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Path - Tissue Repair
| Question | Answer |
|---|---|
| What is the difference between regeneration and repair? | Regeneration results in the complete restitution of lost or damaged tissue; repair may restore some original structures but can cause structural derangements. |
| This term is used to describe a pathological outcome of an inflammatory response. | organization (for example, the replacement of fibrin by connective tissue is termed organization of fibrin) |
| Define terminally differentiated cells. | Differentiated cells incapable of replication |
| An excess of stimulators or a deficiency of inhibitors that lead to uncontrolled net growth is referred to as? | cancer |
| An excess of inhibitors or a deficiency of stimulators leads to a deficient growth known as? | nonhealing wound |
| surface epithelia, the lining mucosa of all the excretory ducts of the glands, and the cells of the bone marrow and hematopoietic tissues have what in common? | they are all labile tissues |
| cells of the liver, kidneys and pancreas all have what in common? | they are all stable (quiescent) tissues |
| neurons, skeletal and cardiac muscle cells all have what in common? | they are permanent (nondividing) tissues |
| What does pluripotent mean? | they can generate all tissues of the body |
| What type of cell makes a transit amplifying cell? What does a transit amplifying cell turn into? | somatic stem cells generate transit amplifying cells, which turn into progenitor cells |
| What types of cells do the bone marrow contain, which eventually will make the blood and stromal cells? | The bone marrow contains hemopoietic stem cells (HSCs) and multipotent marrow stromal cells (or MSCs) |
| Where does the liver keep its stem/progenitor cells? What do these cells turn into? | canals of Hering, and the cells will turn into oval cells, which are bipotiental progenitors which are capable of differientiating into hepatocytes and biliary cells |
| In what two areas of the adult brain have they found neural precursor cells capable of generating neurons? | subventricular zone (SVZ) and the dentate gyrus of the hippocampus |
| Can mammals regenerate whole tissues and organs? | no |
| Why does the author say that liver cell regeneration is not true regeneration? | because the resection of tissue does not cause new growth of liver but instead triggers a process of compensatory hyperplasia in the remaining parts of the organ |
| If you resect 60% of a patients liver, about how long does it take for the remaining liver to double in size? | one month |
| What are two main growth factors/cytokines for hepatocyte replication? | hepatocyte growth factor and IL-6 |
| What are two growth inhibitors that may be involved in terminating hepatocyte replication? | transforming growth factor-B (TGF-B) and activins |
| Do intrahepatic stem or progenitor cells play a role in the compensatory growth that occurs after partial hepatectomy? | No |
| What is deposited in the damaged area in repair mechanisms that lead to scarring? | collagen and other extracellular matrix (ECM) components |
| What are the five basic features of repair by connective tissue deposition? | Inflammation, Angiogenesis, Migration and proliferation of fibroblasts, Scar formation, Connective tissue modeling |
| excess deposition of connective tissue is known as? | fibrosis |
| The relative contributions of repair and regeneration are influenced by what three main factors? | (1) the proliferative capacity of the cells of the tissue; (2) the integrity of the extracellular matrix; and (3) the resolution or chronicity of the injury and inflammation |
| What are the three phases of cutaneous wound healing? | inflammation, proliferation and maturation |
| The simplest type of cutaneous wound repair is the healing of a clean, uninfected surgical incision approximated by surgical sutures, which is known as? | healing by primary union or by first intention |
| Excisional wounds that create a more intense inflammatory reaction, extensive formation of granulation tissue, and extensive collagen deposition leading to a substantial scar is known as? | healing by secondary union or by second intention |
| When a clot is first formed to stop bleeding, it also becomes a scaffolding for migrating cells that are being attracted to the area? What cells show up within the first 24 hrs | neutrophils |
| What cells compose the granulation tissue? | fibroblasts and vascular endothelial cells |
| What is the characteristic histologic feature of granulation tissue? | the presence of new small blood vessels (angiogenesis) and the proliferation of fibroblasts |
| Explain in general the steps of angiogenesis. | increase permeability of vessels via VEGF, then degrade basement membrane with MMPs and disrupt cell contact with plasminogen activators. Then migrate endothelial cells to the stimulus, proliferate them, and mature them.Then bring in mature vessel cells. |
| WHat is the most important growth factor in angiogenesis? | vascular-endothelial growth factor (VEGF) |
| What cells stabilize newly formed weak and fragile vessels? | Stabilization requires the recruitment of pericytes and smooth muscle cells and the deposition of ECM proteins. |
| What is most important protein in all extracellular frameworks? | collagen |
| What two amino acids cannot be in collagen? What two specialized amino acids are in collagen? | cysteine or tryptophan cannot be in collagen, and the specialized proteins in collagen are hydroxyproline and hydroxylysine |
| What collagen types are fibrillar collagens? | Types 1-3, 5 and 11 |
| What collagen forms sheets and is the main component of the basement membranes? | Type 4 |
| When three chains of a particular collagen assemble to form a triple helix, this is know as what? | procollagen |
| How does procollagen become tropocollagen? | Procollagen is secreted from the cell and the aminoterminal and carboxyterminal peptides are cleaved by proteases to form the tropocollagen molecule (the basic unit of the fibrils) |
| tropocollagen spontaneously self assembles to form collagen fibrils. The formation is associated with the oxidation of lysine and hydroxylysine by what enzyme, which results in what? | lysyl oxidase, and this results in cross-linking of collagen |
| Where is vitamin C needed in collagen fibril formation? | Vitamin C is required for the hydroxylation of procollagen, a requirement that explains the inadequate wound healing in scurvy. |
| Neutrophils are replaced by what cells after 48-96 hrs? | macrophages |
| What growth factors and cytokines are involved in the migration and proliferation of fibroblasts? | growth factors PDGF, TGF-β, FGF, and the cytokines IL-1 and TNF |
| Type 3 collagen is replaced by what? | Type 1 collagen |
| What makes up a scar? | The granulation tissue scaffolding is converted into a pale, avascular scar, composed of spindle-shaped fibroblasts, dense collagen, fragments of elastic tissue, and other ECM components. |
| Wound contraction generally occurs in ______ surface wounds. | large |
| What is formed around the edge of a wound that will help it contract? | myofibroblasts |
| What are the three types of matrix metalloproteinases that aid in remodeling? What does each of them generally break down? | interstitial collagenases (collagen I-III), gelatinases (collagen and fibronectin), and stromelysins (ECM components) |
| Upon recovery of a injury, what is usual percentage of recovery of tensile strength compared to unwounded skin? | 70-80% |
| What are the three categories of pathological aspects of repair? | (1) deficient scar formation, (2) excessive formation of the repair components, and (3) formation of contractures |
| What are the two types of complications in deficient scar formation? | wound dehiscence and ulceration |
| Define hypertrophic scar and a keloid. | The accumulation of excessive amounts of collagen may give rise to a raised scar known as a hypertrophic scar. If the scar tissue grows beyond the boundaries of the original wound and does not regress, it is called a keloid |
| What is exuberant granulation? | The formation of excessive amounts of granulation tissue, which protrudes above the level of the surrounding skin and blocks re-epithelialization (this process has been called, with more literary fervor, proud flesh) |
| What does a non-healing wound mean? | A chronic or nonhealing wound is one that fails to proceed through the usual stepwise repair of the injury. In these cases the healing process is prolonged, incomplete and with lack of restoration of integrity. |
| What is the most common cause of a non-healing wound? | diabetes |
| What are the pathogenic factors for a nonhealing wound in diabetics? | 1. Peripheral neuropathy causing a lack of sensation leading to lack of awareness of trauma caused by foreign bodies, and footwear. 2. Structural deformity. 3. Peripheral arterial occlusive disease |
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