MDufilho

C H A P T E R

4

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 6/23/2012 MDufilho 2

Inflammatory Response

• Cardinal signs of acute inflammation: 1. Redness 2. Heat 3. Swelling 4. Pain (Sometimes 5. Impairment of function) 6/23/2012 MDufilho 3

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 6/23/2012 MDufilho 4

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 6/23/2012 MDufilho 5

Inflammatory Response: Edema

•  Capillary permeability  tissues

exudate

to – 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 6/23/2012 6 MDufilho

Inflammatory Response

• Clotting factors form fibrin mesh – Scaffold for repair – Isolates injured area so invaders cannot spread 6/23/2012 MDufilho 7

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 6/23/2012

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

Scab Epidermis Slide 1 Vein Blood clot in incised wound Inflammatory chemicals 1 Migrating white blood cell Inflammation sets the stage: • Severed blood vessels bleed. • Inflammatory chemicals are released.

Artery • 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 6/23/2012 MDufilho 10

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

Regenerating epithelium Area of granulation tissue ingrowth Fibroblast Macrophage Slide 2 2 Budding capillary 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 6/23/2012 MDufilho 12

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

Regenerated epithelium Fibrosed area Slide 3 3 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 6/23/2012 MDufilho 14

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  risk increased cancer 6/23/2012 15 MDufilho