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5.5C: Deep Wound Healing

A deep wound involves the inner, deeper layers of the skin (dermis).

 

LEARNING OBJECTIVES

 

Describe the process of deep wound healing

 

KEY TAKEAWAYS

Key Points

 

  • Deep wounds are more difficult to heal, as the basement membrane and/or skin appendages ( hair follicles and sweat and oil glands) may be destroyed.
  • The healing of deep wounds may occur only at the edges of the wound, with scar tissue covering the center of the wound site.
  • Loss of physiological function is often associated with deep wounds as they do not heal correctly.
  • After healing, the tissue underlying a deep wound may be weaker than the surrounding mature tissue, making repeat injury more likely.

 

Key Terms

 

  • basement membrane: Controls the traffic of cells and molecules between the dermis and epidermis, and provides support to epidermal cells.
  • skin appendage: Skin-associated structures that serve a particular function, including sensation, contractility, lubrication, and heat loss.

Deep wounds that damage the dermis, or even the underlying muscle and fat, are more difficult to heal than shallow, epidermal-only wounds. The wound healing processes may be extended and scar tissue is likely to form due to improper re-epithelialization. 

Additionally, deep wounds are more susceptible to infection, and also to the development of systemic infection through the circulatory system, as well as   dysregulation that results in chronic wounds such as ulcers.

This image illustrates the inflammation response phase of wound healing over time. Time limits vary within faded intervals, mainly by wound size and healing conditions. The image does not include major impairments that cause chronic wounds.

 

Wound healing phases: This image illustrates the phases of wound healing. Limits vary within faded intervals, mainly by wound size and healing conditions, but the image does not include major impairments that cause chronic wounds.

 

The wound healing process for deep wounds is similar to that of shallow wounds. However, with the removal of the dermis and its associated skin appendages, re-epithelialization can only occur from the wound edge, with no contribution from the dermal compartment. 

Therefore, proper reconstitution of the epidermis is often only seen at the edge of the wound, with fibrous scar tissue—formed from the extracellular matrix (ECM) deposited during the proliferative phase—covering the rest of the wound site.

With the formation of a scar, the original physiological properties of the tissue are lost. For example scars are less flexible than skin, and do not feature sweat glands or hair follicles.

The ECM formed during wound healing may also be weaker in deep wounds, making the site susceptible to additional later wounding. The provisional ECM laid down during the proliferative phase is rich in fibronectin and collagen III that combine to allow quicker cell movement through the wound, which is very important during wound healing. 

However, the ECM of mature skin is rich in collagen I. In large, deep wounds the remodelling of a fibronectin and collagen III-rich ECM to a collagen-I rich ECM may not occur, leading to a weakening of the tissue.

 

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