December 3, 2015 - Wound Healing

Question 1

Wound Healing:

Answer 1

The restoration of surface integrity and continuity of the skin after wounding, with a tissue strength approaching normal.

Question 2

Phases of Wound Healing

Answer 2

Hemostasis

Inflammatory

Proliferative

Remodeling

Question 3

Hemostasis Phase

Answer 3

Begins at the time of the wounding

Lasts 24-48 hours

Transient vasoconstriction caused by platelets via TXA-2 (Thromboxane A2). This slows blood flow to aid in hemostasis.

Platelets form thrombus.

Clotting factors are activated.

Question 4

Inflammatory Phase

Answer 4

Vasodilation that is prostaglandin and histamine mediated

Increased blood flow supplies cells and substrates for wound healing

Macrophages and neutrophils remove necrotic tissue, debris, and bacteria

Macrophages secrete TGF-B which attracts fibroblasts

Question 5

Proliferative Phase

Answer 5

Lasts 2-4 weeks

Fibroblasts, attracted by TGF-B, move into the wound

Fibroblasts produce collagen and extracellular matrix to replace the platelet/fibrin plug

Angiogenesis occurs

Question 6

Remodeling Phase

Answer 6

During the proliferative phase, the collagen is randomly laid down. This changes in the remodeling phase.

Macrophages and fibroblasts replace the random collagen with more orderly and extensively cross-linked collagen (mostly Type I) as in normal skin.

The scar will achieve 80% of the strength of regular skin.

Question 7

Local Factors that Impede Wound Healing

Answer 7

Infection

Foreign body

Ischemia

Radiation

Trauma

Cancer

Toxins

Vascular insufficiency

Tissue edema

Question 8

Systemic Factors that Impede Wound Healing

Answer 8

Inherited disorders

Nutritional deficiency

Aging

Diabetes

Liver disease

Alcoholism

Uremia

Medications

Smoking

Psychiatric

Question 9

Smoking and Delayed Healing

Answer 9

Smoking causes vasoconstriction by nicotime, which reduces blood to the area.

Additionally, it causes atherosclerosis.

Additionally, the carbon monoxide shifts oxyhemoglobin curve to the left, impairing oxygen delivery to the tissues.

Question 10

Hypertrophic Scars

Answer 10

Histologically, increased amounts of collagen and ECM, but not organized.

Question 11

Keloid Scars

Answer 11

Histologically, whorls of fibroblasts arranged around vessels. May get worse with surgery.

Heavy genetic influence.

Often affects darker-skinned patients.