anat patho : unit 21 - regeneration and repair Cartes | Quizlet

replacement of damaged tissue either by cells of the same lineage or by connective tissue

what is regeneration and repair?

replacement of dead cells by cells of the same lineage restoring function

what is regeneration?

Replacement of damaged tissue by connective tissue leading to scar formation.

What is repair (scarring)?

Damage to the extracellular matrix preventing true regeneration and leading to scarring only.

Why does ECM integrity matter in regeneration?

Proliferation, differentiation, apoptosis and stem cell influx.

What determines the number of cells in a tissue?

Growth factors, injury, cell death and tissue deformation.

What stimulates cell proliferation?

Local environment surrounding cells that strongly influences regeneration.

What is the role of the microenvironment?

Tissues with continuous cell replication.

What are labile tissues?

Tissues normally in resting state but capable of dividing after stimulation.

What are stable (quiescent) tissues?

Tissues composed of non-dividing cells.

What are permanent tissues?

Replacement of tissue components identical to those lost.

What is regeneration?

Compensatory growth through hypertrophy and hyperplasia restoring function without necessarily restoring original anatomy.

How does regeneration occur in mammals?

Intact extracellular matrix and tissues composed of labile or stable cells.

What conditions are necessary for regeneration?

Severe damage of parenchyma and stroma.

When does regeneration fail?

Migration and proliferation of fibroblasts and endothelial cells beginning after 24 hours.

What initiates repair?

Tissue composed of proliferating fibroblasts and neocapillaries appearing after 3-5 days.

What is granulation tissue?

Angiogenesis, fibrosis and remodeling.

What are the three major components of healing?

Formation of new blood vessels from preexisting vessels.

What is angiogenesis?

Proteolysis of basement membrane, migration and proliferation of endothelial cells, maturation and organization of capillary tubes.

What are the stages of angiogenesis?

Basic fibroblast growth factor and VEGF.

Which growth factors regulate angiogenesis?

Formation of connective tissue on the granulation tissue framework.

What is fibrosis?

PDGF, bFGF and TGF-β.

Which growth factors stimulate fibroblast migration and proliferation?

Activated endothelium, macrophages, mast cells and lymphocytes.

Which cells produce growth factors for fibrosis?

Progressive decrease in fibroblasts associated with increased ECM production.

What happens during fibrosis progression?

Pale and avascular appearance caused by involution of vessels.

What characterizes mature scar tissue?

Transition from granulation tissue to mature scar through ECM modification.

What is scar remodeling?

Zn²⁺-dependent enzymes that degrade collagen and ECM.

What are metalloproteinases?

Fibroblasts, macrophages, neutrophils, synovial cells and epithelial cells.

Which cells produce metalloproteinases?

Growth factors, cytokines and phagocytosis.

What regulates metalloproteinase synthesis?

Process where inflammatory cells first remove injury then build a framework for healing.

What are reparation stages directed toward?

Interaction between soluble growth factors and extracellular matrix.

What controls repair?

More extensive tissue loss with scar formation predominating.

What characterizes healing by secondary intention?

Greater amounts of necrotic debris, exudate and fibrin.

What differentiates secondary intention from primary intention?

More intense inflammatory response.

What inflammatory feature characterizes secondary intention?

Greater amount of granulation tissue providing scaffolding for regeneration.

Why is granulation tissue increased in secondary intention?

Larger final scar.

What is the result of secondary intention healing?

Reduction of wound size due to modified fibroblasts.

What is wound contraction?

Modified fibroblasts similar to smooth muscle cells responsible for wound contraction.

What are myofibroblasts?

Reduction of scar size by approximately 5-10%.

What is the effect of wound contraction?

Protein deficiency (especially vitamin C), immune status, leukocyte count and hormones.

What general factors influence repair?

Glucocorticoids reducing fibrosis and weakening the scar.

How do glucocorticoids affect healing?

Most important cause of delayed healing.

What local factor most delays repair?

Pressure and torsion causing separation of wound edges.

What are mechanical factors affecting healing?

Foreign material preventing normal repair.

How do foreign bodies affect healing?

Type of injured tissue and location of injury.

Which tissue characteristics influence healing?

Insufficient granulation tissue leading to wound opening and ulcers.

What is inadequate granulation tissue?

Wound opening due to poor healing.

What is wound dehiscence?

Excessive scar tissue formation.

What are hypertrophic scars and keloids?

Excessive wound contraction producing deformity.

What are contractures?