Transcript Inflammation and Tissue Repair

CHAPTER
4
Tissue: The
Living Fabric:
Part B
6/23/2012 Press Images
© Annie Leibovitz/Contact
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Inflammatory Response
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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
Epidermis
Vein
Blood clot in
incised wound
Inflammatory
chemicals
Migrating white
blood cell
Artery
1 Inflammation 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.
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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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Figure 4.12. Tissue repair of a nonextensive skin wound: regeneration and fibrosis.
Slide 2
Regenerating
epithelium
Area of
granulation
tissue
ingrowth
Fibroblast
Macrophage
Budding capillary
2 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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Figure 4.12. Tissue repair of a nonextensive skin wound: regeneration and fibrosis.
Slide 3
Regenerated
epithelium
Fibrosed area
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
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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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