Chapter 3

Tissue Development, Repair,

& Unusual Growth

Germ Layers & SpecializationGerm Layers & Specialization

EndodermEctoderm

Mesoderm

SpecializationSpecialization

Developmental Aspects of TissueDevelopmental 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 RepairTissue Repair1. 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 RepairEvents in Tissue Repair1.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 TissuesRegeneration 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 PatternsChanges in Growth Patterns1.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