonal expansion Cells divide to produce copies Some clones become effector T cells Actively fight infection Others become memory T cells that provide long term immunity Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 60  Cellular Basis of Immunological Memory Memory T cells are created during clonal expansion Cells do not respond during first exposure (primary disease) yet are long-lived and will respond to subsequent pathogen exposure Memory cells allow body to react quickly if secondary infection should occur Memory cells will quickly enter clonal expansion within hours Large numbers of effector cells are created and overwhelm pathogen Signs and symptoms may not be experienced upon second exposure due to intense response of adaptive immune system Provides long-term immunity Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 61  T Cell Types (Figure 21.17) Helper T Cells—CD4 protein on surface Recognize antigens presented by MHC-II Cytotoxic T Cells—CD8 protein on surface Recognize antigens presented by MHC-I Regulatory T Cells—turn off immune response after infection is eliminated Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 62  Functions of Helper and Cytotoxic T Cells (Figure 21.18) Helper T Cells—CD4 protein on cell surface Secrete cytokines to enhance adaptive immune response Recognize antigens presented by MHC- II Cytotoxic T Cells—CD8 protein on cell surface Kill target cells by inducing apoptosis Recognize antigens presented by MHC-I Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 63  B Cells (Figure 21.19) Some B cells develop into memory cells, which provide long-term immunity to specific antigens Active B cells mature into plasma cells that secrete antibodies Antibodies = proteins that are produced by B cells Travel in blood and cause immune responses Can cause cells to agglutinate or clump together Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 66  B Cell Functions B cell response requires B cells to recognize antigen first Each B cell receptor recognizes a single antigen B cells do not require antigen-presenting cells (APCs) to recognize specific antigens B cells can recognize unprocessed antigens Do not require MHC molecules B cells require cytokines from helper T cells to become fully activated Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 67  B Cell Differentiation and Activation B cells are made and mature in red bone marrow B cells that recognize self-antigens are destroyed B cell activation requires antigen recognition by B cell receptor with the support of helper T cells Active B cells mature into plasma cells Secrete antibodies that bind to antigens and cause immune response Some B cells differentiate into memory cells for long-term immunity Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 68  Clonal Expansion of B Cells (Figure 21.24) Active B cells undergo clonal expansion just like T cells Some clones become effector (plasma) cells that will secrete antibodies Others become memory cells Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 69  Memory Responses (Figure 21.20) Initial exposure to a specific pathogen (primary response) takes longer to activate the adaptive immune cells Secondary exposure to the same pathogen is faster and more intense Due to presence of memory cells that already recognize foreign antigen Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 70  Antibody Structure (Figure 21.21) Have an overall Y-shape Consists of four amino acid chains and associated carbohydrates Two heavy chains and two light chains Antigen-binding sites contain components from heavy and light chains Fc region is composed on heavy chains only Immune cells can bind Fc region leading to phagocytosis of pathogen Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 71  Antibody Classes (1 of 2) (Figure 21.23) Antibodies are also known as immunoglobulins (Ig) and divided into 5 classes: 1. IgM—first antibody produced during primary immune response Large pentamer with multiple antigen-binding sites useful during early response Class switching allows plasma cells to switch from IgM to other classes 2. IgG—most abundant class Major antibody of late primary and secondary responses Crosses placental barrier to protect fetus Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 72  Antibody Classes (2 of 2) 3. IgA—dimer consisting of two antibodies joined together Found in bodily fluids like mucus, saliva, breast milk, and tears Coats and neutralizes pathogens within mucous membranes, preventing entry into a body cell Can be passed from mother to infant by breastfeeding to protect newborns 4. IgD—found on B cells 5. IgE—trigger allergic reactions Can activate mast cells Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 73 Antibody Classes (3 of 3) (Figure 21.22) Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 74  Active and Passive Immunity (Table 21.2) Active immunity—acquired when adaptive immune response is fully carried out Passive immunity—is gained without adaptive immune response occurring Natural immunity—occurs without man- made intervention Artificial immunity—requires man-made products or intervention Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 78  Responses to Different Pathogens (Figure 21.25) Immune system can recognize and respond to diverse pathogens Bacteria and fungi – targeted by antibodies, neutrophils, and macrophages Viruses – targeted by NK cells, interferons, and cytotoxic T cells Worm parasites targeted by mucosal immune response, IgE-mediated allergy and asthma, and eosinophils Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 79  Summary By the end of this chapter, you should be able to: Describe the flow of lymph through the lymphatic system. Identify lymphatic organs and tissues. Discuss the functions of the lymphatic organs and tissues. Discuss the innate immune response. Discuss the adaptive immune response. Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 80