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Chapter 3 Tissue Development, Repair, & Unusual Growth Germ Layers & Specialization Mesoderm Ectoderm Endoderm Specialization Developmental Aspects of Tissue Epithelial tissue -germ layers: endoderm, mesoderm, ectoderm Muscle and Connective tissue -mesoderm Nervous tissue -ectoderm Old age = decrease in mass & viabililty Tissue Repair 1. Regeneration Replacement by the same kind of cells 2. Fibrosis Repair by dense fibrous connective tissue (scar tissue) 3. Determination of method Type of tissue damaged Severity of the injury Events in Tissue Repair 1.Capillaries become very permeable Clotting proteins leak through Clot walls off injured area 2. Formation of granulation tissue Many capillaries and WBCs 3. Regeneration of surface epithelium Develops beneath scab Over the scar Regeneration of Tissues Tissues that regenerate easily - Epithelial tissue - Fibrous connective tissue and bone Tissues that regenerate poorly - Skeletal muscle Tissues that are replaced largely with scar tissue (amitotic at maturity) - Cardiac muscle - Nervous tissue within the brain and spinal cord Changes in Growth Patterns 1.Neoplasm – mitosis gone crazy; tumor • Benign – doesn’t spread; stays local • Malignant – cancerous; invades; spreads via blood – called metastisis • Carcinogens – agents that cause cancer; build up of mutations 2. Hyperplasia – temporary enlargement of localized tissues; i.e. breasts during pregnancy; can be normal or abnormal 3. Atrophy – decrease in size due to lack of use