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Thymus, spleen, tonsils

Thymus, spleen, tonsils. Dora Malić Medical English, 2013/14 Mentor: A. Žmegač Horvat. Thymus. Anterior superior mediastinum Two asymmetrical lobes Each lobe composed of lobules Lobule – outer cortex and inner medulla. Two types of cells

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Thymus, spleen, tonsils

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  1. Thymus, spleen, tonsils Dora Malić Medical English, 2013/14 Mentor: A. Žmegač Horvat

  2. Thymus • Anterior superior mediastinum • Two asymmetrical lobes • Each lobe composed of lobules • Lobule – outer cortex and inner medulla

  3. Two types of cells • stromal cells- cortical epithelial cells, thymic medullary epithelial cells, dendritic cells - selection of functional and self-tolerant T-cell receptors • cells of hematopoietic origin – derived from bone marrow hematopoietic stem cells

  4. Function of thymus • Maturation of T-cells • Migration of hematpoietic progenitor cells from bone marrow • Thymocytes undergo: • positive selection – those with no affinity for self-MHC on stromal cells are destroyed • negative selection – those with high affinity for thymic antigens are destroyed – central tolerance

  5. Involution of thymus • largest and most active during the neonatal and pre-adolescent periods

  6. Spleen • Upper left quadrant of the abdomen • Not a vital organ • Surrounded by a fibrous capsule • Composed of red and white pulp

  7. Structure of spleen • Red pulp • sinuses – vessel-like spaces filled with blood • splenic cords– reticular fibers • marginal zone bordering on white pulp • White pulp - nodules -Malpighiancorpuscles • follicles - rich in B-lymphocytes • periarteriolarlymphoid sheath - T-lymphocytes

  8. Functions of spleen • Removes old red blood cells from circulation • Reserve of blood • Storage of red blood cells, platelets, and lymphocytes • Metabolizes hemoglobin • Recycles iron • Part of mononuclear phagocyte system • Active immune response to antigens

  9. Tonsils • Collections of lymphoid tissue in aerodigestive tract • Waldayer’s tonsillar ring - adenoid tonsil, two tubal tonsils, two palatine tonsils, lingual tonsil • First line of defense against ingested or inhaled foreign pathogens

  10. Palatine tonsil • Non-keratinized stratified squamous • Incompletely encapsulated • Long, branched crypts • Sides of oropharynx - between palatoglossaland palatopharyngeal arches • Tonsillectomy

  11. References • http://en.wikipedia.org/wiki/Tonsil • http://en.wikipedia.org/wiki/Lymph_node • http://www.webmd.com/digestive-disorders/picture-of-the-spleen • http://en.wikipedia.org/wiki/Thymus

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