The primary difference between the upper and lower esophagus lies in the type of muscle tissue that comprises them.
Muscle Composition
The esophagus, unlike most other organs, contains both skeletal and smooth muscle. Its composition varies along its length:
- Upper Esophagus (approximately 2-4 cm): This section is composed entirely of skeletal muscle. This allows for voluntary control during the initial stages of swallowing.
- Middle Esophagus: This section contains a mixture of skeletal and smooth muscle. This transitioning zone reflects the shift from voluntary to involuntary control.
- Lower Esophagus (approximately 11 cm): This section is made up entirely of smooth muscle. This part of the esophagus functions under involuntary control, propelling food into the stomach.
In summary, the upper esophagus contains skeletal muscle, allowing for voluntary control of swallowing, while the lower esophagus consists of smooth muscle, responsible for involuntary peristalsis to move food into the stomach. The middle esophagus is a transition zone containing both types of muscle.
