Question

which action allows the bolus to move from the esophagus into the stomach and prevents chyme from entering the esophagus?
a.) peristalsis
b.) upper esophageal sphincter relaxation
c.) mucus secretion
d.) lower esophageal sphincter relaxation

Explanation:

• Peristalsis (a): It is the wave - like muscle contraction that moves food (bolus) along the digestive tract. But it is a general movement mechanism and not specifically related to the sphincter - controlled movement between the esophagus and stomach.
• Upper esophageal sphincter relaxation (b): This sphincter is located at the top of the esophagus (near the pharynx) and is involved in allowing food to enter the esophagus from the pharynx, not in the esophagus - stomach junction.
• Mucus secretion (c): Mucus in the digestive tract mainly serves to lubricate and protect the digestive tract lining. It has no role in regulating the movement between the esophagus and stomach.
• Lower esophageal sphincter relaxation (d): The lower esophageal sphincter (LES) is located at the bottom of the esophagus (junction with the stomach). When it relaxes, the bolus can pass from the esophagus into the stomach. When it contracts, it prevents the acidic chyme (partially digested food in the stomach) from refluxing back into the esophagus.

Answer:

d. Lower esophageal sphincter relaxation