Multiple choice answers
Chapter 10
1) The stages of wound healing are:
a) hyperplasia, metaplasia, neoplasia
b) haemostasis, inflammeation, proliferation, maturation#
c) heat, redness, swelling, loss of function
d) metabolism, catabolism, anabolism
The phases of wound healing
Four main phases have been identified.
Haemostasis involves wound contraction, which decreases the surface area of the wound,
thus reducing bleeding and exposure to contaminants. This process is part of the
physiological response to blood extravasation. Released platelets activate the kinin
system and release platelet-derived growth factor (PDGF), which stimulates tissue
regeneration. Chemical mediators (histamine, adenosine triphosphate and serotonin) attract
leukocytes to the injured area by a process called chemotaxis. Healing then progresses.
This phase occurs over 4-5 days and is initiated by the release of prostaglandins,
which cause vasodilatation. An inflammatory fluid (infiltrate) containing mast cells,
polymorphonuclear leukocytes and lymphocytes (Van Der Kerkhof et al., 1994) then bathes
the injured area.
The primary functions of this phase are:
To cleanse the area of debris: Monocytes enter the area and transform into activated
macrophages. These cells clear the debris through phagocytosis.
To combat potential infective organisms: Neutrophils are activated in the inflammatory
response and clear the site of contaminating organisms. This process is augmented by the
phagocytic action of the macrophages.
To initiate angiogenesis (the generation of new blood vessels0 and collagen synthesis:
Macrophages stimulate the production of angiogenic growth factors such as interleukin.
This process, augmented by the activity of mast cells, initiates endothelial division and
angiogenesis as well as the regrowth of sympathetic nerve fibres. Fibroblasts migrate to
the wound site, initiating the early stages of the next phase.
This phase of the wound healing process occurs over a variable time span and is
characterised by the formation of granulation tissue. The fibroblasts produce a framework
of collagen fibres that support and sustain the products of angiogenesis. The framework is
anchored by fibronectin and bathed in proteoglycans. The successful progress of this phase
is dependent upon the oxygen and nutrient supply.
Fibroblast activity is sensitive to oxygen supply, which in turn depends upon the
vascularity of the wound and surrounding tissues. The growth of capillary buds from
undamaged microvessels, forming a network of loops within the wound, is crucial to the
level of oxygen supply available during the proliferative phase.
Protein provides the source of the 20 amino acids present in the body (see Chapter 4).
These amino acids are described as the building blocks of organic tissue and as such are
essential for collagen synthesis, angiogenesis and cell reconstruction (Wells, 1994). If
the blood protein levels (measured by serum albumin) are low, wound healing will be
impaired.
Essential fatty acids, provided by dietary fat intake, play an important role in cell
structure and function. Dietary fat intake is also the largest source of energy, required
for wound healing, as well as providing a source of fat-soluble vitamins.
Carbohydrate, in the form of glucose, is the primary energy substrate required for
cellular metabolism. If glucose from carbohydrate is unavailable, amino acids will be
oxidised to meet the energy requirements of the wound healing process, thus depleting the
amino acids available for reconstruction and tissue repair.
Vitamin C is involved in the metabolism of many amino acids and is required for the
formation of cross-linking collagen fibres, facilitating the hydroxylation of proline and
lysine to hydroxyproline and hydroxylysine - essential components of collagen (Lewis and
Harding, 1993). Iron (as well as providing the primary component of haemoglobin, which
facilitates the transport of oxygen in the bloodstream) is a co-factor in this process.
Vitamin C also enhances wound healing by scavenging potentially harmful free radicals from
the surfaces of cells. It has been suggested that the antioxidant vitamin E interacts in
this process (Davis et al., 1991).
The B vitamins are involved in enzymatic activity (as co-factors) and are also active in
collagen cross-linkage, as is vitamin A, which also acts upon cell surface glycoproteins,
effecting epithelial cell proliferation and migration. Zinc is another co-factor in the
enzymatic activity associated with collagen and protein synthesis and cell growth. The
enzyme lysyl oxidase, instrumental in scar formation, contains copper, a trace element.
Many enzymes not only contain, but also rely on, manganese as a co-factor in collagen
synthesis, and calcium is a mediator for the enzymes involved in the remodelling of
collagen (collagenases).
Two other major processes occur concurrently within the proliferative phase of wound
healing - epithelialisation and contraction. The granulation tissue filling the wound bed
is gradually resurfaced by epithelial cells, which migrate in from the wound margins or
may regenerate as 'islands' on the wound surface. As epithelial cells regenerate and
migrate over the wound surface, their eventual contact with one another inhibits further
migration, and the epithelialisation process is complete. The process of contraction,
initiated in the inflammatory phase, is largely controlled by the activity of
myofibroblasts. These specialised fibroblasts contain actin and myosin fibrils (the
essential contractile components of muscle tissue), and their activity reduces the surface
area of the wound.
Granulation, contraction and epithelialisation mark the completion of the proliferative
phase.
This final phase in the wound healing process is concerned with the remodelling and
strengthening of the collagen fibres within the wound. The collagen produced during
earlier stages is relatively soft, type III collagen, which has been afforded structural
strength through cross-linking of the fibres. During maturation, this is replaced with
stronger type I collagen, which is organised into bundles lying at right angles to the
wound margins. This ongoing process, facilitated by the activity of fibroblasts and
characterised by a gradual reduction in vascularity of the wound site, shrinkage and
paling of the scar tissue, can continue over a number of years.
2) Secondary haemorrhage occurs when
a) the drain is removed
b) when the blood pressure rises after surgery
c) when the sutures are removed
d) there is a response to infection
d) is correct answer
Haematoma
Haematoma is the name given to a localised 'pocket' of blood and
plasma, which can become a breeding ground for bacteria.
Haemorrhage
e) Primary haemorrhage (severe blood loss during surgery) and
intermediary
Haemorrhage (severe blood loss immediately following surgery) can affect wound strength by
interfering with the function of fibroblasts. Secondary
Haemorrhage (blood loss up to 10 days postoperatively) commonly results
In haematoma formation and subsequent infection.
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