Chapter 4 Part 2
Inflammation and
Tissue Repair
© Annie Leibovitz/Contact Press Images
MDufilho
Steps in Tissue Repair
• Repair can occur in two major ways:
– Regeneration: same kind of tissue replaces
destroyed tissue, so original function is restored
– Fibrosis: connective tissue replaces destroyed
tissue, and original function lost
• Step 1: Inflammation sets stage
– Release of inflammatory chemicals causes:
• Dilation of blood vessels
• Increase in blood vessel permeability
– Clotting of blood occurs
9/8/2015
MDufilho
2
Figure 4.12-1
Tissue repair of a
nonextensive skin
wound:
regeneration and
fibrosis.
Scab
Epidermis
Vein
Inflammatory
chemicals
9/8/2015
MDufilho
Blood clot in
incised wound
Migrating
white
blood cell
Artery
1 Inflammation sets the stage:
• Severed blood vessels bleed.
• Inflammatory chemicals are released by
injured tissue cells, mast cells, and others.
• 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 exposed to air
dries and forms a scab.
3
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
9/8/2015
MDufilho
4
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
9/8/2015
MDufilho
5
Steps in Tissue Repair (cont.)
• Step 2: Organization restores blood supply
– Organization begins as the blood clot is
replaced with granulation tissue (new capillaryenriched tissue)
– Epithelium begins to regenerate
– Fibroblasts produce collagen fibers to bridge the
gap until regeneration is complete
– Any debris in area is phagocytized
9/8/2015
MDufilho
6
Figure 4.12-2 Tissue repair of
a nonextensive skin wound:
regeneration and fibrosis.
Regenerating
epithelium
Area of
granulation
tissue
ingrowth
Fibroblast
Macrophage
Budding
capillary
2 Organization restores the blood supply:
9/8/2015
MDufilho
• 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.
7
Steps in Tissue Repair (cont.)
• Step 3: Regeneration and fibrosis effect
permanent repair
– The scab detaches
– Fibrous tissue matures
– Epithelium thickens and begins to resemble
adjacent tissue
– Results in a fully regenerated epithelium with
underlying scar tissue, which may or may not be
visible
9/8/2015
MDufilho
8
Figure 4.12-3
Tissue repair of
a nonextensive
skin wound:
regeneration
and fibrosis.
Regenerated epithelium
Fibrosed area
9/8/2015
MDufilho
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.
9
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
9/8/2015
MDufilho
10
Regenerative Capacity of Different Tissues
• Tissues that regenerate extremely well include:
– Epithelial tissues, bone, areolar connective
tissue, dense irregular connective tissue, bloodforming tissue
• Tissue with moderate regenerating capacity:
– Smooth muscle and dense regular connective
tissue
• Tissues with virtually no functional regenerative
capacity:
– Cardiac muscle and nervous tissue of brain and
spinal cord
9/8/2015
MDufilho
11
Clinical – Homeostatic Imbalance 4.3
• Scar tissue that forms in organs, particularly the
heart, can severely impair the function of that
organ
– May cause the organ to lose volume capacity
– May block substances from moving through
organ
– May interfere with ability of muscles to contract
or may impair nerve transmissions
9/8/2015
MDufilho
12
Clinical – Homeostatic Imbalance 4.3
• Scar adhesions may cause organs to adhere to
neighboring structures, preventing normal
functions
• Scarring can potentially cause progressive
failure of the organ, particularly the heart
9/8/2015
MDufilho
13
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
9/8/2015
MDufilho
14