Lymphatic System & Immune System PDF

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Summaries of each section and subsection with Chapter 14 Lymphatic and Immune Systems...

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Lymphatic & Immunity

Chapter 14! Structure and Function of the Body; 15th E.

Lymphatic System Organizations of the Lymphatic System Many additional substances that cannot enter or return through the capillary walls, including excess fluids and protein molecules, are returned to the blood as lymph. Lymph is the excess fluids left behind by capillary exchange that drains from tissue spaces and is transported by lymphatic vessels.! The lymphatic system includes lymph nodes and lymphatic organs such as the thymus and spleen. Lymphatic organs helps to filter, removing harmful particles before they can cause significant damage to other parts of the body.! —————————!

Lymph Lymph formations comes about when blood plasma filters out the capillaries into the microscopic spaces between tissue cells. This is caused by the hydrostatic pressure generated by the pumping action of the heart. There, interstitial fluid (IF) is created.! The remainder of this fluid is called lymph after the IF goes back into the blood. The lymph then enters a network of tiny blind-ended tubes disturbed in the tissue spaces called lymphatic capillaries. These capillaries permit excess tissues fluid along with some other substances such as dissolved protein molecules to leave the tissue spaces.! —————————!

Lymphatic Vessels Lymphatic vessels are microscopic and are formed from sheets that consist of a single cell layer of simple squamous epithelium call endothelium. These cells are more porous and allow larger molecules including proteins and other substance, as well as the fluid itself to enter the vessel and eventually return to the general circulation. ! The movement of lymph these vessels are usually in one direction only. Lymphatic vessels often have a “beaded” appearance, resulting from the presence of valves that assist in maintaining a one-way flow of lymph. Lymph flowing in these capillaries eventually move into larger vessels known as lymphatic veins and lymphatic venules. Lymphatic vessels eventually empty into one of the two terminal vessels, right lymphatic duct and thoracic duct which returns their lumps into the blood in large veins in the neck region. Lymph from the body empties into the thoracic duct is the largest lymphatic vessel in the body while the right upper extremity and right side of head, neck and upper torso flows into the right duct. ! The thoracic duct in the abdomen has en enlarged pouch-like structured called the cisterns chyli, which serves as a temporary holding area for lymph moving towards its point of entry in the veins. Lymphatic capillaries in the walls of the small intestines are called lacteals which transport fat obtained from food nutrients into the bloodstream.! —————————!

Lymph Nodes Location and Structure Lymph nodes are located in clusters along the pathway of lymphatic vessels. Some of these nodes maybe be as small as a pinhead while other maybe as large as a lima bean. The

Lymphatic & Immunity

Chapter 14! Structure and Function of the Body; 15th E.

structures of the lymph nodes makes it possible for them perform two important immune functions: defense and white blood cell formation.! Lymph nodes are lymphatic organs because they contain lymphatic tissue, which is a white mass of developing lymphocytes and related cells. Lymphoid organs such a lymph nodes, tonsils, thyme and spleen are important structural components of the immune system because they provide immune defense and development of immune cells.!

Biological Filtration Lymph nodes perform biological filtration, a princess in which cells alter the content of the filtered fluid. Biological filtration of bacteria and other abnormal cells by phagocytosis prevents local infections from spreading. ! Lymph nodes enter the nodes through one or more afferent lymphatic vessels which deliver lymph to the node. Once a lymph enters the node, it filters slowly through spaces called sinuses that surround nodules found in the outer- cortex- and inner -medullary- area of the nodes. Lymph exits the nodes through the a single efferent lymphatic vessel.! Lymph nodes filters the lymph in a two-step process. First debris is trapped in reticular fiber that suspend the lymph nodules. Then, immune cells destroy and break apart the debris by phagocytosis and other biological processes! —————————!

Thymus The thymus is a small lymphoid tissue organ located in the mediastinum, extending upwards in the midline of the neck. The thymus plays a role a central and critical role in the body’s vital immunity mechanism. It is source of lymphocytes before birth and is then especially important in the “maturation” or development, of a type of lymphocyte that then leaves the thymus and circulates to the spleen, tonsil, lymphs nodes and other lymphoid tissues.! T lymphocytes, or T cells, are critical to the functioning of the immune system. A group of hormones secreted by thymus called thymosins influences the developments of T cells.! —————————!

Tonsils Masses of lymphoid tissues called tonsils are located in a protective ring under he mucous membrane in the mouth and back of the throat. They help protect against bacteria that may invade tissues in the area around the openings between the nasal and oral cavities.! Palatine tonsils are located on each side of the throat.! Pharyngeal tonsils, known as adenoids when they become swollen, are near the posterior opening of the nasal cavity. ! Lingual tonsils are near the base of the tongue.! ——————————!

Spleen The spleen is the largest lymphoid organ in the body as it serves as a reservoir for blood that can be returned to the cardiovascular system when needed. If damaged and bleeding, a surgical removal called splenectomy may be required to stop the loss of blood and ensure survival.!

Lymphatic & Immunity

Chapter 14! Structure and Function of the Body; 15th E.

As blood flows through the white pulp (lymphocytes), the spleen removes, by mechanical and biological filtration, many bacteria and other debris. The spleen also destroys worn out red blood cells (RBC’s), which often fall apart when passing through the spleen’s meshwork, and stages the iron found in hemoglobin for future use. ! The white pulp of the spleen also serves as a reservoir for monocytes, which can quickly lead the spleen to help repair damaged tissue anywhere in the body during an emergency.! ———————————-———————————-!

Immune System Function of the Immune System The body’s defense mechanisms protect us from disease-causing microorganisms that invade our bodies. The immune system makes us immune (able to resist these threats to our health and survival). ! Many organisms that help provide defense: lymph nodes, tonsils, thymus and spleen! —————————!

Nonspecific Immunity Nonspecific immunity is maintained by mechanisms that attack any irritant or abnormal substance that threatens the internal environment. We are born with nonspecific defenses that do not require prior exposure to a harmful substance or threatening cell, helping us note nonspecific immunity as also innate immunity and are more rapid than specific immune responses.! The inflammatory response is a set of nonspecific responses that often occurs in the body. Such signal molecules sent by cells are often called ctyokines which attracts white blood cells to the area. Many of these factors produce characteristics signs of inflammation: heat, redness, pain, swelling and sometimes fever, a state of abnormally high body temperature.!

Feedback Loop of Inflammation Response Negative: Healthy tissue -> Bacteria enters tissue -> Tissue damage occurs -> Inflammation mediators are released -> Chemotaxis, increased blood flow & vascular permeability -> increased numbers of leukocytes & mediators at site of tissue damage -> Bacteria are contain, destroyed & phagocytized -> No bacteria -> tissue repair -> healthy tissue -> … ! Positive: Healthy tissue -> Bacteria enters tissue -> Tissue damage occurs -> Inflammation mediators are released -> Chemotaxis, increased blood flow & vascular permeability -> increased numbers of leukocytes & mediators at site of tissue damage -> Bacteria are contain, destroyed & phagocytized -> Bacteria remain -> additional mediators activated -> inflammation mediators are released -> … ! ——————————!

Specific Immunity Specific immunity includes protect mechanisms that confer very specific protection against certain types of threatening microorganisms or other toxic materials. Long-term protective function called immune memory allows the immune system to effectively stop a second attack by the same specific pathogen. As it’a able to adapt to new encountered foreign materials, specific immunity is often also called adaptive immunity. Artificial exposure is called immunization and is the deliberate exposure of the body to a potentially harmful agent.!

Lymphatic & Immunity

Chapter 14! Structure and Function of the Body; 15th E.

Natural and artificial immunity can be either ‘active’ or ‘passive’.! • Active immunity occurs when an individual’s own immune system responds to an! # agent the produces an immune response, regardless of whether that agent was! # naturally or artificially produced; last longer! • Passive immunity results when immunity to a disease that has developed in another# # individual or animal is transferred to an individual who was not previously immune;! # temporary, immediate protection! ———————————-———————————!

Immune System Molecules Cytokines Cytokines are chemicals released from the cells to act as direct agents of innate, nonspecific immunity. Many od the cytokines are proteins called interleukins (ILs). ILs are often involved in signaled both the innate and adaptive immune mechanisms. !

Antibodies Defintion Antibodies are a class of proteins that are normally present in the body. A defining characteristics of an antibody molecule is the uniquely shaped concave regions called combining sites. They also have the ability to combine with a specific compound called an antigen.!

Functions Antibodies produce humoral immunity, or antibody-mediated immunity, by changing the antigens in a way that prevents them from harming the body. Once bonded with an antigen, this forms an antigen-antibody complex and if the antigen bonded with are molecules in the surface membrane of the threatening cells, they may agglutinate the enemy cells, which makes them stick together in clumps. ! One of the most important way these antibodies act is in a process called complement cascade. When antigens that are molecules on an antigenic or foreign cells surface combine with antibody molecules, they change the shape of the antibody molecule slightly but just enough to expose two previously hidden regions called complement-binding sites.! The exposure of the complement-binding sites of an antibody that is attached to an antigen on the surface of a threatening cell then permits complement proteins to initiate a series of events to kill the cell.! ——————————!

Complement Proteins Complement is the name used to describe a group of protein enzymes normally present in an inactive state in the blood. Complement cascade is a process that is a rapid-fire cascade or sequence of events that expose complement-binding sites on antibodies. ! Complement proteins also serve other roles in the immune system such as attracting immune cells to a site infection, activating immune cells, marking foreign cells for destruction, and increasing permeability of blood vessels.! ———————————-———————————!

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Lymphatic & Immunity

Chapter 14! Structure and Function of the Body; 15th E.

Immune System Cells Phagocytes Phagocytic white blood cells are an important part of the immune system and are bone marrow-derived cells that carry on phagocytosis, or ingestion and digestion of foreign cells or particles. ! Two phagocytes are neutrophils and monocytes. They migrate out of the blood and into the tissues in response to the infection. Neutrophils are functional but short lived (pus is mostly dead neutrophils). Once into the tissues, monocytes develop into phagocytic cells called macrophages. Another type of phagocytic cell is called dendritic cells (DC) in which are highly branded cells produced in bone marrow and are released into the bloodstream. ! Macrophages and DCs also act as antigen-presenting cells (APCs) as they ingest a cell or particle, remove its antigen and display of them on their cell surfaces which can be presented to other immune cells to trigger additional, specific immune responses.! ——————————!

Lymphocytes Lymphocytes are responsible for antibody production and other adaptive immune system mechanisms. They circulate the body’s fluids, searching for any enemy cells, threatening virusinfected cells and cancer cells.!

B Cells Development The first stage of B-cell development is the transformation of stem cells into immature B-cells. This occurs in the live and bone marrow before birth but only in the bone marrow in adults. Immature B-cells are small lymphocytes that have synthesized and inserted into their cytoplasmic membranes numerous molecules of one specific kind of antibody.! The second stage changes a mature, inactive B-cell into an activated one. However, this requires the activation from a cytokine from another immune cell- a T-cell. This then clones the B-cell which in each are made up from two kinds of cells:! Plasma (effector) cells secrete huge amounts of antibody into the blood. ! Memory cells can secrete antibodies but not immediately do so. They remain in reserve in the lymph nodes until they are contracted by the same antigen that led to the formation.! Function B-cells function indirectly to produce humoral immunity, the resistance to disease organism produced by the actions of antibodies binding to specific antigens while circulating in body fluids. Plasma cells are the “antibody factories” of the body.!

T Cells Development The first stage of development is within the thymus gland. The newly formed T-cells stream out of the thymus into the blood and migrate to the lymph nodes where they then reside. Each Tcell’s membrane has protein molecules that shaped to fit one specific kind of antigen.! The second stage takes place when and if a T-cell comes into contact with its specific antigen. The antigen bings to the protein on the T-cell’s surface, changing the T-cell into an activated

Lymphatic & Immunity

Chapter 14! Structure and Function of the Body; 15th E.

one once in contact with an cytokine and cloning to start the second stage again. Also having effector and memory cells, the effector cells are actively engaged in immune responses unlike its counterpart cells.! Functions Activated T-cells produce cell-mediated immunity, resistance to disease organisms that resulted from action cells- or sensitized of T-cells. Cytotoxic T-cells are activated T-cells that kill infected cells and tumor cells directly. They release a substance that acts as a specific and lethal poisoning. ! Helper T-cells, another type of activated T-cells, produce deadly effects indirectly by mens of chemical signals, one of which attracts macrophages into the vicinity area around the enemy cells! Regulatory T-cells helps shut down an immune reaction after the antigens have been destroyed and also helps precent inappropriate immune reactions.! ———————————-———————————! ! Interferon (IF): a type of smell protein compound that plays a significant role in producing! # # innate immunity against viral infections! Allergy: Hypersensitivity of the immune system to relatively harmless environments antigens.! Anaphylactic Shock: Life threatening condition caused by allergies; characterized by ! # # # constriction of the airways, relaxation of the blood vessels and! # # # irregular heath rhythms! HIV (Human Immunodeficiency Virus): RNA undergoes reverse transcription inside infected# ! # # # # # cells to form its own DNA! AIDs (Acquired Immunodeficiency Syndrome): Progression of HIV...