The physiology of wound healing Flashcards
What are the different aspects to the physiology of wound healing?
Vascular response, inflammatory response, proliferation and maturation. These aspects all overlap
What is the vascular response in wound healing?
Trauma results in bleeding -> vasoconstriction for 5-10 minutes -> clotting process -> formation of a fibrin mesh
What is the aim of acute vasoconstriction in wound healing?
Reduce blood loss
When does the clotting process in wound healing start?
When blood is exposed in the air
What do blood and serous fluid do during wound healing?
Cleanse the wound of surface contaminants
How do the platelets and fibrin mesh interact in wound healing?
The platelets get trapped in the fibrin mesh and release inflammatory mediators e.g. prostaglandins and histamine
What happens to the vessels adjacent to the injury?
Vasodilation and increased permeability
How long after injury does vasodilation in the adjacent areas peak?
Twenty minutes
What is the role of neutrophils in wound healing?
They release free radicals and proteases and are bactericidal
What is the role of macrophages in wound healing?
They ingest dead tissue and release cytokines that recruit lymphocytes and fibroblasts
When are lymphocytes released after injury and what do they do?
Enter the wound after 72 hours and secrete chemotactic factors for fibroblasts
How long does the inflammatory response last in clean wounds?
Up to 7 days
When does the proliferative stage begin?
Two or three days after the event, as the inflammatory response is ending
How long does the proliferative stage take?
Can last up to two to four weeks
What do fibroblasts secrete during the proliferative stage?
Collagen and glycosmainoglycans
What happens during the proliferative stage?
New connective tissue (collagen) fills the wound during this stage - this continues rapidly for 2-3 weeks then it levels off
What things during the proliferative stage reduce wound size?
Physiological processes such as granulation (angiogenesis), epithelialisation and contraction reduce wound size
When does maturation begin?
Begins approximately when collagen production levels off - usually twenty days after injury
How long can maturation last for?
It can last for months or even years, depending on wound size and whether it was initially left open or closed.
When does primary intention occur?
Can only be achieved if little or no tissue loss; wound edges need to be directly apposed to each other; results in linear scarring (example: surgical wounds)
When does secondary intention occur?
Would edges are not opposed (ulcer); the wound is allowed to granulate - granulation may cause a broader scar (example: pretibial laceration with skin loss)
How does secondary intention work?
Epithelialisation occurs from the edge, from hair follicles remnants in the base in the wounds
When does tertiary intention work?
Wound is purposely left open (e.g. infection); initially cleaned, debrided and observed; later surgically closed
What are general social barriers to healing?
Elderly, diabetes, malnutrition, malignancy, renal or hepatic failure, drugs, immunosuppressive diseases, vitamin deficiencies.
What are local factors that are barriers to healing?
Site, infection, oedema, vascular insufficiency, previous radiotherapy
