The Lymphatic System Study Guide PDF

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Chapter 22- The Lymphatic System Study Guide ❖ What is a pathogen? ➢ Microscopic organisms that cause diseases such as viruses, bacteria, fungi, and parasites that each attack in a specific way ❖ What is immunity? ➢ The ability to resist infection and disease ❖ What is the organization of the immune system? ➢ Blood in capillaries > interstitial fluid > hormones, nutrients, wastes, and pathogens into lymphatic capillaries > lymphatic trunk > right lymphatic duct / thoracic duct > right / left subclavian veins > cardiovascular system ❖ What is the function of a lymphoid nodule? ➢ A filter that purifies a lymph before return to venous circulation and removes debris, pathogens, and 99 percent of antigens. Areolar tissue with densely packed lymphocytes and germinal center contains dividing lymphocytes. ❖ What is the function of Mucosa-Associated Lymphoid Tissue (MALT)? ➢ Where antigen sampling occurs and immune responses are initiated. ❖ What are the 5 tonsils? ➢ Left and right palatine tonsils ➢ Pharyngeal tonsil (adenoid) ➢ Two lingual tonsils ❖ What are the function of the tonsils?

➢ A main function of tonsils is to trap germs (bacteria and viruses) which you may breathe in. Proteins called antibodies produced by the immune cells in the tonsils help to kill germs and help to prevent throat and lung infections. ❖ What is the function of the thymus? ➢ The function of the thymus is to receive immature T cells that are produced in the red bone marrow and train them into functional, mature T cells that attack only foreign cells. The thymus is divided into two thymic lobes and releases thymosin. ❖ What is the function of the spleen? ➢ Removal of abnormal blood cells and other blood components by phagocytosis ➢ Storage of iron recycled from red blood cells ➢ Initiation of immune responses by B cells and T cells ❖ What is innate immunity (nonspecific defense)? ➢ Always works the same way, against any type of invading agent, nonspecific resistance. There are 7 major categories. ❖ What do Physical Barriers do? ➢ Keeps hazardous materials outside the body. ➢ Outer layer of skin ➢ Hair ➢ Epithelium/layers of internal passageways ➢ Secretions that kill or inhibit microorganisms (sweat glands, mucus, urine, enzymes, antibodies, and stomach acid) ❖ What do Phagocytes do? ➢ Attack and remove dangerous microorganisms. ➢ Two Classes of Phagocytes:

■ Microphages- neutrophils and eosinophils, leave the bloodstream, and enter peripheral tissues to fight infections ■ Macrophages- large phagocytic cells derived from monocytes, distributed throughout the body, and make up monocyte-macrophage system ● Fixed macrophages (histiocytes)-stay in tissues or organs ● Free macrophages (wandering macrophages)-travel throughout the body ❖ What is Immune Surveillance? ➢ Constantly monitors normal tissues with natural killer cells (NK Cells) ➢ Activated NK Cells: ■ Identify and attach to abnormal cell (nonselective) ■ Golgi apparatus in NK cell forms perforin vesicles ■ Vesicles release protein called perforins (exocytosis) ■ Perforins lyse abnormal plasma membrane and also attack cancer cells and cells infected with viruses

❖ What are Interferons? ➢ Chemical messengers that trigger production of antiviral proteins in normal cells. ➢ Antiviral proteins do not kill viruses and block replication in cell.

➢ There are 3 types of Interferons: ■ Alpha-interferons= is produced by cells infected with viruses. They attract and stimulate NK cells and enhance resistance to viral infection. ■ Beta-interferons= is secreted by fibroblasts and slows inflammation in a damaged area. ■ Gamma-interferons= is secreted by T cells and NK cells and stimulates macrophage activity. ❖ What is a Complement? ➢ System of circulating proteins that assist antibodies in destruction of pathogens. ➢ Plasma contains 30 special complement (C) proteins ➢ Two pathways activate the system: ■ Classical pathway- fast method C1 binds to antibody molecule attached to antigen (bacterium) ■ Alternative pathway- slow method exposed to antigen, interact in plasma.

❖ What is an Inflammatory Response? ➢ Localized, tissue-level response that tends to limit spread of injury or infection. ➢ Symptoms: swelling, redness, heat, pain ➢ Effects: temporary repair and barrier against pathogens, retards spread of pathogens, mobilization of local, systemic defenses, and facilitation of repairs (regeneration)

➢ Products of Inflammation: ■ Necrosis- local tissue destruction in area of injury ■ Pus- mixture of debris and necrotic tissue ■ Abscess- pus accumulated in an enclosed space ❖ What is a Fever? ➢ A high body temperature above 37.2 C (99 F) that increases body metabolism, accelerates defenses, and inhabits some viruses and bacteria. ➢ Pyrogens- any material that causes the hypothalamus to raise body temperature ❖ What is an Adaptive Immunity (specific defense)? ➢ It protects against specific pathogens, depends on activities of lymphocytes, specific resistance (immunity). Develops after exposure to environmental hazards, ➢ T cells= provide cell-mediated immunity and defend against abnormal cells and pathogens inside cells ➢ B cells= provide antibody-mediated immunity and defend against antigens and pathogens in body fluids

❖ Virus Example: Antigen in Blood/Lymph > endocytosis into a normal cell > abnormal peptides in cell as a result--as the virus stimulates their creation (peptides are short chains of amino acids) > abnormal peptides inserted by cell onto plasma membrane > abnormal peptide, or “flag,” signals lymphatic cells in extracellular fluid (these “flags” are called Major Histocompatibility Complex I proteins or MHC I proteins) > specific T cells bind to the “flag” or abnormal peptide on MHC I proteins > Cytotoxic Ts/Memory Ts/Suppressor Ts have CD 8 markers (Cluster of Differentiation markers) which allow

for binding onto MHC I antigens > T cell needs to be co-stimulated by a chemical messenger to activate after binding ❖ Bacteria Example: Antigen in Blood/Lymph > engulfed and broken down by phagocyte > abnormal peptides in phagocyte as a resultbroke down components of the bacteria > abnormal peptides are presented to lymphatic cells in extracellular fluid on external surface of plasma membrane (Major Histocompatibility Complex II or MHC II proteins) > specific T cells bind to the “flag” or abnormal peptide on MHC II proteins > Helper Ts/ Memory Helper Ts have CD 4 markers (Cluster of Differentiation markers) which allow for binding onto MHC II antigens > T Helper cell needs to be co-stimulated by a chemical messenger to activate after binding > causes release of cytokines (chemical messengers) from Helper Ts ❖ What do cytokines do? ➢ Stimulate T cell division ➢ Attract and stimulate activity of cytotoxic T cells ➢ Promotes activation of B cells ❖ Exposure of B cells to antigen “sensitization” > activation by cytokines released from Helper Ts > differentiation into Memory Bs/ Plasma cells > Plasma cells release antibodies which bind to antigens...