Final answer:
Cigarette smoking is a factor that contributes to lower esophageal sphincter incompetence, which can lead to heartburn and GERD. Smoking weakens the sphincter, and quitting smoking can improve its function.
Step-by-step explanation:
An example of a factor that contributes to lower esophageal sphincter incompetence, is D) Cigarette smoking. This is because smoking tends to weaken the lower esophageal sphincter, leading to problems like heartburn and potentially chronic conditions such as gastroesophageal reflux disease (GERD). The lower esophageal sphincter normally remains closed to prevent stomach contents from entering the esophagus, and its failure to stay closed can lead to damage to the mucous membrane of the esophagus due to the highly acidic stomach contents.
During pregnancy, hormones can cause the lower esophageal sphincter to relax, which often results in increased instances of heartburn and indigestion for pregnant women. Quitting smoking may help control reflux symptoms and maintaining a healthy weight can also bring improvement to those who are overweight and suffering from GERD. Unlike factors that open the sphincter in response to certain physiological conditions, cigarette smoking is a behavioral factor that can be modified to improve sphincter function.