Podcast
Questions and Answers
Which of the following best describes the primary function of stem cells?
Which of the following best describes the primary function of stem cells?
Which type of cells are classified as permanent cells?
Which type of cells are classified as permanent cells?
What is the significance of asymmetric replication in stem cells?
What is the significance of asymmetric replication in stem cells?
Which of the following is true regarding fibroblasts in tissue healing?
Which of the following is true regarding fibroblasts in tissue healing?
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What distinguishes the liver in terms of regeneration compared to other tissues?
What distinguishes the liver in terms of regeneration compared to other tissues?
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What is the primary characteristic of regeneration in tissue repair?
What is the primary characteristic of regeneration in tissue repair?
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What is healing by connective tissue more commonly referred to as?
What is healing by connective tissue more commonly referred to as?
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Which statement accurately describes the difference between regeneration and healing by connective tissue?
Which statement accurately describes the difference between regeneration and healing by connective tissue?
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In the context of tissue repair, what does gliosis refer to?
In the context of tissue repair, what does gliosis refer to?
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Which of the following is NOT a type of tissue repair mentioned?
Which of the following is NOT a type of tissue repair mentioned?
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Study Notes
Repair
- Repair is the replacement of damaged tissue with new healthy tissue.
Learning Objectives
- Recognize the types of repair.
- List the factors that control repair.
- Describe the mechanisms that control repair.
- Learn about stem cells and their types.
- Understand examples of repair.
- Study healing by connective tissue.
- Investigate wound healing by primary and secondary intention.
Types of Repair
- Regeneration: Replacement of damaged cells by new cells of the same type.
- Healing by connective tissue: Replacement of damaged cells by connective tissue (fibrosis or gliosis).
Cell Types
- Permanent: These cells do not regenerate after injury. Examples include neurons, cardiac muscle.
- Stable: These cells can regenerate under specific conditions. Examples include liver, kidney, pancreas mesenchymal cells (like fibroblasts), endothelial cells, smooth muscle.
- Labile: These cells continuously divide and replace lost cells. Examples include hematopoietic cells of bone marrow, surface epithelia.
Stem Cells
- Stem cells are capable of:
- Self-renewal capacity: Ability to divide and remain undifferentiated.
- Asymmetric replication: Some daughter cells remain undifferentiated after division.
- Multilineage potential or multipotent: Can differentiate into multiple cell types.
- Long-term viability.
Types of Stem Cells
- Embryonic: Totipotent stem cells.
-
Adult:
- Marrow (Hemocytoblast): Hematopoietic stem cells.
- Non-marrow (Reserve): Other stem cells.
Applications of Stem Cells in Medicine
- Treatment of diabetes, Alzheimer's.
- Replacing damaged tissues (brain, muscle, liver, bone, cartilage).
- Regrowing human teeth and hair.
Factors Affecting Repair
- Local factors: Infection, ischemia (reduced blood flow), foreign bodies, hematoma (blood collection), mechanical stress, and necrotic tissue.
- Systemic factors: Diabetes, ionizing radiation, age, malnutrition, vitamin deficiencies, drugs (steriods), and malignancy.
Mechanisms Controlling Repair
- Growth factors (EGF, FGF, PDGF, TGF alpha and beta).
- Removal of chemical factors inhibiting mitosis (chalones).
- Removal of contact inhibition.
- Cell matrix interaction.
Regeneration
- Skin:
- Epidermis - regeneration of basal cells.
- Dermis - granulation tissue → scar.
Repair of Liver after Damage
- Normal liver: Intact framework.
- Mild damage: Intact framework, regeneration.
- Massive damage: Destroyed framework, liver cirrhosis (scarring).
Liver Cirrhosis
- A condition where healthy liver tissue is replaced by scar tissue.
Repair of Bone
- Steps of bone fracture healing:
- Hematoma formation.
- Inflammation.
- Granulation tissue formation (soft callus).
- Provisional callus (woven bone).
- Hard osseous callus (lamellar bone).
- Remodeling.
- Bone marrow regeneration.
Remodeling
- Performed by osteoblasts and osteoclasts. Directed by muscle and weight-bearing stresses.
Causes of Imperfect Bone Healing
- Local factors: Inadequate immobilization, pathological fracture, soft tissue interposition, ischemia, infection.
- General factors: Old age, nutritional deficiencies, glucocorticoids, diabetes mellitus.
Healing of Nervous System
- Central nervous system (CNS): Gliosis (scarring).
- Peripheral nervous system: Regenerate.
Healing by Connective Tissue (Scar)
- Replacement of damaged tissue by granulation tissue that matures into fibrous tissue (scar).
Steps of Repair by Scar
- Hemostasis.
- Inflammation.
- Proliferation.
- Remodeling.
Proliferation Stage
- Angiogenesis (New capillaries): Arising from capillaries at edges of damaged area and new endothelial buds.
- New capillaries have no basement membrane.
- They provide nutrition to proliferating fibroblasts.
Granulation Tissue
- Composed of capillaries and fibroblasts.
- Moist, red, granular, velvety tissue.
- Fragile, bleeds easily.
- Not sensitive to infection.
- Microscopic features: Myriads of newly formed, thin-walled capillaries; active plump fibroblasts; scant collagen type I.
Maturation of Granulation Tissue (Scarring)
- Fibroblasts produce collagen fibers and ground substance.
- Fibroblasts contract (myofibroblasts), reducing the size of the lesion.
- Fibroblasts become fibrocytes.
- Remodeling into avascular, strong fibrous tissue.
Remodeling
- Rearranging collagen fibers parallelly to the surface to increase tissue strength.
Wound Healing
-
Primary intention (union): For clean surgical incisions/non-gapping wounds.
- Small blood clot, debris removal.
- Epithelialization.
- Granulation tissue formation (10-14 days).
- Scarring (Months-years).
-
Secondary intention (union): For infected, gapping crush wounds.
- Large blood clot, necrotic debris, pus.
- Granulation tissue formation.
- Epithelialization.
- Scarring (Months-years).
Complications of Wound Healing
- Excessive healing: Hypertrophic scars, keloids.
- Defective healing: Chronic ulcers, sinus, fistula, contracture, implantation cysts.
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Description
Test your knowledge on stem cells and their role in tissue repair. This quiz covers key concepts such as asymmetric replication, fibroblast function, and the differences between regeneration and healing. See how well you understand the mechanisms involved in tissue healing and regeneration!
