Wound Healing 1 PDF

WOUND HEALING 1 Daniela Pereira Learning objectives 1) Understand cell injury and cell death 2) Explain the cellular response during Wound Healing Contents 1. Cell injury and cell death Part 1 2. Cellular response during wound healing...

WOUND HEALING 1 Daniela Pereira Learning objectives 1) Understand cell injury and cell death 2) Explain the cellular response during Wound Healing Contents 1. Cell injury and cell death Part 1 2. Cellular response during wound healing 3. Haemostasis 4. Inflammation Part 2 5. Proliferation and Angiogenesis 6. Matrix Remodelling 7. Tissue repair Part 3 8. Factors Impairing Healing and Repair 9. Types of Tissue Healing 1. CELL INJURY AND CELL DEATH  The intracellular milieu of cells is normally tightly regulated to maintain a stable state known as homeostasis.  Causes of cell injury: hypoxia and ischemia, toxins, infectious agents, immunologic reactions, genetic abnormalities, nutritional imbalances, physical agents and ageing.  As cells encounter physiologic stresses (such as increased workload in the heart) or potentially injurious conditions (such as nutrient deprivation), they can undergo adaptation, achieving a new steady state and preserving viability and function. TYPES OF CELL INJURY AND CELL DEATH  Depending on the nature and severity of the insult, the injuries can be reversible or irreversible.  When cells are injured they die by different mechanisms,  Unlike necrosis, which is always an indication of a pathologic process, apoptosis also occurs in healthy tissues.  Necroptosis and pyroptosis  Autophagy APOPTOSIS AND NECROSIS PYROPTOSIS AND NECROPTOSIS Ketelut-Carneiro N, Fitzgerald KA. Apoptosis, Pyroptosis, and Necroptosis—Oh My! The Many Ways a Cell Can Die. Journal of Molecular Biology. 2022 Feb 28;434(4):167378. AUTOPHAGY Autophagy is a cellular adaptation to nutrient deprivation, during which cells digest their own organelles and recycle them to provide energy and substrates. If the stress is too severe for the process to cope with, it can lead to cell death through a process called apoptosis.  NECROSIS Morphologic changes in reversible and irreversible cell injury (necrosis). (A) Normal kidney tubules with viable epithelial cells. (B) Early (reversible) ischemic injury showing surface blebs, increased eosinophilia of cytoplasm, and swelling of occasional cells. (C) Necrotic (irreversible) injury of epithelial cells, with loss of nuclei and fragmentation of cells and leakage of contents. APOPTOSIS Morphologic appearance of apoptotic cells.  Apoptotic cells (highlighted by arrows) in colonic epithelium are shown. Some preparative treatments for colonoscopy may induce apoptosis in epithelial cells, which explains the presence of dead cells in this biopsy.  Note the fragmented nuclei with condensed chromatin and the shrunken cell bodies, some with pieces falling off. 2. CELLULAR RESPONSE DURING WOUND HEALING  It is one of the most complex processes in the human body;  It involves spatial and temporal synchronisation of a variety of cell types with distinct roles in the phases of haemostasis, inflammation, proliferation and remodelling. HAEMOSTA INFLAMMATI PROLIFERATI REMODELLI SIS ON ON NG Summary  When cells are injured, the injuries can be reversible or irreversible.  If irreversible, the cells die through different mechanisms based on the nature and severity of the insult.  There are two main types of cell death, apoptosis and necrosis.  Necroptosis and pyroptosis are unusual pathways of cell death.  Autophagy happens when cells digest their own organelles to provide energy and substrates during nutrient deprivation. Severe stress can lead to cell death through apoptosis.  The cellular response during wound healing involves spatial and temporal synchronisation of a variety of cell types with distinct roles in the phases of haemostasis, inflammation, proliferation and remodelling.