Chapter 3 Tissue Development, Repair, & Unusual Growth

Germ Layers & Specialization Endoderm Ectoderm Mesoderm

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