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Healing and repair
1. Tissue repair involves regeneration of injured tissue or replacement by connective tissue scarring. It involves cell proliferation and interaction between cells and the extracellular matrix. 2. Tissues are divided into continuously dividing, stable, and permanent groups based on their ability to proliferate. Continuously dividing tissues like skin regenerate easily while permanent tissues like neurons cannot regenerate after injury. 3. Growth factors and the extracellular matrix play important roles in tissue repair by stimulating cell growth and movement. Repair occurs through regeneration in labile tissues and scarring in others when injury is too severe for regeneration.
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Introduction to healing processes, including tissue repair types: regeneration and scarring.
Introduction to healing processes, including tissue repair types: regeneration and scarring.
Classification of body tissues into continuously dividing, stable, and permanent tissues regarding repair ability.
Importance of growth factors in stimulating proliferation; ECM regulates cellular functions in repair.
Processes of regeneration in labile and stable tissues, and the formation and remodeling of scars.
Introduction to healing processes, including tissue repair types: regeneration and scarring.
Four phases of wound healing: hemostasis, inflammation, granulation, and remodeling; timeline of events.
Details of first intention healing for small wounds with minimal scarring and quick recovery timeline.
Explanation of second intention healing for larger wounds, emphasizing fibrosis and increased healing time.
Impact of local and general factors including infections, age, health, and dietary deficiencies on healing.
Potential complications such as insufficient or excessive fibrosis, leading to various skin deformities.
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Healing and repair
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- 3. • Tissue repair:restoration of tissue architecture and function after an injury • Occurs in two ways: • Regeneration of injured tissue. • Replacement by connective tissue (scarring)
- 4. • Usually, tissuerepair involves both processes • Involves cell proliferation, and interaction between cells and extracellular matrix.
- 5. • Many cellsproliferate during tissue repair: • Injured tissue remnants. • Vascular endothelial cells • Fibroblasts
- 6. Tissues of thebody are divided into three groups: •Continuously dividing (labile) tissues. •Stable tissues. •Permanent tissues
- 7. •Continuously dividing (labile)tissues •Cells are continuously proliferating. •Can easily regenerate after injury •Contain a pool of stem cells •Examples: bone marrow, skin, GIT epithelium.
- 8. Stem cells inskin
- 9. Stem cells inGI epithelium
- 10. •Stable tissues •Cells havelimited ability to proliferate. •Limited ability to regenerate (except liver!) •Normally in G0, but can proliferate if injured. •Examples: liver, kidney, pancreas…
- 11. • Permeant tissue •Cells can't proliferate • Can't regenerate (So injury always lead to scar) • Examples: Neurons, Cardiac muscles
- 12. GROWTH FACTORS •Very importantin tissue repair. •Actions: •Stimulate cell division and proliferation. •Promote cell survival.
- 13. THE EXTRACELLULAR MATRIX •ECMis the network that surrounds cells. It is two forms: interstitial matrix and basement membrane. •ECM regulates proliferation, movement, and differentiation of the cells living in it.
- 14. REGENERATION •Occurs all thetime in labile tissues •Cells are constantly being lost and replaced •If demand increases, supply increases easily
- 15. •Occurs in limitedform in stable tissues •Remove one kidney: the other one undergoes hypertrophy and hyperplasia •Remove half of the liver: it will grow back
- 16. SCARRING •If injury issevere, regeneration can’t happen •So, fibrosis (a scar) replaces the injured tissue
- 17. •Four components tothis process: •New vessel formation (Angiogenesis). •Fibroblast proliferation. •Synthesis of collagen (Scar formation). •Remodeling of the scar.
- 18. •By 24 hours: •Endothelialcells start proliferating •Fibroblasts emigrate •By 3-5 days: •Granulation tissue present (blood vessels+ fibroblasts). •Weeks later: •Dense fibrosis (scar) •Scar is remodeled over time
- 21. Introduction to woundhealing • Healing is a complex and dynamic process of restoring cellular structures and tissue layers. • The adult wound healing process can be divided into 4 distinct phases: • The homeostasis phase • the inflammatory phase • the proliferative phase • the remodeling phase.
- 22. Sequence of eventsin healing Initial phase - Hemostasis • Following vasoconstriction, platelets adhere to damaged endothelium and discharge adenosine diphosphate (ADP), promoting thrombocyte clumping, which dams the Wound
- 23. • The inflammatoryphase is initiated by the release of numerous cytokines by platelets. • Fibrinogen is cleaved into fibrin and the framework for completion of the coagulation process is formed.
- 24. Second phase -Inflammation • Within the first 6-8 hours • polymorph nuclear leukocytes (PMNs) “cleanse” the wound, clearing it of debris , monocytes also exude from the vessels. These are termed macrophages. The macrophages continue the cleansing process and manufacture various growth factors during days 3-4.
- 25. Third phase -Granulation sub phases are: fibroplasia -matrix deposition - angiogenesis - and re-epithelialization • In days 5-7, fibroblasts have migrated into the wound, laying down new collagen of the subtypes I and III
- 26. • Angiogenesis .The formation of new vasculature requires migration, mitosis, and maturation of endothelial cells • Re-epithelization occurs with the migration of cells from the periphery of the wound . Division of peripheral cells occurs in hours 48-72, resulting in a thin epithelial cell layer, which bridges the wound.
- 27. Fourth phase -Remodeling After the third week, the wound undergoes constant alterations, known as remodeling, • This can last for years after the initial injury occurred. Collagen is degraded and deposited in an equilibrium-producing fashion
- 28. • Contraction ofthe wound is an ongoing process resulting in part from the proliferation of the specialized fibroblasts termed myofibroblasts, which resemble contractile smooth muscle cells.
- 29. 1. SKIN WOUNDHEALING • First intention • Second intention
- 31. Healing by FirstIntention •Occurs in small wounds that close easily •Epithelial regeneration predominates over fibrosis •Healing is fast, with minimal scarring/infection •Example: Well-approximated surgical incisions
- 32. Healing by FirstIntention: Timeline • By 24 hours • Clot forms • Neutrophils come in • Epithelium begins to regenerate
- 33. • By 3-7days • Macrophages come in • Granulation tissue is formed New blood vessels Fibroblasts • Collagen begins to bridge incision • Epithelium increases in thickness
- 34. • Weeks later •Granulation tissue gone • Collagen is remodeled • Epidermis is full and mature, but without dermal appendages.
- 38. Healing by SecondIntention • Occurs in larger wounds that have gaps between wound margins • Fibrosis predominates over epithelial regeneration • Healing is slower, with more inflammation and granulation tissue formation, and more scarring
- 39. • Examples: • MyocardialInfarction • Large burns and ulcers
- 42. Skin ulcer: largegap between edges
- 43. FACTORS AFFECTING WOUNDHEALING Local factors • Infection is the single most important cause of delay in healing. • Mechanical factors, as early motion of wounds, can delay healing. • Foreign bodies, such as fragments of steel, glass, or even bone
- 44. • Size, location,and type of wound influence healing. Wounds in richly vascularized areas, such as the face, heal faster than those in poorly vascularized
- 45. General Factors • Age •General state of health • chronic diseases e.g. diabetes, rheumatoid arthritis etc. • Drugs (steroids) and hormones • General cardiovascular status
- 46. • General dietarydeficiencies e.g. protein • Specific dietary deficiencies • Vitamin C • sulphur-containing amino acids
- 47. Complications of Repair •Insufficient fibrosis: • hernia; ulceration • Excessive fibrosis: • Cosmetic scarring; hypertrophic scars; keloid
- 48. • Excessive contraction: •Limitation of joint movement (Contractures); obstruction of tubes & channels (Strictures)
- 49.