The esophagus has both skeletal (striated) and smooth muscle, arranged in two main layers. The upper part is mostly skeletal muscle, the lower part is smooth muscle, and the middle is a mix of both types.
Muscle types by region
- Upper third: composed mainly of skeletal (striated, voluntary) muscle, continuous with the muscles of the pharynx.
- Middle third: contains a mixture of skeletal and smooth (involuntary) muscle fibers.
- Lower third: composed entirely of smooth (involuntary) muscle, including the lower esophageal sphincter.
Muscle layer arrangement
- Inner layer: circular muscle fibers that encircle the esophagus and generate peristaltic waves to push food downward.
- Outer layer: longitudinal muscle fibers that run along the length of the esophagus and help shorten and widen the tube during swallowing.
