Lecture 27Outline of Last Lecture I. The Immune SystemOutline of Current LectureI. The Immune System (Part 2)Current Lecture1. Immune System (Part 2).a. Know the main pats of the thymus: its lobes, lobules, cortex, and medulla.i. Located just anterior to the heartii. Thymus produces T cellsiii. 2 lobes: Right and Left (think of a cauliflower)1. Each have many lubules (floret of the cauliflower)2. Each has a darkly stained outer cortexa. where positive selection takes placei. the survival of those T-cell families that can recognize our own cellsii. those that cannot recognize our cells are deleted (those that do not destroy bad cells)3. Interior to cortex – lighter stained medullaa. Where negative selection takes placei. The destruction of those T-cell families that bind too strongly to self proteins (it would attack healthy cells)ii. Minimizes the chance of autoimmune diseases b. Lymphoid tissue: describe its main functions, and describe its histological structure that lets it hold many lymphocytes.i. Modified type of loose connective tissueii. Found where infections occur most ofteniii. Filled with many lymphocytes, which migrate to fight the infectioniv. Most destruction occurs herev. Most lymphocytes get activated here vi. Most effector and memory lymphocytes are produced herevii. Reticular connective tissue that form a complex network also forming a series of caves along the way, along the network are fibroblasts and macrophages1. Within these caves are many lymphocytes which have migrated from the capillaries into this often-infected tissue2. Macrophages eat and destroy many infectious microorganismsc. What are dendritic cells? What are GALT, BALT and MALT: lymphoid tissue mixed in areas with areas of areolar connective tissuei. Dendritic cells: have many long branching processes that are related to macrophages1. “professional antigen gatherers”2. Taking up antigens more avidly and in more ways than ordinary macrophagesBIOL_315 1nd Edition3. Not only lymphocytes but throughout the body4. Make our immune system more efficientii. GALT (gut-associated lymphoid tissue)- in the digestive tubeiii. BALT (bronchus-associated lymphoid tissue)- walls of the respiratory tubesiv. MALT (mucosa-associated lymphoid tissue)- GALT + BALT in urinary & reproductive tubesd. What are lymphoid nodules (follicles) and germinal centers?i. Lymphoid nodules: formed by and activated B lymphocyteii. Germinal centers: center of the lymphoid nodulee. In a lymph node, what is the functional difference between the lymph sinuses and the lymphoid tissue between these sinuses? i. Some antigens are destroyed by macrophages in the lymph sinuses, others in the lymphoid tissue between the sinuses.f. Spleen: What are the two main functions of the spleen, and how do they relate to the white pulp and red pulp?i. Functions1. Destroying blood-borne antigens and microorganisms2. Remove and destroy worn-out blood cells ii. Red pulp and white pulp perform the immune function (white) and blood-destroying function (red)g. Are splenic cords and sinusoids the main parts of the red pulp or of the white pulp? i. Red Pulph. Are lymphoid tissue and central arteries the main parts of the red pulp or the white pulp? i. White Pulpi. How does white pulp remove antigens from the blood? i. All of the cuffs of lymphoid tissue around all the central arteries= white pulpii. The central artery sends arterioles and sinusoidal capillaries into surrounding cuffof white pulpiii. Antigens from the blood leak out of these capillaries into the lymphoid tissue, where they are destroyedj. How does red pulp destroy worn-out blood cells?i. Sinusoids + splenic cords = red pulpii. Whole blood leaks out of the sinusoids into the splenic chord tissue1. Macrophages eat up those blood cells that are worn or defective 2. All unhealthy blood cells are phagocytized by these macrophages iii. Healthy blood cells leave splenic cords and return to the blood sinusoids k. When would a patient require a splenectomy? i. if the spleen were to be damaged by being punched and it ruptures or if badly infected during blood