Tissue repair Quiz 2

Tissue Repair and Healing Processes

• Tissue repair can occur through regeneration or scarring, with factors such as persistent infection, diabetes, and poor blood flow impairing the process.
• The cell cycle has phases like S, G1, G2, and G0, and cells are categorized as labile, stable, or permanent based on their proliferative capacity.
• Labile cells, like those in the bone marrow and epithelium, continually divide throughout life.
• Stable cells are normally quiescent, re-entering the cell cycle only under certain conditions, such as healing, and include fibroblasts and vascular endothelial cells.
• Permanent cells, like the bulk of cardiac muscle cells and neurons, cannot undergo mitosis postnatally.
• Regeneration requires specific conditions, such as the tissue being composed of labile or stable cells and the presence of surviving cells capable of division.
• Scarring occurs in tissues incapable of regeneration due to factors like permanent cell composition, lack of surviving tissue cells, or disrupted connective tissue framework.
• Tissue repair mechanisms involve both regeneration and scar formation, with mild injuries repaired by regeneration and more severe injuries by scar formation.
• Healing by scarring involves inflammation, angiogenesis, fibroblast migration and proliferation, and deposition of fibrous tissue into a mature scar.
• Growth factors like vascular endothelial growth factors (VEGFs), fibroblast growth factors (FGFs), platelet-derived growth factor (PDGF), and transforming growth factor-B (TGF-B) play key roles in repair and regeneration.
• The extracellular matrix (ECM) supports cells, contains fluid transporting nutrients, and consists of macromolecules like collagen, elastin, fibronectin, laminin, integrins, and proteoglycans.
• The provided link leads to a Khan Academy video on tissue repair and healing processes.

Tissue Repair and Healing Processes

• Tissue repair can occur through regeneration or scarring, with factors such as persistent infection, diabetes, and poor blood flow impairing the process.
• The cell cycle has phases like S, G1, G2, and G0, and cells are categorized as labile, stable, or permanent based on their proliferative capacity.
• Labile cells, like those in the bone marrow and epithelium, continually divide throughout life.
• Stable cells are normally quiescent, re-entering the cell cycle only under certain conditions, such as healing, and include fibroblasts and vascular endothelial cells.
• Permanent cells, like the bulk of cardiac muscle cells and neurons, cannot undergo mitosis postnatally.
• Regeneration requires specific conditions, such as the tissue being composed of labile or stable cells and the presence of surviving cells capable of division.
• Scarring occurs in tissues incapable of regeneration due to factors like permanent cell composition, lack of surviving tissue cells, or disrupted connective tissue framework.
• Tissue repair mechanisms involve both regeneration and scar formation, with mild injuries repaired by regeneration and more severe injuries by scar formation.
• Healing by scarring involves inflammation, angiogenesis, fibroblast migration and proliferation, and deposition of fibrous tissue into a mature scar.
• Growth factors like vascular endothelial growth factors (VEGFs), fibroblast growth factors (FGFs), platelet-derived growth factor (PDGF), and transforming growth factor-B (TGF-B) play key roles in repair and regeneration.
• The extracellular matrix (ECM) supports cells, contains fluid transporting nutrients, and consists of macromolecules like collagen, elastin, fibronectin, laminin, integrins, and proteoglycans.
• The provided link leads to a Khan Academy video on tissue repair and healing processes.

Understanding Granulation Tissue and Scar Formation

• Granulation tissue is formed after tissue injury, characterized by angiogenesis and fibroblast proliferation, and has a pink, soft, granular appearance.
• The granulation tissue contains newly formed small blood vessels originating from preexisting blood vessels and immature vessels with leaky interendothelial junctions, causing edema.
• Fibroblasts in granulation tissue synthesize Type III collagen, and myofibroblasts are important in wound contraction.
• Weeks to months after injury, granulation tissue transforms into a mature scar, with an increase in collagen and other extracellular matrix proteins, and a decrease in fibroblasts and vascularity.
• Scar formation involves injury-induced inflammation, vascularized granulation tissue, and deposition of extracellular matrix to form the scar.
• Cutaneous wound healing by first intention involves regeneration with wound edges close together, while healing by second intention involves more scarring and less regeneration with farther apart wound edges.
• Progenitor cells have unlimited proliferative capacity and undergo asymmetric replication, retaining self-renewing capacity while the other cell enters a differentiation pathway.
• Embryonic stem cells are pluripotent and can be isolated from blastocysts, potentially used for therapeutic cloning and producing knockout mice.
• Adult stem cells have a more restricted differentiation capacity and are generally lineage-specific, but stem cells with broad differentiation potential have been found in various adult tissues.
• Stem cell niches are specific locations in tissues where stem cells are found, including crypts in the intestine, hair follicle bulge, and canals of Hering in the liver.
• The text includes references to authoritative sources such as Kumar et al.'s "Robbins Basic Pathology" and Kumar et al.'s "Robbins and Cotran Pathologic Basis of Disease."
• The text also acknowledges special thanks to Paul Murphy, M.D., from the Department of Pathology at the University of Kentucky, and lists additional resources such as WebPath, Pathoma, and Access Medicine.