LYMPHATIC AND IMMUNE SYSTEMS. Chapter 33

Transcription

1 LYMPHATIC AND IMMUNE SYSTEMS Chapter 33

2 THE LYMPHATIC SYSTEM The lymphatic system has three main functions Take up excess tissue fluid and return it to the bloodstream Receive fats called lipoproteins and return them to the blood stream Work with the immune system for defense against disease The lymphatic system is a one-way system. Lymphatic capillaries absorb fluid in the blood that has not been reabsorbed by the blood capillaries. At this point, the fluid is called lymph

3 THE LYMPHATIC SYSTEM The lymphatic capillaries join to lymphatic vessels that enter either the thoracic duct or the lymphatic duct. The thoracic duct serves the lower extremities, abdomen, and left side of the head, neck and torso The lymphatic duct serves the right side of the head, neck, and torso Both ducts remove harmful substances from blood and carry them to lymph nodes where they are isolated from the rest of the body

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6 LYMPHOID ORGANS Lymph nodes Lymph nodes are found along the lymphatic vessels. A lymph node contains a cortex and a medulla Cortex: where lymphocytes congregate when fighting off a pathogen (hence, the swelling of the lymph nodes if a patient is sick or fighting a disease) Medulla: where macrophages cleanse the lymph as it passes through Lymph nodes are found in the groin, armpits, and neck and tend to swell when isolating and containing pathogens

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9 LYMPHOID ORGANS Tonsils Tonsils are located just above the pharynx Tonsils behave like lymph nodes for pathogens and antigens that enter the body through the mouth and nose The function of tonsils was only recently discovered in the past century, making the 3,000 year old surgery of tonsillectomy much more rare

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11 LYMPHOID ORGANS Spleen The spleen is the primary blood filtering organ Located in the upper left abdominal region, just beneath the diaphragm Spleens contain two tissues called white pulp and red pulp. The white pulp filters out bacteria and debris from blood The red pulp filters out old red blood cells

12 LYMPHOID ORGANS Thymus gland Located along the trachea behind the sternum T lymphocytes mature in the thymus Immunity hormones, such as thymosin, are produced here Bone Marrow Contains the stem cells for all types of blood cells The bone marrow is connected to sinuses, where matured and differentiated blood cells enter the blood stream

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16 IMMUNE SYSTEM: INNATE DEFENSE Immunity is the body s ability to defend itself against infectious agents, foreign cells, and even abnormal body cells such as cancer. Innate defense systems recognize most common microbe invaders automatically whether or not the immune system has encountered this particular microbe before. They lack any memory system. Even if they encounter the same microbe 1000 s of times the response doesn t change.

17 INNATE IMMUNITY: P HYSICAL & CHEMICAL BARRIERS Skin and mucus membranes limit where pathogens can enter the body to only a few locations (mouth, nose, ears, genitals) Oil secretions contain additional chemicals that weaken or kill some bacteria that make contact with the skin Respiratory tracts are lined with cilia. Mucus surrounds and collects pathogens, then cilia sweep the pathogen to the throat where it can be swallowed or expectorated (coughed out) Symbiotic bacteria in our bodies also fight off invaders

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20 INNATE IMMUNITY: INFLAMMATORY RESPONSE Damaged tissues initiate an inflammatory response which makes both the organism and the immune system aware of a problem. Inflamed areas show redness, heat, swelling and pain. Histamines trigger the capillaries of the tissues to dilate and allow a higher volume of blood cells to enter. White blood cells enter the area to cleanse any foreign microbes Clotting occurs to prevent any bacteria from entering while the tissue is repaired and allow the internal homeostatic environment to continue.

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22 PHAGOCYTES AND NKC S Natural Killer Cells NK cells kill virus-infected cells and tumor cells. They are triggered only by chance cell-to-cell encounters They know if a cell is foreign because the cell doesn t know how to build the specific antigens for that cell Neutrophils These immune cells can leave bloodstreams and enter tissues to fight infections Eosinophils These cells are designed to attack larger parasitic infections like roundworm or tapeworm that are too big for individual phagocytizing cells.

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24 INNATE IMMUNITY: PROTECTIVE PROTEINS Protective Proteins are produced in a domino effect called the complement system. One protein activation triggers production of all others These proteins are only activated by pathogens and work in one of three ways: 1: They increase the inflammation response if large microbes are involved 2: They increase phagocytosis by binding to pathogens and giving neutrophils and macrophages something to latch on to. 3: They poke holes in pathogens to force water and salts to enter until the molecule bursts. Interferon is a protective protein produced by virus-infected cells. Interferon binds to non-infected cells causing them to go into hibernation mode and limiting the number of cells the virus could spread to.

25 IMMUNE SYSTEM: ADAPTIVE DEFENSE Adaptive defenses are designed to respond to specific diseases with higher frequency after each encounter Adaptive defense relies on B cells (which are made in marrow) and T cells (which are made in the thymus) Both B and T cells recognize your personal antigens and distinguish them from other microbial antigens B and T cells have millions of different antigen receptors on their plasma membranes for recognizing foreign invaders. The simplest difference between B cells and T cells is that B cells attack pathogens from the outside and T cells attack from the inside.

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27 B CELLS & ANTIBODY-MEDIATED (HUMORAL) IMMUNITY Antibodies help to prevent an infection BEFORE it occurs Antibodies match with antigens and act as beacons for the immune system to respond to. They also cover the invading microbes to the point that it has difficulty binding to a new victim cell Microbes are delivered to the spleen and lymph nodes thanks to the lymphatic system, where B cells are waiting for them.

28 B CELLS & ANTIBODY-MEDIATED (HUMORAL) IMMUNITY When the B cell finds the antigen on a microbe it divides over and over again creating Plasma Cells: Cells filled with Rough ER for producing antibodies that match with this specific antigen Memory B Cells: Seek out this specific antigen for increased immune response. The most common antibody is IgG, a Y-shaped protein. The Y-shape is altered in the presence of specific antigens Leukocytes recognize the shape of this antigen and begin phagocytosis.

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30 T CELLS & CELL-MEDIATED IMMUNITY T cells come in two categories: helper and cytotoxic. Helper T cells cannot recognize foreign antigens on their own. Antigen presenting cells seek out and respond to foreign antigens. When they find an antigen, they cap it with an MHC protein. The MHC protein then attracts a helper T cell which binds to the microbe. Helper T cells attract B cells to the microbe Helper T cells also clone themselves upon binding to a microbe to create memory T cells, which look for the same microbe in the future to attract T cells. At this point, B cells would normally have completed their task. But T cells go one step further.

31 T CELLS & CELL-MEDIATED IMMUNITY Cytotoxic T cells contain vacuoles filled with a chemical called perforins and granzymes The cytotoxic T cell is incredibly deadly, so it can only be activated with the presence of specific MHC proteins and helper T cells When the cell locates its target, perforins create a pore in the plasma membrane of the microbe or cancerous cell Granzymes then enter the cell through the pore and force apoptosis

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33 ACTIVE INDUCED IMMUNITY Active immunity is your body s direct response to a specific threat. We can artificially preempt an active immune response thanks to immunizations A vaccine is a substance that contains the antigen to which the immune system responds (not the whole cell, just the antigen) and produces antibodies Antibodies are destroyed every time they fight off an infection. Unless your body makes new antibodies, you ll eventually run out. Over the course of the year or lifetime the titer will eventually dwindle as the antibodies are used up or broken down while fighting off disease Some vaccines are good for life; other s require periodic booster shot

34 PASSIVE INDUCED IMMUNITY Passive immunity is when an individual is given prepared antibodies through natural means to combat a disease. Infants are given antibodies from their mother through blood that passes the placenta or through transfer within breast milk

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36 IMMUNITY DISORDERS Allergies are hypersensitivities to substances that ordinarily would do no harm to the body. The response to these antigens, called allergens, is either: Immediate Allergic Response An IAR can occur within seconds. Coldlike symptoms are common, but the worst-case scenario is anaphylactic shock, a sudden drop in blood pressure. IgE Antibodies attached to the plasma membrane of tissue and blood release histamines as if a dangerous pathogen just invaded them, triggering these cold or anaphylactic symptoms Delayed Allergic Response Memory T cells are initiated at the site of the allergen. These trigger cytokines, which trigger the immune response.

37 IMMUNITY DISORDERS Autoimmune disease is when cytotoxic T cells or antibodies accidentally attack the body s own cells. These are sometimes the result of overactive T cells still functioning after a foreign-pathogen-initiated infection has occurred. Lupus, rheumatoid arthritis, and muscular disorders are believed to be triggered by an autoimmune disease.