1.2 Wound repair

the three parts of tissue repair:

• cell and tissue regen

• scar formation

• factors influencing repair

• restoration of tissue architecture and function after injury

• occurs by regen (midl or superficial injury) or scar formation (severe injury)

what is tissue repair?

• proliferation of residual cells that retain capacity to divide and by replacement from stem cells

• typical response in organs w rapidly dividing cells i.e skin, mucosa, liver

what is regeneration?

• repair occurs by laying down CT

• fibrous tissue cannot perform function of previous tissue but provides stability

• fibrosis= deposition of collagen in organs after chronic inflam (excess)

infection or injury leads to injury site the inflammation and then formation of granulation tissue then scar

what is scarring?

tissue that is replaced by scar tissue

granulation tissue

what does granulation tissue replace?

inflammation cells

what does regenerative capacity depend on?

ability of tissue to regenerate

what was the significance of varicose veins?

vein that has lost elasticity so it is expanded

re-canalization: reopen

three types of proliferative tissues?

• labile tissue: continuous division

• stable tissue: quiescent cells w minimal replicative activity

• permanent tissue: terminally differentiated

• high turnover rate

• high regenerative capacity

• ex: squamous, glandular, and GI epithelium; bone marrow

  • skin, oral mucosa, genitals

labile cells

• low turnover rate

• can proliferate rapidly when called upon

• ex: fibroblasts, osteoblasts, liver, kidney, endothelial cells

  • “solid organs”

stable cells

• cannot divide

• cannot regen

• heal with scar tissue

• ex: neurons and cardiac cells; tooth enamel

  • why damage to these can be so detrimental; necrosis here is final

permanent cells

best but uncommon possible outcome of acute inflam

regeneration: acute inflam resolves and damaged epithelial cells regen

five factors that favor regen:

• tissue w regen capacity

• minimal cell death fast elimination of agent

• fast removal of debris

• adequate drainage

T or F: regen restores normal structure and function without scarring (regen)

T

T or F: acute inflam exudate is removed by liquefaction and phagocytosis (regen)

T

T or F: support stroma does not have to be in tact for regen

F: stroma must be in tact

T or F: damaged cells must be able to regen for regen to happen

T (duh)

how does repair by CT deposition occur?

1. angiogenesis

2. granulation tissue development: pink granular appearance

3. remodel of CT

granulation tissue

proliferation of capillaries, endothelial cels, inflammatory cells, fibroblasts, CT

granulomas

• epithelioid histiocytes

• multi-nucleated giant cells and lymphocytes

• chronic inflammation

what conditions have granuloma in their name but are not granulomas? they have granular tissue?

growth/swelling = granuloma but granulation tissue

• periapical granuloma

• pyogenic granuloma

• peripheral giant cell granuloma

• central giant cell granuloma

• traumatic ulcerative granuloma

what helps with blood vessel formation and lines walls?

pericyte

mechanism of repair by CT deposition

• deposition of CT

  • fibroblast migrate, proliferate, and deposit ECM: TGF beta (cytokine for Ct synthesis and deposition of CT proteins)

• remodel CT: depends on synthesis and degradation of proteins

• infection

• diabetes: abnormal wound healing (abs can help)

• nutrition: vit C deficiency

• glucocorticoids: steroids weaken scar formation by inhibiting TGFβ (use for keloids)

• mechanical variables: no undo strain or stress

  • place suture along normal lines of tension, medial to lateral rather than anterior to posterior

• poor perfusion: poor vascular flow i.e arterial sclerosis

• foreign bodies: suture can cause foreign body rnx

• type and extent of injury

• location of injury

factors that influence repair

primary vs secondary healing

• Primary healing occurs when a wound heals without infection and the edges are close together (suture)

• Secondary healing occurs when a wound is left open to heal naturally

primary intention is

healing of closely opposed surfaces

• epithelial regen is principal mechanism of repair

• small scar with minimal wound contraction

days of healing by primary intention

differences in healing from second intention compared to first

• larger clot

• more intense inflam

• more granulation tissue

• wound contraction: w/in 6 weeks large wounds reduced 5-10% their original size

do sutured wounds regain strength of normal skin?

NO

• regain 10% when suture removed at 1 week

• reach max of 70-80% in 3 months

parenchymal organs:

liver, lungs, kidney, spleen, adrenal glands

tissue repair for parenchymal organs:

• collagen deposition normal in wound healing

• excessive deposition of collagen or ECM = fibrosis

amalgam tattoo

benign, flat, discolored area in the mouth caused by amalgam particles from a dental filling

• during procedure or removal

• gingiva, bucal mucosa, tongue

tissue repair for brain damage

• repaired through proliferation of astrocytes (brain support cells) not fibroblasts

• necrotic tissue replaced by fluid

• glial scar/astrocyte gliosis: cystic lesion surrounded by compacted glial fibers produced by astrocytes

tissue repair for bone damage

• collagenous scarring insufficient to repair bone

• fractures repair through organization, granulation tissue formation, and fibroblasts in-growth with osteoblast proliferation

define callus

mixture of fibrous granulation tissue and developing new bone

what is wound dehiscence?

surgical complication that occurs when a surgical incision opens or separates; often after abdominal surgery due to increased pressure

wound abnormality

what are hypertrophic scars and keloids?

prominent raised scars resulting from excess production of ECM

steps to fibrosis