L2.10: Tissue Repair

• • Essential physiologic process performed by the body once its integrity is compromised by wearing and tearing.
  • Enables the affected parts to regenerate its component in order to regain the structure and perform optimum function towards the overall well-being of an individual.
  • Wound healing
  • Intact physical barriers
  • INFLAMMATION - a general (nonspecific) body response that attempts to prevent further injury.
  • IMMUNE RESPONSE - extremely specific, mounts a vigorous attack against recognized invaders, including bacteria, viruses, and toxins.


  Tissue repair
• 2 major ways of tissue repair

  • regeneration
  • fibrosis (repaired with scar)
• Replacement of destroyed tissue by the same kind of cells.


  regeneration
• • Repair by dense (fibrous) connective tissue, that is, by the formation of scar tissue
  • WHICH OCCURS DEPENDS ON:
  • The type of tissue damaged
  • Severity of the injury
  • Clean cuts (incisions) heal much more successfully than ragged tears of the tissue


  fibrosis
• Note that these two (regeneration and fibrosis) occurs depending on the:

  1. Type of tissue damaged
  2. Severity of the injury.
• Events of tissue repair

  • Inflammation
  • Formation of granulation tissue
  • Regeneration and fibrosis effect permanent repair
• • Injured tissue cells release inflammatory chemicals that make the capillaries very permeable.
  • Vasodilation (dilation of blood vessels) occurs so that clotting proteins and other substances can seep into the injured area creating a clot that stops blood loss.


  Inflammation
• • Granulation Tissue: delicate pink tissue composed largely of new capillaries that grow into the damaged area from undamaged blood vessels.
  • Contains phagocytes that disposes of the blood clot
  • Has fibroblasts that produce the building blocks of collagen fibers (scar tissue) to permanently bridge the gap.
  • Rebuilding of collagen fibers.


  Formation of Granulation Tissue
• • The scab soon detaches, and the final result is a fully regenerated surface epithelium that covers an underlying area of fibrosis (the scar).
  • Composition of Scar: Dense connective tissue and is invisible, or visible as a thin white line, depending on the severity of the wound.


  Regeneration and Fibrosis Effect Permanent Repair
• • Epithelial Tissue
  • Fibrous Connective Tissues
  • Bone


  Tissues that Regenerate Easily
• skeletal muscle


  Tissues that Regenerate Poorly
• • Cardiac Muscle
  • Nervous Tissue within the brain and spinal cord.


  Tissues that are Replaced with Scar Tissue (Fibrosis)
• Modifications of cells and tissues

  • neoplasms
  • hyperplasia
  • atrophy
• Abnormal cell growths (benign or cancerous); result from lack of control of cell division.

  neoplasms
• Increase in size (of a tissue or organ); results when tissue is repeatedly and strongly stimulated or irritated.

  hyperplasia
• Decrease in size (of a tissue or organ); results when the organ is not stimulated normally.

  atrophy
• Developmental aspects of cells and tissues

  • Growth through cell division continues through puberty.
  • Cell populations exposed to friction (such as epithelium) replace lost cells throughout life.
  • Connective tissue remains mitotic and forms repair (scar) tissue.
  • With some exceptions, muscle tissue becomes amitotic by the end of puberty.
• Developmental aspects of cells and tissues

  • Nervous tissue becomes amitotic shortly after birth.
  • Neurons do not have centrioles that have a significant function in cell division, this fact is consistent with the amitotic nature of the cell.
  • They are protected from damage by the glial cell.
  • Injury can severely handicap amitotic tissues.
  • Ex: paralysis due to spinal cord injury
  • The cause of aging is unknown, but chemical and physical insults, as well as genetic programming, have been proposed as possible causes.