chapter 3 te

8/2/2019 Chapter 3 TE

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ssue ynam cs

Chapter 3

Patricia Relue

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Tissue replacement ratesa e .

Bone marrowmakes as many

every 2-3 days

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Difference between rate andcharacteristic time

, Rate or reaction rate, units of time-1

Reaction rate and characteristic time areinversely related Short characteristic time, fast rate

Exam le: ex onential deca . The half-lifeis the characteristic time for the process.If the rate of decay increases, the half-lifedecreases.

Example: growth rate of cells and the celldoubling time

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ynam c states o t ssue

Normal steady state function of tissue Cell production (bone marrow), transport

, ,

Tissue repair

Healing response due to wound

Tissue formation (Chapter 4) Developmental biology and morphogenesis

ounger ssues possess more organogen cpotential Stem cells

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one marrow an ematopo es s

Most rapidly replacing tissue, every2-3 days

400 billion cells/day produced

Most cells produced are highlyi erentiate an s ort- ive

T cell, B cell, erythrocyte,

neutrop , monocyte(macrophage), eosinophil, basophil,

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Villi in the smallntest ne g .

e pro uc on

occurs in the crypt

Differentiate as theymove up the crypt

Mature cells leavethe crypt

Function in theabsorption ofnutrients for ut

lumen; cell turnoverevery ~5 days, dieand slou h off

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n gure .

Basal layer hasType VII co agen

1 in 10-12 basalcells is

progenitor ce Turnover is a few

weeks

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oun ea ng v eo

http://www.youtube.com/watch?v=zZpMQ_7qiRg

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Wound healing in adult skingure .

Control of bleeding starts with rapid adhesion Agents released by platelets now Inflammatory cells Granulation tissue has

of circulating platelets to site of damage

Activated platelets secrete contents of storagegranules, spread, recruit more platelets

cause vaso a on an ncrease oo

vessel permeability Clotting cascade initiated, fibrinogencleaved by thrombin to form fibrin

m gra e o e n ury

Neutrophils begin todegranulate and die Macrophages arrive

orme ense ro as s,

macrophages, and developingvasculature)Matrix is mainly fibronectin,

Hemorrhaging is contained by blood vesselconstriction

Hemostasis Thrombosis Inflammation Granulation tissue/

p ug Fibrin plug + fibronectin holds tissuetogether and forms provisional matrix

Matrix recruits inflammatory cells

rom c rcu a on Macrophagessecrete compounds

to attract endothelial

co agen , an ya uron cacid Collagen increases the tensile

strength of the wound neovascularizationan a er ro as s an o er ce s

Epidermal cells proliferate andmigrate across the wound

ce s an ro as s,stimulate proliferation Basal layer reformsin epidermal layer

yo ro as s con rac ,pulling wound marginstogether Epidermis has stratified

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tages o woun repa r

emos as s

Thrombosis

ranu a ontissue/neovascularization

Wound appears healed

Matrix is s nthesized de raded

Collagen type III replaced by type I

Processes determine scar formation

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art age repa r gure .4

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Placement of reconstituted tissues in vivo

induces responses similar to wound healing


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ng neere woun ea ng

quare, u c ness woun ma e n s n

Porous ECM template inserted into wound Com osed of colla en I and chondroitin-6-

sulfates

Variable pore size

Variable de radation rates

Templates were tested for ability to delaywound contracture and promote dermal

Time required for the wound area todecrease by 50% was measured

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Effect of porous template onwoun ea ng gure .5

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Optimal range of pore diameter

(maximum wound healing delay)

Degradation rate was found

optimal when tuned to normalhealing rate, td ts


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Effect of pore size and degradation onwound healing rate

s oug a e e ay n woun

healing is related to improved healingcorrelates to fibroblast migration

Wound contracture normally occurs afterfibroblasts span the provisional matrix

Small pore sizes (120 m Area per volume for cell adhesion is small

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Contraction of cell-laden matricesgure .6

Exam le ofin vitrowound healing response

Cells apply tension to theECM

Tension resu ts in matrixcontraction

Circular matricesdiameter by action ofcells on matrix (diameterdecreases)

cell-matrix contraction Ability of cells to remodel

and contract matrix is

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used to engineer tissuein vitro


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Aspects of fetal and adult woundea ng responses a e .

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Insight into fetal wound healing can provide stategies for improvingadult wound healing and integration of TEMPs into the body


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Tissue dynamics as interacting cellularfate processes (Figure 3.7)

Pathology

Means for cells tocommunicate and

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coordinate their

efforts


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uest ons

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