HS 130 Anatomy & Physiology II Unit 3 Seminar Chapter 13 The Lymphatic System And Immunity

Questions, Problems, Concerns

The Lymphatic System Functions of the lymphatic system  Allows exchange of substances, such as excess fluid and protein molecules, that cannot occur in the capillary beds  Filters out harmful substances from the lymph before returning it to the blood  Acts as sewer system of the body What is the role of lymph nodes in the spread of cancer? What role do tonsils play in preventing the spread of infection to the lower respiratory tract?

Lymph—fluid in the tissue spaces that carries protein molecules and other substances back to the blood Lymphatic vessels—permit only one-way movement of lymph Lymphatic capillaries—tiny blind-ended tubes distributed in tissue spaces Microscopic in size Sheets consisting of one cell layer of simple squamous epithelium Poor “fit” between adjacent cells results in porous walls Called lacteals in the intestinal wall (fat transportation from food to bloodstream) Right lymphatic duct Drains lymph from the right upper extremity and right side of head, neck, and upper torso Thoracic duct Largest lymphatic vessel Has an enlarged pouch along its course, called cisterna chyli Drains lymph from about three-fourths of the body The Lymphatic System

What happens to fluid from blood plasma that is not reabsorbed by blood vessels?

Which lymphatic duct drains most of the body? What is the function of the cisterna chyli? What are lacteals?

Lymph nodes Filter lymph Located in clusters along the pathway of lymphatic vessels Functions include defense and WBC formation Flow of lymph: to node via several afferent lymph vessels drained from node by a single efferent lymph vessel The Lymphatic System

What is this diagram showing?

Thymus: Lymphoid tissue organ located in mediastinum  Total weight of 35 to 40 g (a little more than an ounce)  Plays a vital and central role in immunity  Produces T lymphocytes, or T cells  Secretes hormones called thymosins  In adults, lymphoid tissue is largely replaced by fat and connective tissue in the process called involution The Lymphatic System What would you expect the course of therapy to be if a baby were born without a thymus gland?

Tonsils  Composed of three masses of lymphoid tissue around the openings of the mouth and throat  Palatine tonsils (“the tonsils”)  Pharyngeal tonsils (adenoids)  Lingual tonsils  Subject to chronic infection  Enlargement of pharyngeal tonsils may impair breathing The Lymphatic System Why would you try to avoid removal of the tonsils if at all possible?

Spleen  Largest lymphoid organ in body  Located in upper left quadrant of abdomen  Often injured by trauma to abdomen  Surgical removal called splenectomy  Functions include phagocytosis of bacteria and old RBCs  acts as a blood reservoir The Lymphatic System

Often after the surgical removal of a breast, lymph nodes, and lymphatic vessels — especially those in the upper arm — swelling occurs. What is the physiological reason that swelling takes place? Some surgical treatments for breast cancer involve removal of lymph nodes in the axillary region. Why might this have a therapeutic effect in some cases?

Diseases of the lymphatic system: Lymphangitis Lymphedema Elephantiasis Lymphoma Tonsillitis Splenomegaly

Functions of the immune system  Protects the body from pathologic bacteria, foreign tissue cells, and cancerous cells  Made up of specialized cells and molecules The Immune System

Nonspecific immunity  Skin: Mechanical barrier to bacteria and other harmful agents  Tears and mucus: Wash eyes and trap and kill bacteria  Inflammation  Attracts immune cells to site of injury, increases local blood flow, increases vascular permeability  Promotes movement of WBCs to site of injury or infection The Immune System

Inflammatory Response  Inflammation is a generalized response to an invader, such as bacteria that are causing tissue damage  This triggers release of factors from immune cells  The presence of immune factors attracts WBCs  Factors also cause increased blood flow (site becomes warm and reddened) and increased vascular permeability (site swells with associated discomfort)  These immune factor-mediated changes help phagocytic WBCs reach the site and enter the affected tissue The Immune System

Specific immunity Also called adaptive immunity because of the ability of the body to recognize, respond to, and remember harmful substances or bacteria Types of specific immunity Natural immunity—exposure to causative agent is not deliberate Active—active disease produces immunity Passive—immunity passes from mother to fetus through placenta or from mother to child through mother’s milk Artificial immunity—exposure to causative agent is deliberate Active—vaccination results in immunity Passive—protective material developed in another individual’s immune system and given to previously nonimmune individual The Immune System

Antibodies: Protein compounds with specific combining sites  Combining sites attach antibodies to specific antigens, forming an antigen–antibody complex  Inactivation of foreign protein in this way is called humoral or antibody-mediated immunity  Antigen–antibody complexes have various modes of action  Neutralize toxins  Clump or agglutinate enemy cells  Promote phagocytosis The Immune System Molecules

Complement Proteins  Group of at least 14 proteins normally present in blood in an inactive state  Complement fixation  Important mechanism of action for antibodies  Causes cell lysis by permitting entry of water through a defect created in the plasma membrane

Phagocytes: Ingest and destroy foreign cells or other harmful substances via phagocytosis  Types  Neutrophils  Monocytes  Macrophages o Kupffer’s cells o Dust cells The Immune System Molecules Where do phagocytes and lymphocytes originate?

Lymphocytes  Most numerous of immune system cells  Development of B cells  Primitive stem cells migrate from bone marrow and go through two stages of development The Immune System Molecules

Development of B Cells  Stage 1  Stem cells develop into immature B cells o Immature B cells are small lymphocytes; each synthesizes highly specific antibody molecules in their plasma membranes  Migrate via the bloodstream chiefly to lymph nodes  Become seed cells in the lymph nodes  Undergo mitosis to make clones of themselves containing their specific antibody The Immune System Molecules

Development of B Cells  Stage 2  Immature B cell develops into activated B cell if it comes in contact with its specific antigen  B cell is activated by antigens binding to its surface antibodies  Activated B cell divides repeatedly, forming two clones of cells: o Plasma cells o Memory cells

Slide 31

Function of B Cells  Humoral immunity  Activated B cells develop into plasma cells  Plasma cells secrete antibodies into the blood  Circulating antibodies produce humoral immunity

Development of T Cells  Stage 1  Stem cells from bone marrow migrate to thymus gland  Stem cells develop into T cells several months before and after birth  T cells have protein molecules on their cytoplasmic membrane shaped to bind to only one kind of antigen  T cells migrate from thymus chiefly to lymph nodes, liver, and spleen  Stage 2  Occurs only if a specific antigen binds to T cells’ surface proteins  T cells develop into sensitized T cells

Functions of T Cells  Provide cell-mediated immunity  Kill invading cells directly by releasing a substance that poisons cells  Release chemicals that attract and activate macrophages to kill cells by phagocytosis What happens when T-cell function is impaired?

Humoral immunity  Immunity conferred by the action of antibodies  Activated B cells  plasma cells and memory cells Cell-mediated immunity  Immunity conferred by the action of cells  Sensitized T cells  Kill invading cells directly by releasing lymphotoxin or releasing lymphokines that attract and activate macrophages to kill cells by phagocytosis Humoral vs Cell-mediated Immunity

Questions?? Remember you can or IM any questions or concerns to me Thanks for attending!! I’ll “see” everyone on the discussion boards!