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UNCW BIO 241 - Defense Mechanisms

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BIO 241 1st Edition Lecture 12Outline of Last Lecture I. Essential functionsII. Formation and flow of lymphIII. Lymphatic trunksIV. Lymphatic ductsV. Lymphoid tissueVI. Lymph nodesVII. Lymph node distributionOutline of Current Lecture II. TonsilsIII. SpleenIV. Thymus glandV. Resistance to diseaseVI. Lymphocytes and immunocompetenceVII. Cell-mediated immunityVIII. Antibody mediated immunityCurrent LectureII. Tonsils are located on the left and right side of the uvula. They are full full of macrophages and lymphocytes. There is also a pharyngeal tonsil known as the adenoid. Its parenchyma is made of the two WBCs mentioned above (monocytes turn to macrophages). The palatine tonsils are known to have crypts (hiding spaces) where food is known to lodge, ossify, and eventually come out orally. They function to aid lymph node distribution.III. The spleen is located deep to the lower left rib. Its parenchyma consists of white pulp (mainly lymphocytes) and red pulp (mainly RBCs). Its function is to monitor blood for antigens, for phagocytosis of old RBCs, and for blood storage. IV. The thymus gland is located under the sternum. Its parenchyma is mostly T cells. It functions in the development of T lymphocytes and it secretes signaling molecules until adulthood. After adulthood, it begins to involute and becomes fat tissue. V. A pathogen is a bacterium, virus, or other microorganism that can cause disease. There are three lines of defense to prevent a pathogen from causing disease. The first line of defense are the external barriers such as the skin and hair. The second line of defense are several non-specific defense mechanisms. The third is immunity which is specific to resistance to disease. What distinguishes nonspecific resistance (second line) from immunity are specificity and memory. Specificity is that each T cell is specific to one antigen. An antigen is anything that provokes an immune response. Most cells can discern between self cells (endogenous) and nonself cells (exogenous). VI. T cells are activated in the thymus gland and are responsible for cell-mediated immunity. B cells are made in the red bone marrow and are responsible for antibody-mediated immunity (humoral). VII. Cell-mediated immunity is directed against intracellular pathogens (viruses), some cancer cells, and tissue transplants. There are three phases that can be remembered as RAM. The R isfor recognition in which antigen presentation occurs followed by T cell activation. T cell activation multiplies so rapidly because of costimulation (cells activating cause more cells to activate) and clonal selection (the mutation of stem cells to be either helper, killer, or memory). The A is for attack in which helper T cells and cytotoxic T cells go to work. The M is for memory in which memory T cells are activated to create an anamnestic response (memory). VIII. Antibody-mediated immunity is directed against extracellular antigens. It also has the RAM phases. Recognition occurs when an antigen binds to B cell receptors followed by B cell activation and then clonal selection (stem cells turn into plasma cells that produce antibodies and memory B cells). Attack is when plasma cells secrete their antibodies. Antibodies mark antigens for destruction. Memory B cells are responsible for the anamnestic response. Luckily, Band T cells usually work


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UNCW BIO 241 - Defense Mechanisms

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