Surgery>>>>>Wound Healing
Question 7#

Which of the following is FALSE regarding healing of full-thickness injuries of the GI tract?

a. Serosal healing is essential to form a water-tight barrier to the lumen of the bowel
b. Extraperitoneal segments of bowel that lack serosa have higher rates of anastomotic failure
c. There is an early decrease in marginal strength due to an imbalance of greater collagenolysis versus collagen synthesis
d. Collagen synthesis is done by fibroblast and smooth muscle cells
e. The greatest tensile strength of the GI tract is provided by the serosa

Correct Answer is E

Comment:

The submucosa lies radially and circumferentially outside of these layers, is composed of abundant collagenous and elastic fibers, and supports neural and vascular structures. The submucosa is the layer that imparts the greatest tensile strength and greatest suture-holding capacity, a characteristic that should be kept in mind during surgical repair of the GI tract. Additionally, serosal healing is essential for quickly achieving a watertight seal from the luminal side of the bowel. The importance of the serosa is underscored by the significantly higher rates of anastomotic failure observed clinically in segments of bowel that are extraperitoneal and lack serosa (ie, the esophagus and rectum). 

The early integrity of the anastomosis is dependent on formation of a fibrin seal on the serosal side, which achieves watertightness, and on the suture-holding capacity of the intestinal wall, particularly the submucosal layer. There is a significant decrease in marginal strength during the first week due to an early and marked collagenolysis. The lysis of collagen is carried out by collagenase derived from neutrophils, macrophages, and intraluminal bacteria. Collagenase activity occurs early in the healing process, and during the first 3 to 5 days collagen breakdown far exceeds collagen synthesis. The integrity of the anastomosis represents equilibrium between collagen lysis, which occurs early, and collagen synthesis, which takes a few days to initiate. Collagen synthesis in the GI tract is carried out by both fibroblasts and smooth muscle cells.