Chapter 14: The Lymphatic System and Immunity

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Chapter 14 The Lymphatic System and Immunity
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Functions of The Lymphatic System

• Produce, maintain, and distribute lymphocytes
• Return fluid and solutes to the blood
• Distribute hormones, nutrients, and wastes from
  tissues to circulatory system
• Helps to protects us against pathogens and disease

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Organization of the Lymphatic System

• Lymphatic Vessels
• Lymph
• Thymus
• Spleen
• Lymphocytes

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4 Parts of the Lymphatic System

• Lymphatic vessels (lymphatics)
• network that carries lymph from peripheral
  tissues to the venous system
• Lymph
• a fluid similar to plasma
• does not have plasma proteins

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4 Parts of the Lymphatic System

• Lymphoid tissues and lymphoid organs
• found throughout the body
• Lymphocytes, phagocytes, and other immune system
  cells

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Lymphatic Vessels and Valves
Figure 223
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The Thoracic Duct
The Right Lymphatic Duct

• Collects lymph from
• left bronchiomediastinal trunk
• left subclavian trunk
• left jugular trunk
• Empties into left subclavian vein

• Collects lymph from
• right jugular trunk
• right subclavian trunk
• right bronchiomediastinal trunk
• Empties into right subclavian vein

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Lymphatic Ducts and the Venous System
Figure 224
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Lymphoid Tissues

• Connective tissue
• dominated by lymphocytes

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Distribution of Lymph Tissues and Nodes

• Lymph nodes
• Respiratory tract (tonsils)
• left and right palatine tonsils
• pharyngeal tonsil (adenoid)
• 2 lingual tonsils
• Along digestive and urinary tracts

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Lymph Nodes

• A filter
• purifies lymph before return to venous
  circulation
• Removes
• debris
• pathogens
• 99 of antigens

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Lymphoid Organs

• Thymus
• Lymphocytes divide in the thymus
• Mature T Cells leave the thymus
• Deteriorates after puberty
• diminishing effectiveness of immune system

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Lymphoid Organs

• Spleen
• Removes abnormal blood cells and other
  components by phagocytosis
• Stores iron recycled from RBCs
• Initiates activities by B cells and T cells in
  response to antigens in circulating blood

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Lymphocytes

• Make up 2030 of circulating leukocytes
• Lymphocytes are produced
• in lymphoid tissues (e.g., tonsils)
• lymphoid organs (e.g., spleen, thymus)
• and in red bone marrow
• Lymphocytes
• detect problems
• travel into site of injury or infection

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3 Classes of Circulating Lymphocytes

• T cells
• thymus-dependent
• B cells
• bonemarrow derived
• NK cells
• natural killer cells

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T Cells

• Make up 80 of circulating lymphocytes
• Produce cell-mediated immunity

3 Main Types Cytotoxic T Cells - Attack cells
infected by viruses Helper T Cells - Stimulate
function of T cells and B cells Suppressor T
Cells - Inhibit function of T cells and B cells
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B Cells

• Produce antibody (humoral)-mediated immunity
• Make up 1015 of circulating lymphocytes
• Differentiate into plasma cells
• Plasma Cells
• Produce and secrete antibodies (immunoglobin
  proteins)
• The binding of a specific antibody to its
  specific target antigen initiates
  antibody-mediated immunity

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Natural Killer (NK) Cells

• Provides immunological surveillance
• Also called large granular lymphocytes
• Make up 510 of circulating lymphocytes
• Attacks foreign cells, infected cells, and
  cancerous cells

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The Immune System

• All body cells and tissues involved in defense of
  the body against pathogens and the production of
  immunity
• IMMUNITY the ability of the body
• to resist disease
• Two categories of Defense Mechanisms
• Nonspecific Defenses
• Specific Defenses

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Pathogens

• Microscopic organisms that cause disease
• viruses
• bacteria
• fungi
• parasites
• Each attacks in a specific way

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Nonspecific Defenses

• Block or attack any potential infectious organism
• Cannot distinguish one attack from another

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Types of Nonspecific Resistance

• Physical barriers
• Phagocytic cells
• Immunological surveillance
• Interferons
• Complement
• Inflammation
• Fever

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The 7 Nonspecific Defense Mechanismss
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Physical Barriers

• Outer layer of skin
• Hair
• Epithelial layers of internal passageways
• Secretions that flush away materials
• sweat glands, mucus, and urine
• Secretions that kill or inhibit microorganisms
• enzymes, antibodies, and stomach acids

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2 Classes of Phagocytic Cells

• Microphages
• neutrophils and eosinophils
• Leave the bloodstream to fight infections
• Macrophages
• large phagocytic cells derived from monocytes
• May be fixed or free moving

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Immunological Surveillance

• Is carried out by natural killer (NK) cells
• Identifies, attaches, and kills (via lysis)
  abnormal cells (cancer cells, cells infected with
  viruses)

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Interferons

• Proteins (cytokines) released by activated
  lymphocytes and macrophages
• Chemical messengers released by tissue cells
• to coordinate local activities
• to act as hormones to affect whole body
• stimulate NK cells
• slow inflammation
• stimulate macrophage activity

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Complement

• Plasma contains 11 special complement (C)
  proteins
• that complement antibody action by
• Stimulation of inflammation
• Attraction of phagocytes
• Enhancement of phagocytosis by opsonization
• Destruction of target cell membranes

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Inflammation

• Also called inflammatory response
• A localized response
• Triggered by any stimulus that kills cells or
  injures tissue
• Symptoms
• Swelling (tumor)
• Redness (rubor)
• Heat (calor)
• Pain (dolor)

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3 Effects of Inflammation

• Temporary repair and barrier against pathogens
• Slows spread of pathogens into surrounding areas
• Mobilization of local and systemic defenses
• and facilitation of repairs (regeneration)

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Fever

• A maintained body temperature above 37C (99F)
• Pyrogen a substance that causes the
  hypothalamus to raise body temperature. (ie
  circulating pathogens, toxins, pyrogens released
  by active macrophages, cytokines
• Increases metabolism and cellular activities to
  stimulate repair
• gt104can cause systemic damage

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Specific and Nonspecific Defenses
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Specific Defenses

• Specific resistance (immunity)
• responds to specific antigens
• with coordinated action of T cells and B cells
• Antigens unique targets found on cell membranes
  which identify any pathogen or foreign compound
  as not self

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4 Properties of Immunity

• Specificity- Each T or B cell responds only to a
  specific antigen and ignores all others
• Versatility-The body produces many types of
  lymphocytes. Each fights a different type of
  antigen. Active lymphocyte clones itself to
  fight specific antigen.
• Memory-Some active lymphocytes (memory cells)
  stay in circulation and provide immunity
  against new exposure
• Tolerance-Immune system ignores normal antigens
  

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Forms of Immunity
Figure 2214
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Forms of Immunity

• Innate
• present at birth, genetically determined
• Acquired
• after birth
• produced after exposure to antigen

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Acquired Immunity

• Active
• antibodies develop after exposure to antigen
• Passive
• antibodies are transferred from another source

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Active Immunity

• Naturally acquired
• through environmental exposure to pathogens
• Induced
• through vaccines containing pathogens (antigens)
  or antibodies to combat infection

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Passive Immunity

• Naturally acquired
• antibodies acquired from the mother
• Induced
• by an injection of antibodies

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B Cell Sensitization and Activation
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Immune Disorders

• Autoimmune disorders
• Immunodeficiency disease
• Allergies

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Autoimmune Disorders

• A malfunction of system that recognizes and
  ignores normal antigens
• Activated B cells make autoantibodies against
  body cells
• Lupus
• Rheumatoid arthritis
• Insulin-dependent diabetes mellitus

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Immunodeficiency Diseases

• Viral infections such as HIV
• can result in AIDS
• Immunosuppressive drugs or radiation treatments
• can lead to complete immunological failure

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Allergies

• Inappropriate or excessive immune responses to
  antigens
• Allergens
• antigens that trigger allergic reactions

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4 Categories of Allergic Reactions

• Type I
• immediate hypersensitivity (allergies)
• Type II
• cytotoxic reactions (blood type incompatibility)
• Type III
• immune complex disorders (tissue damage)
• Type IV
• delayed hypersensitivity (poison oak)

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Antihistamine Drugs

• Block histamines released by MAST cells
• Can relive mild symptoms of immediate
  hypersensitivity

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Stress and the Immune Response

• Glucocorticoids
• secreted to limit immune response
• long-term secretion (chronic stress)
• inhibits immune response
• lowers resistance to disease

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Aging and the Immune Response

• Immune system deteriorates with age, increasing
  vulnerability to infections and cancer.