lymphatic-immune - Lymphatic and Immune System Cells,...

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Lymphatic and Immune System Cells, tissues and organs responsible for defending the body against pathogens, toxins, and cancer cells. Lymph: a fluid connective tissue – ground substance is lymph fluid, cells are lymphocytes – respond to - presence of pathogens (viruses/bacteria) - abnormal body cells (infected or cancerous) - foreign proteins (bacterial toxins) Cells and tissues involved with defense known as the immune system. Immune response – the responses and actions taken by the body to defend against pathogens. Lymphatic system: - lymph - lymphatic vessels - lymphoid tissues/organs - lymphocytes Primary function of the system is production, maintenance and distribution of lymphocytes. Lymphocytes primarily reside in lymphoid tissue – tonsils, spleen, thymus. They circulate in blood, but can leave capillaries to enter tissues, and lymphatic vessels. Lymphatic capillaries - Originate as blind pockets, and are larger than blood capillaries. Act as a one way valve allowing fluid to drain from the tissues into the lymphatic circulation, removing excess. This also allows larger things, such as cells, bacteria, viruses, proteins, etc. to enter the lymphatics so the lymphocytes can monitor the fluid and respond to problems as necessary. Lymphoid tissues: connective tissues with many lymphocytes. Either a nodule (no capsule, tonsil/appendix) or node. Tonsils: large nodules in walls of pharynx. Most people have 5 of them (2 palatine, one pharyngeal <aka adenoids>, 2 lingual). Can become infected, requiring removal (if infection is more than can be handled). Peyer’s patches – lymph nodules in ileum; appendix – lymph nodule in large intestine. Lymph nodes: have connective tissue capsule. Lymph flows through a network of sinuses bringing to lymphocytes inside; this way the lymph is exposed to immune cells within the lymph node. (cleaning, and checking for infection) Node is also like a filter, to purify lymph before it goes back into the venous circulation. About 99% of antigens in the lymph are removed before it leaves the node (macrophages clean up). So, lymph node is the first warning area that detects the invasion of pathogens. Swollen lymph glands often occur when activated - thisis due to increasing numbers of lymphocytes. However over-swelling can be symptomatic of things like cancers, chronic viral infections, or endocrine disorders. Draining lymph nodes – the first nodes occurring relative to an area – usually checked in cancer patients for signs of metastasis.
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Thymus: located just posterior to sternum. Younger animals have a large thymus, extending from base of neck to top border of heart. Largest in 1-2 nd year of life, relative to body size. Thereafter continues to grow up until puberty but after that point begins to involute, getting smaller and reaching smallest size around age 50. Thymus is the organ where T cells finish their maturation and undergo selection (more later on this) Spleen: contains the largest amount of lymphoid tissue in the body. Functions:
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This note was uploaded on 04/17/2008 for the course BIO 121 taught by Professor Short during the Fall '07 term at Finger Lakes Community College.

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lymphatic-immune - Lymphatic and Immune System Cells,...

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