Healing and repair

===Lecture Details===
Catriona McLean; Week 9 MED1011; Pathology
===Lecture Content===
Process of repair is acute inflammation in first 24 hours, chronic inflammatory cells remove debris, new vessels repair after 1 week, proteins leak into area and act as glue, myofibroblasts start to activate after a week (produce collagen which matures over weeks and wound contracts). New epithelium develops from dermal structures and area- reepithelialises.
Healing by first intention is where there is a small gap, inflammation after 2-3 hours, redness and inflammatory cells. After 2-3 days macrophages have acted and epithelium bridges gap, clot is resorbed. 10-14 days epithelium complete and scab is loose. Week 5 there is residual redness. A scar may develop.
Second intention is when there is a significant wound gap that needs to be filled. Granulation tissue fills gap and then contracts to scar. Same process as in first intention but different level of cellularity. Granularity is due to capillaries being visible from skin. Tissue contraction occurs from myofibroblasts which contain actin. After 2 weeks epithelial cover is complete but thin. After months there is full thickness epithelium but a variable surface depression where the wound was.
Collagen is a fibrous protein between cells, provides strength to tissues, requires vitamin C. Blood only contacts collagen when tissue is wounded, and thereby collgen can sense that injury has occured. Platelets have receptors for collagen, resulting in aggregation and clotting. Polymorphs also have collagen receptors, which leads to cellular activation. Fibroblasts secrete collagen which forms a scar and is remodelled/partially resorbed in the healing process.
Outcome of healing can be infection in the wound, diabetes, poor circulation, poor immune state, dirt in the wound. Liver disease is stable tissue, is continuous injury- hepatocytes die (acute becomes chronic inflammation), repair process starts (myofibroblasts, collagen, contraction) and hepatocytes regenerate. After years liver is remodelled and cirrhosis occurs (parenchyma loss occurs and liver loses its function). In permanent tissues fibrous scars occur. Necrosis can occur.
===Readings===
====Underwood Ch 6 108-115====