chapter 12

Chapter 12: Lymphatic System/Immunity

1.     Lymphatic system

a.    Two independent parts

                                          i.    Lymphatic vessels

                                        ii.    Lymphoid tissues and organs

b.    Lymphatic system functions

                                          i.    Transports escaped fluids back to the blood

                                        ii.    Plays essential roles in immunity

2.    Lymphatic characteristics

a.    Lymph-excess tissue fluid carried by lymphatic vessels

b.    Properties of lymphatic vessels

                                          i.    One way system toward the heart

                                        ii.    No pump

                                       iii.    Lymph moves toward the heart

                                       iv.    Milking action of skeletal muscle

                                         v.    Rhythmic contractions of smooth muscle in vessel walls

3.    Lymphatic vessels

a.    Lymphatic capillaries

                                          i.    Walls overlap to form flap like minivalves

                                        ii.    Fluid leaks into lymph capillaries

                                       iii.    Capillaries anchored to connective tissue by filalements

                                       iv.    Higher pressure on the inside closes minivalves

                                         v.    Fluid forced along the vessel

b.    Lymphatic collecting vessels (like veins)

                                          i.    Collect lymph from lymph capillaries

                                        ii.    Carry lymph to and away from lymph nodes

                                       iii.    Return fluid to circulatory veins near the heart

1.     Right lymphatic duct

2.    Thoracic duct

4.    Lymph: contains harmful materials that enter lymph vessels

a.    Bacteria

b.    Viruses

c.    Cancer cells

d.    Cell debris

5.    Lymph nodes

a.    Filter lymph before it is returned to the blood

b.    Defense cells within lymph nodes:

c.    Macrophages-engulf and destroy foreign substances

d.    Lymphocytes- provide immune response to antigens

6.    Other lymphoid organs

a.    Spleen

b.    Thymus-most active through early childhood

c.    Tonsils

d.    Peyer’s patches- in intestinal walls

7.    Lines of defense

a.    First line = skin and mucous membranes

                                          i.    Physical barrier to foreign materials

                                        ii.    Protective secretions

1.     pH of skin is acidic to inhibit bacterial growth

2.    sebum(oil) is toxic to bacteria

3.    vaginal secretions are very acidic

b.    Second line =

                                          i.    Phagocytes-cells that eat mostly bacteria

                                        ii.    Natural killer cells-contain toxic chemicals

                                       iii.    Inflammatory response

1.     Redness

2.    Heat

3.    Swelling

4.    Pain

c.    Third line =

                                          i.    Immune response= immune system’s response to a threat

                                        ii.    Immunology= study of immunity

                                       iii.    Antibodies= proteins that protect from pathogens, attach antigen molecules

                                       iv.    Three aspects of adaptive defense

1.     Antigen specific-recognizes and acts against particular foreign substances

2.    Systemic-not restricted to the initial infection site

3.    Memory-recognizes and mount a stronger attack on previously encountered pathogens

                                         v.    Types

1.     Humoral = antibody-mediated immunity

a.    Provided by antibodies present in body fluids

2.    Cellular immunity= cell-mediated immunity

a.    Targets: virus-infected cells, cancer cells, and cells of foreign grafts