Surgery>>>>>Wound Healing
Question 3#

Which of the following is true regarding the fibroblastic phase of wound healing?

a. Early during wound healing, the predominant composition of the matrix is fibronectin and type II collagen
b. After complete replacement of the scar with type III collagen, the mechanical strength will equal that of uninjured tissue approximately 6 to 12 months postinjury
c. Even though the tensile strength of a wound reaches a plateau after several weeks, the tensile strength will increase over another 6 to 12 months due to fibril formation and cross-linking
d. As the scar matures, matrix metalloproteinases (MMPs) break down type I collagen and replace it with type III collagen

Correct Answer is C

Comment:

The maturation and remodeling of the scar begins during the fibroblastic phase, and is characterized by a reorganization of previously synthesized collagen. Collagen is broken down by matrix metalloproteinases (MMPs), and the net wound collagen content is the result of a balance between collagenolysis and collagen synthesis. There is a net shift toward collagen synthesis and eventually the reestablishment of extracellular matrix composed of a relatively acellular collagen- rich scar. Wound strength and mechanical integrity in the fresh wound are determined by both the quantity and quality of the newly deposited collagen. The deposition of matrix at the wound site follows a characteristic pattern: fibronectin and collagen type III constitute the early matrix scaffolding; glycosaminoglycans and proteoglycans represent the next significant matrix components; and collagen type I is the final matrix. By several weeks postinjury the amount of collagen in the wound reaches a plateau, but the tensile strength continues to increase for several more months. Fibril formation and fibril cross-linking result in decreased collagen solubility, increased strength, and increased resistance to enzymatic degradation of the collagen matrix. Fibrillin, a glycoprotein secreted by fibroblasts, is essential for the formation of elastic fibers found in connective tissue. Scar remodeling continues for many (6- 12) months postinjury, gradually resulting in a mature, avascular, and acellular scar. The mechanical strength of the scar never achieves that of the uninjured tissue.