What are lymphatic nodules? Multiple Choice Compact masses of lymphatic tissue Regions of bone marrow that produce lymphocytes Encapsulated lymphatic organs
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Lymphatic tissues are aggregations of lymphocytes in the connective tissues of mucous membranes and various organs. Aggregated lymphoid nodules are the most prevalent lymphatic tissue in which the cells are scattered throughout the tissue. The thymus and intestinal nodules are specific lymphocyte clusters found in the ileum of the small intestine. Lymphatic nodules are dense masses of lymphocytes and macrophages that come and go as the body requires them. They are a relatively constant feature of the lymph nodes, tonsils, and appendix.
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Lymph nodes monitor and remove debris, pathogens, and excess nutrients. They accumulate cells called lymphocytes, which are produced and stored in lymphatic nodules, lymph node organs, thymus, and spleen (which spend most of their time in lymphatic tissue). They respond to antigens, which are substances that provoke an immune response. This includes T cells, plasma cells, NK cells, and B cells. Tonsils are large lymphatic nodules in the walls of the pharynx. An infection and inflammation of the aggregated lymphatic nodules in the pharynx is called tonsillitis. The spleen contains the greatest quantity of lymphatic tissue in adults. Its functions include acting as a reservoir for blood, hematopoiesis, and destruction of old red blood cells. The spleen has two types of pulp: red pulp, which contains large aggregations of lymphocytes, and white pulp, which is abundant in T cells. The thymus gland is located above the heart. It produces cells that develop from stem cells. The thymus gland has the greatest relative size at 2 years old and diminishes after puberty. It secretes thymosin, which functions to regulate T cells (thymus-dependent cells) and help regulate the immune response. B cells, also known as bone marrow-derived cells, are involved in humoral immunity. Red bone marrow contains stem cells that will form red blood cells or white blood cells. NK cells fight and kill aberrant cells, such as virally infected and tumorigenic cells. B cells release immunoglobulins, also known as antibodies. The inflammatory response is when cells release histamines and heparin. Interferons are proteins that make a cell and its neighbors resistant to virus infection.
B. The lymphatic system: organs and tissues B1. Write P next to descriptions of primary lymphatic organs and S next to descriptions of secondary lymphatic organs and tissues. a. Origin of B cells and pre-T cells b. Sites where most immune responses occur c. Includes lymph nodes, spleen, and lymphatic nodules d. Includes red bone marrow and thymus B2. Describe the thymus gland in this exercise. a. It is located in the (neck? mediastinum?). Its position is just posterior to the bone. Its size is relatively (large? small?) in childhood, -creasing in size after age 10 to 12 years. b. Like lymph nodes, the thymus contains a medulla surrounded by a . Within the cortex are densely packed -cytes. The thymus is the site of maturation of (B? T?) cells (only in childhood? throughout life?), a process facilitated by cells and also by thymic hormones produced by cells. c. The thymic medulla consists mainly of (immature? more mature?) T cells, along with several other types of cells. Some epithelial cells are located in thymic (Hassell's) . Describe the function of these cells. B3. Complete this checkpoint on lymph node structure. a. Use terms in the box to label structures A-E on Figure LG 22.1. ALV. Afferent lymphatic vessel ELV. Efferent lymphatic vessel GC. Germinal center MS. Medullary sinus TS. Trabecular sinus b. Now write one answer from the box above on each line next to related descriptions. 1. Vessels for entrance of lymph into node: 2. Vessel for exit of lymph out of node: 3. Region composed of antigen-presenting cells, B cells that become either plasma cells or memory cells, and macrophages:
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