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Lymphatic and Immune Systems Notes

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Lymphatic and Immune Systems Notes Lymphatic and Immune Systems Notes The lymphatic system in general: The lymphatic system is a vast collection of cells and biochemical that travel in lymphatic vessels, and the organs and glands that produce them o It is closely associated with the cardiovascular system because they both circulate fluid throughout the body and lymph (fluid) in formed from plasma o Protects against infections from pathogens (bacteria, viruses, parasites, etc.) o Lymphatic pathways begin at lymphatic capillaries which interweave between cardiovascular capillaries . Lymph node (bulb) > Lymphatic trunks (like arteries or veins) > Lymphatic capillaries (like cardiovascular capillaries) o Walls of the lymphatic vessels are thin and open up with one-way valves at the capillaries to take in lymph . These all lead to lymph nodes which collect fluid, filter it, and release it back to the body (up to 3 liters a day! That’s more than half your body fluids) The right thoracic duct rotates from right thoracic area to right jugular to right subclavian, and right upper limb Thoracic duct rotates lymph for the rest of the body o Lymph fluid is mostly plasma but without some of the nutrients so that it can enter the valves of lymphatic capillaries o Fluid is moved from high to low pressure (osmosis) as well as pushed along by contracting muscles . This prevents fluid from accumulating which causes edema a.k.a. swelling . Function of lymph: 1. Absorb dietary fats from intestines 2. Return small proteins to body and blood 3. Transport foreign particles to lymph nodes for destruction Lymphatic and immune system specifics: Lymph nodes are glands with specialized cells called lymphocytes and macrophages which are used to destroy foreign particles o Lymph nodes make lymphocytes (check thymus and spleen for the “how”) 1. B cells: immune cells produced in bone marrow 2. T cells: thymus derived cells; immune cells produced by thymus 3. NK cells: natural killer cells are different from B and T cells because they produce the cytotoxins to kill cancer cells Lymph nodes can also control lymph nodules which function singularly from the lymph flow 1. Tonsils: these glands are located at the top of the esophagus; filter anything that comes in through the mouth (breathing, eating, etc.) 2. Peyer’s Patches: these are the mucosal linings of the small intestines; covered in microvilli (similar to cilia or microscopic hairs); help remove foreign particles 3. MALTs: (mucosal-something-lined-something) a general term for any mucus lined structure: tonsils, Peyer’s patches, appendix, and spleen Lymph nodes are found in groups or chains along paths of vessels throughout the body o The major areas you should be aware of are listed below but be careful of the name and its actual description . Cervical region: under the jaw (you can feel these with your fingers) . Axillary region: armpits . Inguinal and Pelvic regions: genital and pelvic areas Lymph and lymphocytes are produced in 2 key areas o Thymus: near base of heart (remember that’s the “top”); just above the aortic arch (looks like it sits on top of the arch) . T cells are produced here; most other lymphocytes are produced in bone marrow . T cells remain inactive as part of acquired immunity These are called on for specific pathogens; fight infections o Spleen: above the kidneys but below the diaphragm, lateral to stomach . Looks like a giant lymph node but filled with blood not lymph White pulp: look like tiny islands and packed with lymphocytes Red pulp: fills space between islands; mostly red blood cells and some lymphocytes . Main purpose is to removed cell debris and dead/old cells which ends up mixed in with the red blood cells Natural immunity vs acquired immunity Natural immunity – general; used to protect against a variety of pathogens; “every day” protection; cuts, scrapes, splinters, etc. o Uses “first-line” defenses; rapid 1. Skin or mucous linings 2. Phagocytes just below skin’s surface can engulf pathogens 3. Phagocytosis is “cell-eating” or when a cell engulfs other particles 4. Use proteins to further destruction Natural Defenses What is it? 1. Species Resistance 2. Mechanical Barriers 3. Chemical Barriers 4. NK Cells 5. Inflammation 6. Phagocytosis 7. Fever Acquired immunity – carried out by specialized lymphocytes o Happens slowly/overtime o Antigens (cells recognized as non-self) o Humoral immunity against antigens (fluid mediated) . Uses B cells, B memory cells, plasma cells, and antibodies . Most commonly fights bacterial infections o Cellular immunity (infected cells) . T cells, T memory cells, helper cells, and cytotoxic cells . Most commonly fights viral infections Acquired Defenses What is it? 1. Antigens/Antigen-presenting cells 2. T cells 3. B cells 4. Cytotoxic cells 5. Helper and Memory cells 6. Plasma Cells 7. Antibodies Steps in Antibody Production T Cell Activities Antigen (nonself) connects to an antigen-presenting cell (self) Antigen-presenting cell activates the T cells o Or B Cells (discussed further down) T cells interact directly with antigen and antigen-presenting cell o Interaction is called cellular immune response T cells produce cytokines (peptides that enhance cellular response) which trigger the release of B cells T helper cells tell B cells to produce antibodies for specific antigens o Cytotoxic cells (specialized T cells) target cancerous cells and virally infected cells o Cytotoxic cells give rise to T memory cells to further immunity B Cell Activities Antigen connects to antigen-presenting cell Antigen-presenting cell activates B cells o Usually requires T cells to activate them first If T cells encounter B cells interacting with antigen, it uses T helpers to make the B cells produce antibodies o Attracts macrophages to create a “closed” or isolated inflammation area o B cells can create plasma cells which also produce antibodies o This antibody-lead immune response is called humoral immune response o Only one type of B cell produces one type of antibody Antibodies: What are they and How Do They Work? Structure: 4 chains of amino acids linked together in a Y shape o 2 identical light chains o 2 identical heavy chains (heavy because they have more amino acids) They have a variable region which is used to match to antigens o The following parts connect together . Antigen-binding sites on the antibody . Idiotypes on antigens Antibodies react to antigens in 3 ways o Direct attack: antibodies attach to antigens and cause them to clump together so phagocytes can engulf them easier o Activate Complement: complements (proteins that bind to antigens) cover antigen-antibody complexes for easier phagocytosis o Inflammation: (a.k.a. stimulate localized changes) can damage tissues but prevents infection from spreading (edema caused by vasodilation and release of histamines) Primary and Secondary Immune Responses Primary: when B and T cells are activated after first encountering antigens o Travel through blood for many weeks and eventually create memory cells o Short-lived Secondary: when memory B and T cells are sued for viral infection and after initial infection o These live a long time in blood Bacteria Virus Shapes of cells Round, pill, spiral, and comma Spherical, helical, polyhedral, and complex Infection Uses toxins: microbes can release a toxin Inject its DNA into host cell, uses that poisons your body host cell’s DNA to copy itself, bursts Destroys tissues: produces enzymes that out of host cell to spread copies “digest” your tissues Treatment Antibiotics: chemicals that inhibit growth Vaccines: weakened form of of or kills microbes in an organism pathogen injected to prepare immune system to recognize and destroy pathogen Examples 1. 1. 2. 2. 3. 3. 4. 4. 5. 5. Allergic Reactions Immune response to non-harmful substance cause by: o Hypersensitivity o Inherited tendency o Triggered by specific antigens called allergens Immediate-reaction: occurs within minutes after first contact o Release of histamines, dilate arterioles, and increase vascular permeability = edema and constriction of bronchial (lungs) and intestinal smooth muscles o Hives, asthma, eczema, gastric disturbances o Anaphylactic shock . Very sudden and overwhelming feeling . Severe swelling of tongue, mouth, larynx (windpipe), and vomiting . Cure: needs injection of epinephrine (adrenaline) and sometimes a tracheotomy (direct incision into larynx) to restore breathing and decrease swelling Usually caused by insect stings and penicillin Other allergens cause a similar reaction but usually not as severe Hypersensitivities o Takes 1-3 hours to develop antibodies o Blocks vessels which damages tissues o Leads to autoimmunity = loss of ability to tolerate self-antigens Delayed-reactions o Happens to anyone; caused by repeated exposure . Chemicals (household and industrial) and cosmetics (makeup, soap, and lotions) o Due to build up on the skin which attracts T cells (takes about 48 hours) Autoimmunity Immune system fails to distinguish self from nonself o Produces autoantibodies (antibodies that attack own cells) as well as T cells and cytotoxic cells that attack tissues and organs Beginnings of autoimmunity are not well known and are still being studied; the following are some examples 1. Viruses infect a host cell and uses its DNA to “turn into” the host cell by mimicking the appearance of the host cell 2. Immune system figures out what the fake host cells looks like and forms antibodies for it but never fully differentiates self from nonself for the rest of your life 3. Nonself antigen reassembles as self; some infections naturally reassembles our cells and are changed into self-cells 4. In some women, fetal cells remain throughout life but hide until middle age; these cells turn into a genetically distinct cell population called a mosaic; begin to form hard patches on the skin and become an autoimmune disorder as self-cells try to fight of genetically distinct cells Transplant and Tissue Rejections The donor’s cells are recognized as foreign and are attacked or destroyed by recipient’s cells o Common with any transplant (bone, corneas, kidneys, lungs, pancreases, bone marrow, skin, livers, and hearts) o Resembles cellular immune response .
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