C H A P T E R

© Annie Leibovitz/Contact Press Images

Tissue: The Living Fabric: Part B

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Inflammatory Response

• Triggered whenever body tissues injured

• Prevents spread of damaging agents

• Disposes of cell debris and pathogens

• Alerts adaptive immune system

• Sets the stage for repair

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Inflammatory Response

• Cardinal signs of acute inflammation:1. Redness

2. Heat

3. Swelling

4. Pain

(Sometimes 5. Impairment of function)

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Inflammatory Response

• Begins with chemicals released into ECF by injured tissues, immune cells, blood proteins

• Macrophages and epithelial cells of boundary tissues bear Toll-like receptors (TLRs)

• 11 types of TLRs recognize specific classes of infecting microbes

• Activated TLRs trigger release of cytokines that promote inflammation

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Inflammatory Response

• Inflammatory mediators– Histamine (from mast cells)– Kinins, prostaglandins (PGs), and

complement • Dilate local arterioles (hyperemia)

– Causes redness and heat of inflamed region

• Make capillaries leaky• Many attract leukocytes to area• Some have inflammatory roles

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Inflammatory Response: Edema

Capillary permeability exudate to tissues– Fluid containing clotting factors and

antibodies– Causes local swelling (edema)– Swelling pushes on nerve endings pain

• Pain also from bacterial toxins, prostaglandins, and kinins

– Moves foreign material into lymphatic vessels– Delivers clotting proteins and complement

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Inflammatory Response

• Clotting factors form fibrin mesh– Scaffold for repair– Isolates injured area so invaders cannot

spread

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Clinical Applications

• Benadryl (an antihistamine) – blocks receptor site (H1) for histamine receptors

• Aspirin/Ibuprofen – inhibits formation/action of prostaglandins – reduces pain and fever

Cortisone cream – inhibits release/action of inflammatory chemicals

• Naproxen – prevents formation of prostaglandins

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Figure 4.12. Tissue repair of a nonextensive skin wound: regeneration and fibrosis. Slide 1

Scab

Blood clot inincised wound

Epidermis

Vein

Inflammatorychemicals

Migrating whiteblood cell

ArteryInflammation sets the stage:• Severed blood vessels bleed. • Inflammatory chemicals are released.• Local blood vessels become more permeable, allowing white blood cells, fluid, clotting proteins, and other plasma proteins to seep into the injured area.• Clotting occurs; surface dries and forms a scab.

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Tissue Repair

• Necessary when barriers are penetrated• Cells must divide and migrate• Occurs in two major ways

– Regeneration• Same kind of tissue replaces destroyed tissue• Original function restored

– Fibrosis• Connective tissue replaces destroyed tissue• Original function lost

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Slide 2Figure 4.12. Tissue repair of a nonextensive skin wound: regeneration and fibrosis.

Regenerating epithelium

Area of granulationtissue ingrowth

Macrophage

Budding capillary

Fibroblast

Organization restores the blood supply:• The clot is replaced by granulation tissue, which restores the vascular supply.• Fibroblasts produce collagen fibers that bridge the gap.• Macrophages phagocytize dead and dying cells and other debris.• Surface epithelial cells multiply and migrate over the granulation tissue.

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Steps in Tissue Repair: Step 3

• Regeneration and fibrosis– The scab detaches– Fibrous tissue matures; epithelium thickens

and begins to resemble adjacent tissue– Results in a fully regenerated epithelium with

underlying scar tissue

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Slide 3Figure 4.12. Tissue repair of a nonextensive skin wound: regeneration and fibrosis.

Regeneratedepithelium

Fibrosed area

Regeneration and fibrosis effect permanent repair:• The fibrosed area matures and contracts; the epithelium thickens.• A fully regenerated epithelium with an underlying area of scar tissue results.

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Regenerative Capacity in Different Tissues

• Regenerate extremely well– Epithelial tissues, bone, areolar connective tissue,

dense irregular connective tissue, blood-forming tissue

• Moderate regenerating capacity– Smooth muscle and dense regular connective tissue

• Virtually no functional regenerative capacity– Cardiac muscle and nervous tissue of brain and

spinal cord– New research shows cell division does occur

• Efforts underway to coax them to regenerate better

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Aging Tissues

• Normally function well through youth and middle age if adequate diet, circulation, and infrequent wounds and infections

• Epithelia thin with increasing age so more easily breached

• Tissue repair less efficient• Bone, muscle and nervous tissues begin to

atrophy• DNA mutations possible increased cancer

risk

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