Which of the following statements regarding the muscularis externa of the esophagus is true?
A) The upper third portion of the esophagus consists of smooth muscle, the middle third portion is a mixture of smooth and skeletal muscles, and the lower third consists of skeletal muscle.
B) The entire muscularis of the esophagus consists of skeletal muscle only.
C) The entire muscularis of the esophagus consists of smooth muscle only.
D) The upper third portion of the esophagus consists of smooth muscle, and the remaining portion is a mixture of skeletal and smooth muscles.
E) The upper third portion of the esophagus consists of skeletal muscle, the middle third portion is a mixture of skeletal and smooth muscles, and the lower third consists of smooth muscle.

Question

Quizplus · Accepted Answer

The muscularis externa of the esophagus is unique in its composition: the upper third consists of skeletal muscle, allowing for voluntary control of swallowing; the middle third is a mixture of skeletal and smooth muscles, representing a transition zone; and the lower third consists entirely of smooth muscle, facilitating involuntary control of food passage into the stomach.

Which of the Following Statements Regarding the Muscularis Externa of the Esophagus