histology exam 3 review

Lymph System Thymus o Primary lymphoid organ (no nodule) o Capsulated o Dark cortex around outside Education of thermocytes; kills thermocytes with self-antigens Epithelial reticular cells (light pink colored; looks like a starfish) form a net to hold thermocytes in the cortex o Lighter colored medulla o Stary-night appearance due to macrophages o Epithelial reticular cells also around the blood thymus barrier Want to keep blood out of the thymus because macrophages will remove the T cells that recognize any foreign antigens Thymic Medulla o Hassall’s Corpuscles 3 rd type of reticular cell Involuting thymus o Gains adipose with age Secondary lymphoid tissue o Look for Encapsulated: lymphoid nodes; spleen Unencapsulated: MALT All have nodular and diffuse regions o Diffuse region: T cells o Nodular area: B cells o Germinal center: proliferation of B cells, especially during infection Tonsils: 3 types: lingual, palatine, pharyngeal; look at epithelial layer to distinguish o Oral cavity: lingual and palatine Stratified squamous non-ketatinizin g o Back of throat: pharyngeal Pseudostratified (repiratory tract) o Identifying tonsil features Nodules Crypts (looks like empty spaces in the tissue) No capsule Lymphocytes in the oral cavity sample the outside world o Transcytosis: cell at top takes a sample and pass antigens it from cell to cell o Migration to the surface: lymphocytes can move up and infiltrate Peyer’s patch o Ilium of intestine o Identifying features: Villi

histology exam 3 review

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