What makes up the lymphatic system?
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The lymphatic system is made up of: lymph vessels, fluid, and nodes. The lymph nodes are especially important because they filter the fluid that moves through body tissues. The lymph is basically like giving a baby a bath. A baby is picked up, put into the tub to be cleaned, and then put back into the playroom. Lymph fluid does the same thing; it picks up particles, cleans the fluid, and puts in back into your lymphatic system (basically, the janitor of your body). Movement of lymph fluid is done by the pulsations of arteries, skeletal muscle movement, and breathing. The vessels of lymph are present everywhere except for in our bones, teeth, bone marrow, and the CNS. Lymphatic vessels, trunks, nodes and capillaries all fit together to build the lymphatic system that flows towards the heart. The order of movement of fluid through the lymphatic system is:
Lymphatic capillaries: very permeable, similar to blood capillaries, have one way valves
Lymphatic collecting vessels: similar to structure of veins, thinner, more valves.
Vessels that are toward the skin surface run along superficial veins, deep vessels run along arteries
Lymphatic trunks: created by combining collecting vessels (the system is building!)
Collecting ducts: lymph is delivered to Lymphatic (drains right upper arm and head) or Thoracic duct (drains rest of body).
Lymph nodes: these run along the lymph vessels are the cause of throat pain when you palpate near your carotid artery when you are sick. They serve as a filtration system in our body and give a chance for WBC to mount an attack by trapping debris.
Lymphatic capillaries: very permeable, similar to blood capillaries, have one way valves
Lymphatic collecting vessels: similar to structure of veins, thinner, more valves.
Vessels that are toward the skin surface run along superficial veins, deep vessels run along arteries
Lymphatic trunks: created by combining collecting vessels (the system is building!)
Collecting ducts: lymph is delivered to Lymphatic (drains right upper arm and head) or Thoracic duct (drains rest of body).
Lymph nodes: these run along the lymph vessels are the cause of throat pain when you palpate near your carotid artery when you are sick. They serve as a filtration system in our body and give a chance for WBC to mount an attack by trapping debris.
Lymphocytes: the real dirty work
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The two main fighters of our immune system are the T cells and B cells. Others include reticular cells, dendritic cells, and macrophages (these activate T cells). T cells attack and destroy foreign cells that do not belong to the body. The invaders that are caught by a T cells usually have a strange marker on their surface that our body can see as foreign. T cells are developed in the thymus and are a part of cell mediated immunity (no antibodies, rather it activates other cells--macrophages). T cells can either be under positive or negative selection pressures. Positive pressure makes sure that the T cells can recognize MHC proteins (discussed below) and negative pressure makes sure to destroy the T cells that destroy self antigens. B cells produce plasma cells, which secrete antibodies. They have membrane bound antibodies that can activate the entire cell once an antigen binds to it. Helper T-cells also help to activate the B-cell; once' activated, the cell diffrentiates and clones itself into memory (remembers antigen) or effector cells (turn into antibody factories to fight antigen, also called plasma cells). B cells are made in the bone marrow. See picture to the left for a visual of these cell types.
Lymphatic Organs & Structures
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Lymph nodes are the main part (most well-known) of the lymphatic system, probably because we notice them in our throat when we are sick. These nodes have dividing B cells in their cortex. When lymph fluid passes through a node, it is almost like a car going through a car wash. The fluid is cleaned and bacteria are wiped out by the lymphocyte WBC's. The spleen is the largest lymphatic organ that functions to clean blood of dead blood cells and other collected blood waste. Because this is a place of blood cell breakdown (when they are unhealthy), the spleen is also where leftover products of blood are stored. In a fetus, their red blood cells (erythrocytes) are created here. Compared to the lymph nodes which have lymphocytes, the spleen has both lymphocytes and monocytes. The thymus is a lymphatic organ that is most active during childhood as one's immune system is being built up--it is a "school" for WBC's to learn what to attack. It is different from other lymphatic organs in that it "functions strictly in lymphocyte maturation and does not directly fight antigens". The tonsils, those things most people get removed as a child, are the simplest of the lymphatic organs. They are only covered with a layer of epithelial tissue and want to be as exposed as possible to catch pathogens that go through your mouth. There may be holes in your tonsils called crypts. These serve to catch bacteria and fight them off there. This plan can backfire however, and sometimes a virus or bacteria will survive and sometimes even grow in the crypts. This is one reason people often have their children get tonsillectomies.
IMMUNITY -- Innate & Adaptive
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Innate: non-specific, elimnates anything that doesn't belong in our bodies, foreign particles. This has two lines of defense, external body membranes and then phagocytes along with inflammation & fever to attract more cells to site of interest. This is first/second to react.
Defenses include: skin (acidity), mucus membranes, secretions, salt in sweat, lysozyme of sweat and tears, and cells mentioned in the blue bubble in the image to the left.
Neutrophils and macrophages particpate in phagocytosis. This is when a cell destroys a pathogen with lysozome enzymes by ingesting the pathogen or oxidizing it with hydrogen peroxide (destroying it).
Natural killer cells: these cells are special because they look for cells without surface markers, i.e. cancer cells that have mutated (suppose after a long day in the sun, exposure to UV rays and mutated cells as a product). These cells induce apoptosis, or cell death, basically forcing that marker-less cell to die. NK cells also help the inflammatory response (helps to prevent spread of harmful agent and helps repair of injured tissue by triggering vasodilation for blood movement and increased permeability in capillaries).
Interferons: Interferons are a type of antimicrobial protein, they hinder a microorganisms ability to reproduce. Interferons are the "neighborhood watch" of the cell responses. When a cell is infected with a virus, they secrete IFN's (interferons) and these move to cells around it and continue down the line of tissue. The IFN's tell other cells to start making antiviral proteins. IFN's allow other cells to know what is going on around them, a neighborhood watch! They are produced by many different body cells and function to activate macrophages and allow NK cells to move around (releasing the dangerous dogs to catch the neighborhood invader).
THE PHENOMENON OF FEVER: When you get a fever, you feel sweaty and at the same time, you feel the chills. When leukocytes and macrophages come in contact with invaders, they release PYROGENS (fire-generator), these work to increase your body temperature. When you feel the chills, your "thermostat" is rising but your body tissues are still cold, they must shiver to warm up to the right temperature. When you sweat, your body is warmer than the thermostat, and your blood vessels dilate to let heat out of your tissues. Fevers are beneficial to denature proteins of invaders; a fever also keeps zinc in your spleen, sparing it from microorganisms that need it to grow. High fevers are dangerous beyond 103 degrees as our human cell proteins will denature too.
Defenses include: skin (acidity), mucus membranes, secretions, salt in sweat, lysozyme of sweat and tears, and cells mentioned in the blue bubble in the image to the left.
Neutrophils and macrophages particpate in phagocytosis. This is when a cell destroys a pathogen with lysozome enzymes by ingesting the pathogen or oxidizing it with hydrogen peroxide (destroying it).
Natural killer cells: these cells are special because they look for cells without surface markers, i.e. cancer cells that have mutated (suppose after a long day in the sun, exposure to UV rays and mutated cells as a product). These cells induce apoptosis, or cell death, basically forcing that marker-less cell to die. NK cells also help the inflammatory response (helps to prevent spread of harmful agent and helps repair of injured tissue by triggering vasodilation for blood movement and increased permeability in capillaries).
Interferons: Interferons are a type of antimicrobial protein, they hinder a microorganisms ability to reproduce. Interferons are the "neighborhood watch" of the cell responses. When a cell is infected with a virus, they secrete IFN's (interferons) and these move to cells around it and continue down the line of tissue. The IFN's tell other cells to start making antiviral proteins. IFN's allow other cells to know what is going on around them, a neighborhood watch! They are produced by many different body cells and function to activate macrophages and allow NK cells to move around (releasing the dangerous dogs to catch the neighborhood invader).
THE PHENOMENON OF FEVER: When you get a fever, you feel sweaty and at the same time, you feel the chills. When leukocytes and macrophages come in contact with invaders, they release PYROGENS (fire-generator), these work to increase your body temperature. When you feel the chills, your "thermostat" is rising but your body tissues are still cold, they must shiver to warm up to the right temperature. When you sweat, your body is warmer than the thermostat, and your blood vessels dilate to let heat out of your tissues. Fevers are beneficial to denature proteins of invaders; a fever also keeps zinc in your spleen, sparing it from microorganisms that need it to grow. High fevers are dangerous beyond 103 degrees as our human cell proteins will denature too.
THE ADAPTIVE IMMUNE SYSTEM:
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Adaptive: specific, learns to look for a specific feature. This takes longer to respond to invaders than the innate system. This immunity can be broken into HUMORAL (B-cells, creates antibodies to attract COMPLEMENTS--blood proteins that create holes in invader cells and cause them to lyse) and CELLULAR immunity (T-cells, phagocytosis, attack without using antibodies). Adaptive immunity has a "memory" of what it previously fought off. This is third to react.
T & B cells are also called lymphocytes and when they mature, they are able to recognize and bind to a specific antigen. They also show self-tolerance and do not attack our own body antigens (ideally).
MHC proteins:
When you hear this term, think "nametag". Each of our body cells has a nametag that makes it OUR cell. Class I MHC proteins are found throughout the body in all cells except RBC's. Class I MHC proteins bind to endogenous antigens, those antigens that are OURS--made in the cell--and then the cell puts them on display outside the membrane. CYTOTOXIC T CELLS check displays to make sure body cells are displaying what they should be, and if not, destroy them (includes cancer cells, foreign transplant tissues, virus-infected cells). Class I MHC's are what give our cells "nametags". Class II MHC proteins are found on certain cells of the immune system (B & T cells). These are displayed by APC's (antigen-presenting cells), dendritic cells, macrophages and B-cells. Class II MHC proteins bind to proteins that have been ingested AND that are foreign. When a cell is infected, the MHC protein will carry the foreign antigens. When a phagocytic cell ingests matierals, it becomes an APC. HELPER-T CELLS will bind to the presenting antigen on the APC and the T cell will be activated by APC surface proteins. APC's also release interleukins (Il-1 & Il-2) that cause the T-cell to differentiate, form clones, and grow. ALL MHC proteins are made in the endoplasmic reticulum of the cell.
Macrophages: present antigens and help to activate a T-cell, usually these remain in one spot in the lymphatic organs
Dendritic cells: these take in antigens and enter the lymph fluid and show the antigens they caught to the T-cells. An activated T-cell releases chemicals to stimulate macrophage activity.
TWO PARTS OF THE ADAPTIVE IMMUNE SYSTEM: HUMORAL & CELLULAR
1. HUMORAL: occurs in the fluid, when a B-cell encounters its antigen (that matches its receptor), the antigen is brought in the cell by endocytosis, the B-cell begins to make clones of itself with the same receptors. These clones turn into plasma cells, or cells that make antibodies. These antibodies move throughout the blood and lymph to attach to antigens and "mark them for destruction". However, some clone cells do not become plasma cells, they become memory cells. These cells are equipped to fight the same antigen faster the next time it prevents itself in our systems. Instead of taking a week to start combating an invader, our memory cells can attack within hours and are effective at 2-3 days!
Humoral immunity can be broken down into:
a. active: this can be either natural immunity acquired from exposure to bacterial or viral infection--OR artificial immunity acquired by cells in response to a vaccine (just antigens of pathogen)
b. passive: this too can be either natural immunity, where antibodies are delivered through a placenta--OR artificial immunity such as injection of the antibody IGg, protection ends when this antibody degrades.
2. CELLULAR: Instead of targeting bacteria, cellular immunity targets body cells that are infected, abnormal cell types, such as cancer cells. T-cells are the main cell type in this category and include Helper T-cells (CD4's), Cytotoxic cells (CD8's), Natural killer cells, and Regulatory cells.
T & B cells are also called lymphocytes and when they mature, they are able to recognize and bind to a specific antigen. They also show self-tolerance and do not attack our own body antigens (ideally).
MHC proteins:
When you hear this term, think "nametag". Each of our body cells has a nametag that makes it OUR cell. Class I MHC proteins are found throughout the body in all cells except RBC's. Class I MHC proteins bind to endogenous antigens, those antigens that are OURS--made in the cell--and then the cell puts them on display outside the membrane. CYTOTOXIC T CELLS check displays to make sure body cells are displaying what they should be, and if not, destroy them (includes cancer cells, foreign transplant tissues, virus-infected cells). Class I MHC's are what give our cells "nametags". Class II MHC proteins are found on certain cells of the immune system (B & T cells). These are displayed by APC's (antigen-presenting cells), dendritic cells, macrophages and B-cells. Class II MHC proteins bind to proteins that have been ingested AND that are foreign. When a cell is infected, the MHC protein will carry the foreign antigens. When a phagocytic cell ingests matierals, it becomes an APC. HELPER-T CELLS will bind to the presenting antigen on the APC and the T cell will be activated by APC surface proteins. APC's also release interleukins (Il-1 & Il-2) that cause the T-cell to differentiate, form clones, and grow. ALL MHC proteins are made in the endoplasmic reticulum of the cell.
Macrophages: present antigens and help to activate a T-cell, usually these remain in one spot in the lymphatic organs
Dendritic cells: these take in antigens and enter the lymph fluid and show the antigens they caught to the T-cells. An activated T-cell releases chemicals to stimulate macrophage activity.
TWO PARTS OF THE ADAPTIVE IMMUNE SYSTEM: HUMORAL & CELLULAR
1. HUMORAL: occurs in the fluid, when a B-cell encounters its antigen (that matches its receptor), the antigen is brought in the cell by endocytosis, the B-cell begins to make clones of itself with the same receptors. These clones turn into plasma cells, or cells that make antibodies. These antibodies move throughout the blood and lymph to attach to antigens and "mark them for destruction". However, some clone cells do not become plasma cells, they become memory cells. These cells are equipped to fight the same antigen faster the next time it prevents itself in our systems. Instead of taking a week to start combating an invader, our memory cells can attack within hours and are effective at 2-3 days!
Humoral immunity can be broken down into:
a. active: this can be either natural immunity acquired from exposure to bacterial or viral infection--OR artificial immunity acquired by cells in response to a vaccine (just antigens of pathogen)
b. passive: this too can be either natural immunity, where antibodies are delivered through a placenta--OR artificial immunity such as injection of the antibody IGg, protection ends when this antibody degrades.
2. CELLULAR: Instead of targeting bacteria, cellular immunity targets body cells that are infected, abnormal cell types, such as cancer cells. T-cells are the main cell type in this category and include Helper T-cells (CD4's), Cytotoxic cells (CD8's), Natural killer cells, and Regulatory cells.
ANTIBODIES
Types: IgM, IgA, IgD, IgG, IgE (Spells GAMED--memory tool)
IgM: first antibody to respond, first to react to newborn Rh+ blood coming in contact with mother's Rh- blood (no risk the first time, this antibody can NOT fit through a placenta.
IgA: present in mucus, helps to prevent the entry of more pathogens
IgD: this is a B-cell receptor (this is the ONLY antibody actually bound to a cell membrane!)
IgG: makes up MOST of the antibodies in our plasma. This CAN cross placental border and cause harm to the Rh- mother giving birth to a Rh+ baby.
IgE: works in allergies and parasitic infections, this is what causes basophils to release histamine!
IgM: first antibody to respond, first to react to newborn Rh+ blood coming in contact with mother's Rh- blood (no risk the first time, this antibody can NOT fit through a placenta.
IgA: present in mucus, helps to prevent the entry of more pathogens
IgD: this is a B-cell receptor (this is the ONLY antibody actually bound to a cell membrane!)
IgG: makes up MOST of the antibodies in our plasma. This CAN cross placental border and cause harm to the Rh- mother giving birth to a Rh+ baby.
IgE: works in allergies and parasitic infections, this is what causes basophils to release histamine!