Wound Healing and Tissue Repair Friday, January 31, 2003

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Wound Healing and Tissue RepairFriday, January
31, 2003
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Response to Injury
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Wound Healing and Repair
?Scenario combines 3 important processes
, because blood vessels are
open , because there has
been an injury and possible infection and
, because cellular/tissue structures
have been severed or destroyed. ?Plan of wound
healing/repair is always the same-- to close the
gap and seal it up with normal tissue or a scar.
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Wound Healing and Repair (contd)
?The ultimate result vary depending
upon --presence or absence of
__________ --the _________ of the wound (open
or closed) --the ________ supply --the
amount of dead tissue to be eliminated --the
type of wounded tissue, and many other factors!
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Healing and Repair- Distinguishing Them
?Following tissue damage and/or loss from any
cause, including damage due to the inflammatory
process, there may be a number of different
solutions to the problem ?
- Dead cellular material and debris are
removed by phagocytosis (macrophages) and tissue
is left with its original architecture. ?
- Lost tissue is replaced by
proliferation of cells of the same type, which
reconstruct the normal architecture.
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Healing and Repair- Distinguishing Them
?Repair- A _______ ________ that is produced
from granulation tissue replaces lost tissue.
?All of these processes may occur in the same
tissue, and begin as soon as there is significant
tissue damage. ?Healing reactions do wait
for inflammation or other damaging processes to
subside, but take place at the same ______.
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The Outcome of Healing and Repair
?The outcome in any situation depends on which of
the three processes predominates, and depends on
a number of factors Resolution- --This tends to
occur when there is tissue
destruction. --A good example is lobar
____________. In the earlier stages of lobar
pneumonia the alveolar spaces fill with pus but
the alveolar walls remain intact. --If the
infecting organism is then the
purulent material may be completely scavenged by
macrophages, leaving the original lung structure
intact.
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The Outcome of Healing and Repair (contd)
Regeneration- The cells of the body are divided
into 3 groups 1. Continuously dividing (also
called cells) ?follow cell cycle
from one ________ to the next, and continue to
proliferate, replacing cells that are
continuously destroyed.
--surface such as skin, oral
cavity, vagina and cervix lining mucosa of
all of the excretory ducts --columnar
of the GI tract, uterus, and
fallopian tubes the transitional epithelium of
the urinary tract and cells of the splenic,
lymphoid and tissues.
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The Outcome of Healing and Repair (contd)
2. Quiescent (or )
cells ?usually demonstrate a low normal level of
replication. These cells can undergo rapid
division in response to a variety of stimuli and
help reconstitute the tissue or origin.
--this would be cells
(functional) in virtually all of the glandular
organs of the body, liver, kidney, and
pancreas -- cells
(stromal) such as fibroblasts and smooth muscle
cells and vascular endothelial cells.
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The Outcome of Healing and Repair (contd)
3. Non-dividing ( )
cells ?have the cell cycle and cannot
undergo mitotic division in postnatal
life. --the nerve cells and cardiac muscle
cells.
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Cell Groups Based on Capacity to Regenerate
?Cells are usually classified into these three
groups depending on their capacity for
______________ --Labile (continuously dividing)
cells are those that normally have a high rate of
loss and replacement and therefore have a ___
capacity for regeneration. --Stable
(quiescent) cells do not normally proliferate to
a significant extent but can be __________ to do
so after damage. --Permanent (non-dividing)
cells are unable to divide after initial
development and therefore cannot ___________.
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Tissue Architecture

• structures are easier to reconstruct
  following damage than ________
• ones, e.g., a flat surface such as epidermis
  regenerates very successfully, but dermal sweat
  glands do not.
• ?An imperfect attempt at regeneration of tissue
  architecture may have important clinical
  consequences
• --chronic inflammatory disease
  regenerative proliferation of hepatocytes is
  vigorous
• --damage to the connective tissue framework
  results in an abnormal nodular architecture-
  
• --abnormal liver architecture can lead to portal
  hypertension that may result in death due to
  uncontrollable .

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Steps to Achieving Repair or Regeneration
Amount of Tissue Loss- ?_________ implies that
there are cells left to regenerate. ?If there
is large loss of area of tissue, it will heal by
_____ formation rather than regeneration.
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Steps to Achieving Repair or Regeneration
Repair- ?The repair process results in formation
of a fibrous scar from
tissue. ?The steps in this process are
as follows --Phagocytosis of necrotic debris by
__________. --Proliferation of blood vessel
_______ cells and _________ at the edges of the
damaged area.
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Steps to Achieving Repair or Regeneration
--Endothelial cells grow into the damaged area,
initially as solid buds from adjacent blood
vessels, to form an abundant network of delicate,
thin-walled ___________. --Fibroblasts migrate
into the damaged area along with the capillaries
to form a loose connective tissue framework.
This delicate fibrovascular tissue is __________
tissue. --The new capillary vessels establish a
blood circulation in the healing area and
________ towards arterial and venous types as
necessary.
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Steps to Achieving Repair or Regeneration
?The steps in this process are as follows
(continues) --Fibroblasts produce ________,
giving the healing tissue mechanical strength.
--Eventually a mature _____ consisting almost
entirely of dense collagen is produced.
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Histology of Wound Healing and Repair
At high magnification, granulation tissue has
capillaries, fibroblasts, and a variable amount
of ____________ cells (mostly mononuclear).
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Gross of Wound Healing and Repair
Chronic inflammation can be seen in conjunction
with some degree of . Here,
chronic inflammation of the bronchi has led to
dilation and scarring with increased tan to white
__________ tissue.
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Histology of Wound Healing and Repair
The _____ result of inflammation can be scarring.
The alveolar walls are thickened and filled with
pink collagen following an autoimmune disease
lasting for decades.
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Primary and Secondary Intention
Wound Healing- ?Time course of healing by repair
and the amount of scar tissue formed depend on
factors such as the of tissue
damage, of persisting infection,
inflammation, etc. ?Simple, rapid process of
healing in a clean skin wound which has been
closed promptly and where tissue damage is
minimal (e.g., surgical incision) is termed
healing by or primary intention.
?Epidermis regenerates across the gap quickly
and successfully, the volume of tissue into which
granulation tissue has to grow is small, and the
amount of fibrous scar produced is minimal.
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Histology of Wound Healing and Repair
This is a healing biopsy site on skin a _____
after the excision. The skin surface has
re-epithelialized, and below this is granulation
tissue with small capillaries and fibroblasts
forming collagen. After a _____, just a small
collagenous scar will remain.
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Histology of Wound Healing and Repair
This is a healing biopsy site on skin a _____
after the excision. The skin surface has
re-epithelialized, and below this is granulation
tissue with small capillaries and fibroblasts
forming collagen. After a _____, just a small
collagenous scar will remain.
?Healing of an _____ wound where there is
significant tissue loss or where there is ongoing
tissue damage from infection is termed healing
by intention.
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Outcome of Healing and Repair
A recently severely burnt hand. Much of the skin
has been completely destroyed and the underlying
tissue is undergoing repair. The damaged area is
being replaced by _______ _____, which will
undergo further organization to form dense
________ scar.
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Outcome of Healing and Repair
A recently severely burnt hand. Much of the skin
has been completely destroyed and the underlying
tissue is undergoing repair. The damaged area is
being replaced by _______ _____, which will
undergo further organization to form dense
________ scar.
?In this situation, the amount of granulation
tissue formed is substantial, scar contraction
greater, and re-epithelialization less complete.
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Granulomatous Inflammation (Chronic
Inflammation) vs. Granulation Tissue (Wound
Healing/Tissue Repair)
This photomicrograph shows several thin-walled
capillary blood vessels growing into damaged
tissue associated with a perforation of the large
intestine. Red blood cells can be seen within
the vessels and also extravasated in the tissue.
The elongated cells with plump, oval nuclei and
pink cytoplasm are fibroblasts.
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Granulation Tissue (Wound Healing/Tissue Repair)
This area of granulation tissue contains chronic
inflammatory cells, illustrating that
inflammation and healing can happen concurrently.
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Granulation Tissue (Wound Healing/Tissue Repair)
The wall of an abscess has granulation tissue,
shown on the left. The purulent exudate with
some hemorrhage is shown on the right in the
abscess center.