Anaphy Finals

• Lymphatic system


  Consists of two semi-independent parts: lymphatic vessels and lymphoid tissues and organs
• Lymphatic system functions


  • Transports escaped fluids from the cardiovascular system back to the blood
  • Plays essential roles in body defense and resistance to disease
• Lymph


  Excess tissue fluid and plasma proteins carried by lymphatic vessels
• If fluids are not picked up

  Edema occurs as fluid accumulates in tissues
• Lymphatic vessels (lymphatics)


  Pick up excess fluid (lymph) and return it to the blood
• Lymph flow in lymphatic vessels


  Lymph flows only toward the heart
• Lymph capillaries


  • Weave between tissue cells and blood capillaries
  • Walls overlap to form flaplike minivalves
  • Fluid leaks into lymph capillaries
  • Capillaries are anchored to connective tissue by filaments
  • Higher pressure on the inside closes minivalves
  • Fluid is forced along the vessel
• Lymph transport


  1. Aided by: Milking action of skeletal muscles

  2. Pressure changes in thorax during breathing

  3. Smooth muscle in walls of lymphatics
• Lymph nodes


  Filter lymph before it is returned to the blood
• Lymph nodes


  • Harmful materials that are filtered: Bacteria
  • Viruses
  • Cancer cells
  • Cell debris
• Defense cells within lymph nodes

  • Macrophages—engulf and destroy bacteria, viruses, and other foreign substances in lymph
  • Lymphocytes—respond to foreign substances in lymph
• Structure of lymph nodes

  • Most lymph nodes are kidney-shaped, less than 1 inch long, and buried in connective tissue
  • Surrounded by a capsule
  • Divided into compartments by trabeculae
  • Cortex (outer part) contains follicles—collections of lymphocytes
  • Medulla (inner part) contains phagocytic macrophages
• Flow of lymph through lymph nodes

  1. Lymph enters the convex side through afferent lymphatic vessels

  2. Lymph flows through a number of sinuses inside the node

  3. Lymph exits through efferent lymphatic vessels

  4. Because there are fewer efferent than afferent vessels, flow is slowed
• Other lymphoid organs


  • Spleen
  • Thymus
  • Tonsils
  • Peyer's patches
  • Appendix
• Spleen


  • Located on the left side of the abdomen
  • Filters and cleans blood of bacteria, viruses, debris
  • Provides a site for lymphocyte proliferation and immune surveillance
  • Destroys worn-out blood cells
  • Forms blood cells in the fetus
  • Acts as a blood reservoir
• Thymus


  • Found overlying the heart
  • Functions at peak levels only during youth
• Tonsils


  • Small masses of lymphoid tissue deep to the mucosa surrounding the pharynx (throat)
  • Trap and remove bacteria and other foreign pathogens
  • Tonsillitis results when the tonsils become congested with bacteria
• Peyer's patches


  • Found in the wall of the small intestine
  • Similar lymphoid follicles are found in the appendix
  • Macrophages capture and destroy bacteria in the intestine
• Mucosa-associated lymphoid tissue (MALT)

  • Includes Peyer's patches, tonsils, appendix
  • Acts as a sentinel to protect respiratory and digestive tracts
• Innate (nonspecific) defense system


  • Mechanisms protect against a variety of invaders
  • Responds immediately to protect body from foreign materials
• Adaptive (specific) defense system


  • Fights invaders that get past the innate system
  • Specific defense is required for each type of invader
• Immunity


  Specific resistance to disease
• Innate body defenses


  • Body surface coverings: Intact skin, Mucous membranes
  • Specialized human cells
  • Chemicals produced by the body
• Surface membrane barriers


  • Provide the first line of defense against the invasion of microorganisms
  • Protective secretions produced by these membranes: Acidic skin secretions inhibit bacterial growth, Sebum is toxic to bacteria, Mucus traps microorganisms, Gastric juices are acidic and kill pathogens, Saliva and tears contain lysozyme (enzyme that destroys bacteria)
• Internal defenses: Cells and chemicals

  • Natural killer cells and phagocytes
  • Inflammatory response
  • Chemicals that kill pathogens
  • Fever
• Natural killer (NK) cells

  • Lyse (burst) and kill cancer cells, virus-infected cells
  • Release chemicals called perforin and granzymes to degrade target cell contents
• Inflammatory response


  • Triggered when body tissues are injured
  • Four most common indicators (cardinal signs) of acute inflammation: Redness, Heat, Pain, Swelling (edema)
• Inflammatory response


  1. Damaged cells release inflammatory chemicals: Histamine, Kinin

  2. These chemicals cause: Blood vessels to dilate, Capillaries to become leaky, Phagocytes and white blood cells to move into the area (called positive chemotaxis)
• Functions of the inflammatory response

  • Prevents spread of damaging agents
  • Disposes of cell debris and pathogens through phagocytosis
  • Sets the stage for repair
• Process of the inflammatory response

  1. Neutrophils migrate to the area of inflammation by rolling along the vessel wall (following the scent of chemicals from inflammation)

  2. Neutrophils squeeze through the capillary walls by diapedesis to sites of inflammation

  3. Neutrophils gather in the precise site of tissue injury (positive chemotaxis) and consume any foreign material present
• Phagocytes


  • Cells such as neutrophils and macrophages engulf foreign material by phagocytosis
  • The phagocytic vesicle is fused with a lysosome, and enzymes digest the cell's contents
• Inflammation


  1. Inflammatory chemicals diffusing from the inflamed site act as chemotactic agents

  2. Neutrophils enter blood from bone marrow and roll along the vessel wall

  3. Positive chemotaxis

  4. Diapedesis through capillary wall

  5. Endothelium

  6. Basement membrane
• Phagocytes


  Cells such as neutrophils and macrophages engulf foreign material by phagocytosis
• Phagocytosis by a macrophage

  1. Phagocyte adheres to pathogens

  2. Phagocyte engulfs the particles, forming a phagosome

  3. Lysosome fuses with the phagocytic vesicle, forming a phagolysosome

  4. Lysosomal enzymes digest the pathogens or debris, leaving a residual body

  5. Exocytosis of the vesicle removes indigestible and residual material
• Antimicrobial proteins


  Enhance innate defenses by attacking microorganisms directly and hindering their reproduction
• Complement proteins


  A group of at least 20 plasma proteins that circulate in the plasma and are activated when they encounter and attach to cells (complement fixation)
• Activation of complement, resulting in lysis of a target cell


  1. Activated complement proteins attach to pathogen's membrane in step-by-step sequence, forming a membrane attack complex (MAC)

  2. MAC pores in the membrane allow water to rush into the cell

  3. This influx of water causes cell lysis
• Interferons


  Small proteins secreted by virus-infected cells that bind to membrane receptors on healthy cell surfaces to interfere with the ability of viruses to multiply
• Fever


  Abnormally high body temperature is a systemic response to invasion by microorganisms, caused by pyrogens secreted by white blood cells resetting the hypothalamus thermostat higher, which inhibits the release of iron and zinc needed by bacteria and increases the speed of repair processes
• Adaptive body defenses


  The body's specific defense system, or the third line of defense, involving an immune response where antibodies target and destroy antigens