Chapter 24, f 09


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  • NK cells tend to have CD16 receptors.
  • Chapter 24, f 09

    1. 1. Human Anatomy, Second Edition McKinley & O'Loughlin Chapter 24 Lecture Outline: Lymphatic System 24-
    2. 2. Lymphatic System <ul><li>Assists the cardiovascular system by transporting excess interstitial fluid ( lymph ) through lymphatic vessels. </li></ul><ul><li>Filters lymph and checks for foreign or pathologic material, such as cancer cells and bacteria. </li></ul><ul><li>Contains certain cells that initiate an immune response to abnormal materials and perform other functions essential to homeostasis and survival. </li></ul><ul><li>Without the primary immune response by the lymphatic system, the body would be unable to fight infection and keep itself healthy. </li></ul>24-
    3. 3. Functions of the Lymphatic System <ul><li>Fluid and nutrient transport, lymphocyte development, and the immune response. </li></ul><ul><li>Reabsorbs excess interstitial fluid and returns it to the venous circulation. </li></ul><ul><li>Transports dietary lipids. </li></ul>24-
    4. 4. Immune Response <ul><li>Immune defenses are specific defenses </li></ul><ul><li>B cells can become plasma cells that produce soluble proteins called antibodies. </li></ul><ul><ul><li>bind to and immobilize the foreign or abnormal agent, thus damaging it or identifying it to other elements of the immune system </li></ul></ul><ul><li>T cells can attack and destroy the antigen directly. </li></ul><ul><li>Other B and T cells become memory cells , which </li></ul><ul><ul><li>remember the past antigen encounters and initiate an even faster and more powerful response should the same antigen appear again </li></ul></ul>24-
    5. 5.
    6. 6. Lymph and Lymph Vessels 24-
    7. 7. Lymphatic Capillaries <ul><li>The lymphatic network begins with microscopic vessels called lymphatic capillaries in the tissues. </li></ul><ul><ul><li>closed-ended tubes found in most blood capillary networks ( one way system ) </li></ul></ul><ul><ul><li>similar to a blood capillary in that its wall is an endothelium </li></ul></ul><ul><ul><li>but tend to be larger in diameter, lack a basement membrane, and have overlapping endothelial cells </li></ul></ul><ul><ul><li>anchoring filaments help hold these endothelial cells to the nearby tissues </li></ul></ul><ul><ul><li>structure acts as one way valves </li></ul></ul>24-
    8. 8.
    9. 9. Lacteals <ul><li>The small intestine contains special types of lymphatic capillaries called lacteals. </li></ul><ul><li>Lacteals pick up not only interstitial fluid, but also dietary lipids and lipid-soluble vitamins. </li></ul><ul><li>The lymph of this area has a milky color due to the lipid and is called chyle . </li></ul>24-
    10. 10. Lymphatic Vessels <ul><li>Lymphatic capillaries merge to form larger lymphatic vessels </li></ul><ul><ul><li>resemble small veins and are derived from veins. </li></ul></ul><ul><ul><li>both contain three tunics and both have valves </li></ul></ul><ul><ul><li>But, lymph vessel walls are thinner and have more valves </li></ul></ul><ul><li>Most lymph passes through several nodes. </li></ul><ul><li>Afferent lymphatic vessels bring lymph to a lymph node where it is examined for foreign or pathogenic material. </li></ul><ul><li>Once filtered, the lymph exits the lymph node via efferent lymphatic vessels. </li></ul><ul><li>There are less efferent than afferent vessels so the lymph slows down as it goes through the lymph node. </li></ul><ul><li>Lymph nodes are often found in clusters. </li></ul>24-
    11. 11. Lymphatic Vessels <ul><li>Lymphatic vessels merge to form </li></ul><ul><li>Collecting vessels and then </li></ul><ul><li>Trunks and then the </li></ul><ul><li>Right lymphatic duct and left lymphatic duct (thoracic duct) which empty into the </li></ul><ul><li>Subclavian veins near the entrance of the internal jugular veins </li></ul><ul><li>Lymph is collected from the periphery all over except in the CNS </li></ul>24-
    12. 12. Movement of Lymph <ul><li>Skeletal muscle pump and valves </li></ul><ul><li>Respiratory pump </li></ul><ul><li>Smooth muscle in the lymph vessels </li></ul><ul><li>Arteries push on the nearby lymphatic vessels </li></ul>24-
    13. 13.
    14. 14.
    15. 15.
    16. 16. Lymphedema <ul><li>Accumulation of interstitial fluid from blockage of drainage </li></ul><ul><li>Area swells, is painful, may interfere with wound healing as it becomes a growth medium for bacteria </li></ul><ul><li>Most cases are obstructive </li></ul><ul><ul><li>Surgery </li></ul></ul><ul><ul><li>Spread of malignant tumors </li></ul></ul><ul><ul><li>Radiation therapy </li></ul></ul><ul><ul><li>Trauma or infections of the lymph vessels </li></ul></ul><ul><li>Parasitic filarial worm infection in Southeast Asia and Africa (in extreme cases, elephantiasis) </li></ul><ul><li>No cure but it can be controlled (our textbook) </li></ul><ul><li>Lymph vessels can regrow even through scar tissue (Marieb) </li></ul>24-
    17. 17. Lymphatic (Lymphoid) Cells <ul><li>Located in both the lymphatic system and the cardiovascular system. </li></ul><ul><li>Work together to elicit an immune response. </li></ul><ul><li>Types of lymphatic cells are: </li></ul><ul><ul><li>macrophages - monocytes that have migrated into the lymphatic system structures from the bloodstream, phagocytose foreign substances. </li></ul></ul><ul><ul><li>epithelial cells - special epithelial cells called nurse cells are found in the thymus, where they secrete thymic hormones. </li></ul></ul><ul><ul><li>dendritic cells - found in the lymphatic nodules of a lymph node. They internalize antigens from the lymph and present them to other lymphatic cells. </li></ul></ul><ul><ul><li>lymphocytes - the most numerous cells in the lymphatic system. </li></ul></ul>24-
    18. 18. Types and Functions of Lymphocytes <ul><li>T-lymphocytes (T-cells), specific. </li></ul><ul><li>B-lymphocytes (B-cells), specific. </li></ul><ul><li>NK (natural killer) cells, not specific. </li></ul><ul><li>Migrate through the lymphatic tissues and monitor them for the presence of antigens. </li></ul><ul><li>Most lymphocytes are in the lymphoid organs and tissues (1 kg)! Macrophages tend to be fixed, but lymphocytes, esp. T-cells, roam a lot. </li></ul><ul><li>Identified according to the tissue or organ where they mature: </li></ul><ul><ul><li>T -lymphocytes mature in the Thymus </li></ul></ul><ul><ul><li>B -lymphocytes mature in the Bone marrow </li></ul></ul>24-
    19. 19. T-lymphocytes (T-cells) <ul><li>About 70–85% of lymphocytes. </li></ul><ul><li>Plasma membrane contains a coreceptor that can recognize a particular antigen. </li></ul><ul><li>There are several types of T-lymphocytes, each with a particular kind of coreceptor. </li></ul><ul><ul><li>cytotoxic T-lymphocytes - cell mediated immunity. Kill virus-infected, cancer, or foreign graft cells. Bind then inject perforin leading to lysis. May also act indirectly. </li></ul></ul><ul><ul><li>helper T-lymphocytes –regulatory: managers of the immune system, the T and B lymphocytes. A target of the HIV virus. </li></ul></ul><ul><ul><li>suppressor T-lymphocytes – regulatory: inhibit T and B lymphocytes when the immune response is winding down </li></ul></ul>24-
    20. 20.
    21. 21. B-lymphocytes (B-cells) <ul><li>About 15–30% of the lymphocytes. </li></ul><ul><li>Become plasma cells , basically antibody producing factories. </li></ul><ul><li>Contain antigen receptors that respond to one particular antigen and cause the production of immunoglobulins (Ig), or antibodies, that respond to that particular antigen. </li></ul>24-
    22. 22. Vaccines <ul><li>Some vaccines introduce milder or dead forms of an antigen. </li></ul><ul><li>The second response is faster and stronger than the initial response. </li></ul><ul><li>The body can fight and eliminate the illness before any symptoms ever develop. </li></ul><ul><li>Depending upon the life span of the particular memory B-lymphocytes: </li></ul><ul><ul><li>vaccine may provide lifelong immunity, or </li></ul></ul><ul><ul><li>periodic booster shots may be needed </li></ul></ul>24-
    23. 23.
    24. 24. NK (Natural Killer) Cells <ul><li>The remaining small percentage of lymphocytes. </li></ul><ul><li>NK cells can kill a wide variety of infected cells and some cancerous cells. </li></ul><ul><li>Involved in “immunological surveillance.” </li></ul>24-
    25. 25.
    26. 26. Lymphatic Structures <ul><li>Primary lymphatic organs </li></ul><ul><ul><li>Red bone marrow -> B-cells and pre-T-cells </li></ul></ul><ul><ul><li>Pre-T-cells migrate to the thymus gland -> T-cells </li></ul></ul><ul><li>Secondary lymphatic organs and tissues </li></ul><ul><ul><li>Organs </li></ul></ul><ul><ul><ul><li>Lymph nodes </li></ul></ul></ul><ul><ul><ul><li>Spleen </li></ul></ul></ul><ul><ul><li>Tissue </li></ul></ul><ul><ul><ul><li>Lymphatic nodules in mucous membranes </li></ul></ul></ul>24-
    27. 27. Lymphatic Nodules <ul><li>Oval clusters of lymphatic cells with some extracellular matrix but no capsule. </li></ul><ul><li>Contain proliferating B-lymphocytes and some macrophages. </li></ul><ul><li>T-lymphocytes are located outside the germinal center. </li></ul><ul><li>Filter and attack antigens. </li></ul><ul><li>In some areas of the body, many lymphatic nodules group together to form larger structures, mucosa-associated lymphatic tissue (MALT) </li></ul><ul><ul><li>MALT detect antigens and initiate an immune response </li></ul></ul><ul><ul><li>tonsils ring the pharynx </li></ul></ul><ul><ul><li>Peyer patches are very prominent in the mucosa of the small intestine, primarily in the ileum </li></ul></ul><ul><ul><li>also prevalent in the appendix </li></ul></ul>24-
    28. 28. Tonsils <ul><li>Have T- and B-cells </li></ul><ul><li>Consist of multiple germinal centers and have invaginated outer edges called crypts. </li></ul><ul><ul><li>crypts help trap material and facilitate its identification by lymphocytes </li></ul></ul><ul><li>Several groups of tonsils form a protective ring around the pharynx. They may get inflamed. </li></ul><ul><ul><li>pharyngeal tonsils (or adenoids) are in the posterior wall of the nasopharynx </li></ul></ul><ul><ul><li>palatine tonsils are in the posterolateral region of the oral cavity (if recurrent infections, tonsillectomy removes these) </li></ul></ul><ul><ul><li>lingual tonsils are along the posterior one-third of the tongue (may also be removed in a tonsillectomy) </li></ul></ul>24-
    29. 29.
    30. 30. Lymphatic Organs <ul><li>Consist of lymphatic cells and extracellular matrix, and are completely surrounded by a connective tissue capsule. </li></ul><ul><ul><li>thymus </li></ul></ul><ul><ul><li>lymph nodes </li></ul></ul><ul><ul><li>spleen </li></ul></ul>24-
    31. 31. Thymus <ul><li>A bilobed organ located in the anterior mediastinum </li></ul><ul><li>Secretes hormones concerned with lymphocyte activity </li></ul><ul><li>Major site for the multiplication, differentiation, and maturation of T-lymphocytes, no B-cells or reticular fibers. </li></ul><ul><li>Important in immunity, but doesn’t directly fight. There is a blood-thymic barrier. </li></ul><ul><li>In infants and young children, it is quite large and extends into the superior mediastinum as well </li></ul><ul><li>Grows until puberty and its maximum weight of 30-50 grams </li></ul><ul><li>Cells of the thymus regress, eventually replaced by adipose </li></ul><ul><li>In adults, it atrophies and becomes almost nonfunctional </li></ul><ul><li>Most T-cells arise before puberty, but some mature throughout life. </li></ul>24-
    32. 32.
    33. 33. Lymph Nodes <ul><li>Small, round or oval structures located along the pathways of lymph vessels. </li></ul><ul><li>Range in length from 1 to 25 millimeters, and typically are found in clusters that receive lymph from many body regions. </li></ul><ul><ul><li>axillary lymph nodes receive lymph from the breast, axilla, and upper limb (breast cancer may metastasize through axillary nodes which enlarge and become hard, but not tender) </li></ul></ul><ul><ul><li>inguinal lymph nodes , receive lymph from the lower limb and pelvis </li></ul></ul><ul><ul><li>cervical lymph nodes receive lymph from the head and neck </li></ul></ul><ul><li>Also found individually throughout the body tissues. </li></ul><ul><li>Reticular fibers filter and trap foreign substances that are destroyed by macrophages, T-cells, and plasma cells. </li></ul><ul><li>Cor t ex (except for the medulla) has T -cells. </li></ul><ul><li>M edulla has m acrophages. </li></ul><ul><li>Germinal centers have B-cells that can become plasma cells. </li></ul>24-
    34. 34.
    35. 35.
    36. 36. Spleen <ul><li>Largest lymphatic organ in the body. </li></ul><ul><li>Located in the upper left quadrant of the abdomen, inferior to the diaphragm and posterior to ribs 9–11. </li></ul><ul><li>Deep red organ lies lateral to the left kidney and posterolateral to the stomach. </li></ul><ul><li>It is retroperitoneal. </li></ul><ul><li>Can vary considerably in size and weight, but typically is about 12 centimeters long and 7 centimeters wide. </li></ul>24-
    37. 37.
    38. 38.
    39. 39.
    40. 40.
    41. 41. Functions of the Spleen <ul><li>Initiates an immune response when antigens are found in the blood (a white pulp function). </li></ul><ul><li>Serves as a reservoir for erythrocytes and platelets (red pulp function). </li></ul><ul><li>Phagocytizes old, defective erythrocytes and platelets (red pulp function). </li></ul><ul><li>Phagocytizes bacteria and other foreign materials. </li></ul><ul><li>Not a lymph filter. </li></ul><ul><li>RBC formation in the fetus. </li></ul><ul><li>If damaged, may have to be removed. The liver and bone marrow take over its functions, but may need antibiotics prophylactically. </li></ul>24-
    42. 42. Lymphoma <ul><li>A malignant neoplasm that develops from lymphatic structures </li></ul><ul><li>May present as a nontender, enlarged lymph node esp. in the neck or axillary region. May be other symptoms. </li></ul><ul><li>Hodgkin Lymphoma </li></ul><ul><ul><li>Characterized by Reed-Sternberg cell </li></ul></ul><ul><ul><li>Affects young adults and people over 60. </li></ul></ul><ul><ul><li>It arises in a lymph node and travels to nearby lymph nodes. </li></ul></ul><ul><ul><li>Curable if caught early. </li></ul></ul><ul><li>Non-Hodgkin Lymphoma </li></ul><ul><ul><li>More common </li></ul></ul><ul><ul><li>Usually develop in lymphatic structures from abnormal B-cells and less commonly in T-cells </li></ul></ul><ul><ul><li>Varies and, therefore, treatments vary. </li></ul></ul>24-
    43. 43. Aging and the Lymphatic System <ul><li>The thymus is no longer able to mature and differentiate T-lymphocytes. </li></ul><ul><li>New T-lymphocytes can be produced only by replication (mitosis). </li></ul><ul><li>Ability to provide immunity and fight disease decreases. </li></ul><ul><li>Helper T-lymphocytes do not respond to antigens as well, and do not always reproduce rapidly. </li></ul><ul><li>Fewer B-lymphocytes and other kinds of T-lymphocytes. </li></ul><ul><li>The body’s ability to acquire immunity and resist infection decreases, making elderly people more susceptible to illnesses and more likely to become sicker. </li></ul><ul><li>Faltering immune system makes the elderly more prone to developing cancers. </li></ul>24-
    44. 44. HIV and AIDS <ul><li>Acquired immunodeficiency syndrome </li></ul><ul><ul><li>Life-threatening </li></ul></ul><ul><ul><li>Targets helper T-cells </li></ul></ul><ul><li>Epidemiology </li></ul><ul><ul><li>Found in body fluids: blood, semen, vaginal secretions, and breast milk </li></ul></ul><ul><ul><li>Early 1980’s found in homosexual men and IV drug users, now United Nations estimates that 90% of all HIV infections are transmitted heterosexually. Was in blood, but now blood screened more completely. </li></ul></ul>24-
    45. 45. HIV and AIDS <ul><li>Prevention </li></ul><ul><ul><li>Abstinence or protection (latex condoms). </li></ul></ul><ul><ul><li>Testing in monogamous couples before having sex </li></ul></ul><ul><ul><li>Don’t share needles </li></ul></ul><ul><ul><li>Wear gloves if a health care worker </li></ul></ul><ul><ul><li>Pregnant women with AIDS: special pre-natal care and breast feeding discouraged </li></ul></ul><ul><ul><li>Use bleach, hydrogen peroxide, or heat to kill virus for medical equipment or personal care items. </li></ul></ul><ul><ul><li>Standard washing for clothing, bedding, towels </li></ul></ul>24-
    46. 46. HIV and AIDS <ul><li>How HIV causes damage </li></ul><ul><ul><li>HIV virus is an RNA virus (retrovirus) with a protein coat </li></ul></ul><ul><ul><li>Small part of virus binds to CD4 coreceptor on a helper T-cell and enters cell shedding its coat. RNA converted to DNA, using reverse transcriptase enzyme, and becomes part of helper T-cells DNA. Helper T-cell becomes an “HIV factory.” </li></ul></ul><ul><ul><li>Helper T-cells are the managers of the immune system , so their decrease leads to crippling of the immune system and certain kinds of cancer and opportunistic infections. An opportunistic infection is one that a normal immune system can fight off, but a compromised immune system can not. </li></ul></ul>24-
    47. 47. HIV and AIDS <ul><li>Early symptoms </li></ul><ul><ul><li>Flu-like symptoms, may also be night sweats, some have no symptoms </li></ul></ul><ul><ul><li>Symptoms usually disappear after a few weeks </li></ul></ul><ul><ul><li>T-cells replaced that were lost initially, but eventually replacement can’t keep up with loss leading the way for AIDS </li></ul></ul><ul><li>HIV blood tests </li></ul><ul><ul><li>Detect the presence of HIV antibodies. Show up in one month up to 6 months after infection. Therefore, even though there is a negative test, the person is still infectious if infected. </li></ul></ul>24-
    48. 48. HIV and AIDS <ul><li>When does HIV become AIDS </li></ul><ul><ul><li>When the helper T-cell count drops to below 200 cells/mm 3 </li></ul></ul><ul><ul><ul><li>Normal helper T-cell count is about 1000-1200 cells/mm 3 </li></ul></ul></ul><ul><ul><li>When an opportunistic infection or related illness develops (such as pneumocystic pneumonia or histoplasmosis) </li></ul></ul><ul><ul><li>When a particular type of malignancy develops (such as Kaposi’s sarcoma or non-Hodgkin lymphoma) </li></ul></ul><ul><ul><li>80% of AIDS-related deaths from opportunistic infections and malignancies </li></ul></ul><ul><ul><li>Also many patients have some form of CNS complications, including meningitis, encephalitis, neurologic deficits, and neuropathies </li></ul></ul>24-
    49. 49. HIV and AIDS <ul><li>Treatment options </li></ul><ul><ul><li>Current treatments alleviate symptoms or help prevent spread in the body. Many drugs - unpleasant side effects. </li></ul></ul><ul><ul><li>First drug was AZT which targets the reverse transcriptase. The HIV virus often develops a resistance to it. </li></ul></ul><ul><ul><li>New HIV drugs target other cellular activities of HIV, helping prevent HIV from replicating in the helper T-cells. Protease inhibitors. Protease cuts proteins for viral coat. </li></ul></ul><ul><ul><li>New drug: an integrase inhibitor. </li></ul></ul><ul><ul><li>“ Drug cocktails” combine 3 drugs that reduce the viral load and increase the helper T-cell count. Drugs must be taken for life. Expensive and not readily available in developing countries. Now, Atripla is a single daily dose of the 3 drugs. </li></ul></ul><ul><ul><ul><li>AZT and ddC are anti-retroviral drugs plus a protease inhibitor. </li></ul></ul></ul><ul><ul><li>Vaccine - progress has been slow. Viruses mutate rapidly. </li></ul></ul>24-
    50. 50. Autoimmune Diseases <ul><li>Body mistakenly attacks itself. </li></ul><ul><li>Examples </li></ul><ul><ul><li>Graves’ disease </li></ul></ul><ul><ul><li>Type 1 diabetes </li></ul></ul><ul><ul><li>Multiple sclerosis </li></ul></ul><ul><ul><li>Myasthenia gravis </li></ul></ul><ul><ul><li>Rheumatoid arthritis </li></ul></ul><ul><ul><li>Systemic lupus erythematosus </li></ul></ul><ul><ul><li>Guillain-Barre syndrome </li></ul></ul>24-