Tissue Renewal and Repair Flashcards
What is parenchyma?
Functional cellular components of the tissue or organ
What is scarring?
Replacement of epithelium/parenchyma with CT
What is the bodies two responses to tissue loss?
Repair by regeneration or scarring
What is fibrosis?
An abnormal deposit of collagen and other ECM in the process of repair
What happens in a deep skin wound?
Stromal cells proliferate and predominate the parenchymal cells
When can regeneration occur?
As long as parenchyma can still proliferate and sufficient stromal tissue can provide support
What can chronic inflammation cause?
Fibrosis due to periodic cell loss
What are the primary inflammatory cells?
Polymorphonucleocytes (neutrophils) macrophages
What is granulation tissue?
Initial phase of stromal repair response highly vascular loose CT
What are three types of tissues?
Labile
Stabile
Permanent
What are labile tissues?
Continuously dividing cells
What are stabile tissues?
Quiescent cells that are in the Go stage and have limited proliferation can be stimulated to enter G1 stage
What are permanent tissues?
Post-mitotic cells
What are the 8 processes of wound healing/repair?
Maintain hemostasis Inflammatory response Proliferation and migration of parenchyma cells Angiogenesis Formation of granulation tissue Connective tissue remodeling Wound contraction Acquisition of increasing wound strength
What is needed for hemostasis?
Fibrinogen->Fibrin (scab/eschar formation)
What is provisional matrix?
Temporary loose CT
Type III collagen
What is involved in granulation tissue?
Angiogenesis
Mononuclear inflammatory cells
Type III collagen
What are matrix metalloproteinases (MMPs)?
Enzymes that help degrade extracellular proteins
How is the ECM remodeled?
Activation of MMPs and signaling of fibroblasts to deposit new proteins
What signals the activation of fibroblasts?
TGF-Beta
What causes wound contraction?
Myofibroblasts
How is wound tensile strength increased?
Type 1 collagen (mature scar) is laid down
What is granulation tissue as apposed to fibrosis?
Immature scar vs a mature scar
What is healing by primary intent?
Approximating the wound edges to minimize scarring and heal quickly; typically not as deep of a wound
What is healing by secondary intent?
Allowing the wound to heal by granulomatous tissue; grows from the bottom up and will leave a scar healing slowly; typically deep wounds
What is patchy loss of cells in the heart cause?
Interstitial fibrosis
What does diffuse loss of cells in the heart cause?
Myocardial infarction
How long does it take for granulation tissue to mature?
7 days
When does a scar gain maximum tensile strength?
14-21 days
What can occur with 14 days of a MI?
An aneurysm may form due to weak scar formation if enough pressure is applied
What is the difference between PNS and CNS axons?
CNS axons cannot regenerate
PNS axons can elongate and regenerate
What accomplishes scarring in the CNS?
Glial cells via gliosis
What accomplishes scarring in the PNS?
Fibroblasts via fibrosis
What is hypertrophic scarring?
Excessive scar formation due to excessive amounts of collage resulting in a raised scar?
What is a keloid?
Disorganized excessive scarring; excessive collagen in dermis that overshoots the bounds of the injury
What is contracture?
Deformity of wounded tissue and surrounding structures
How can contracture occur in somatic and visceral body parts?
Somatic: where skin is too close to tendons the tendons can become caught in contracting wounds
Visceral: can cause bowel strictures/obstruction
What collagen is found in a mature scar?
Type I collagen
What is a pyrogenic granuloma?
Inflammatory lesion with exuberant overgrowth of granulation tissue; neoplastic (often in gingiva of pregnant women)
What is proud flesh?
Granulation of tissue that extends above the epithelial surface and inhibits re-epithelialization
What is a desmoid?
Fibrosis following injury or surgical incision within soft tissue (neoplastic)