
Esophagus: Muscularis externa
Muscularis externa is formed of inner circular and outer longitudinal layers. In the upper third of the esophagus, these layers are formed of skeletal muscle, which is involved with swallowing, a voluntary action. In the middle one-third (seen here), skeletal and smooth muscles are intermixed. In the lower one-third, only smooth muscle is present. Innervation is provided by Auerbach’s plexus. 400x

Submucosa
Muscularis externa is formed of inner circular and outer longitudinal layers. In the upper third of the esophagus, these layers are formed of skeletal muscle, which is involved with swallowing, a voluntary action. In the middle one-third (seen here), skeletal and smooth muscles are intermixed. In the lower one-third, only smooth muscle is present. Innervation is provided by Auerbach’s plexus. 400x

Muscularis externa
Muscularis externa is formed of inner circular and outer longitudinal layers. In the upper third of the esophagus, these layers are formed of skeletal muscle, which is involved with swallowing, a voluntary action. In the middle one-third (seen here), skeletal and smooth muscles are intermixed. In the lower one-third, only smooth muscle is present. Innervation is provided by Auerbach’s plexus. 400x

- Smooth muscle longitudinal section
Muscularis externa is formed of inner circular and outer longitudinal layers. In the upper third of the esophagus, these layers are formed of skeletal muscle, which is involved with swallowing, a voluntary action. In the middle one-third (seen here), skeletal and smooth muscles are intermixed. In the lower one-third, only smooth muscle is present. Innervation is provided by Auerbach’s plexus. 400x

- Skeletal muscle longitudinal section
Muscularis externa is formed of inner circular and outer longitudinal layers. In the upper third of the esophagus, these layers are formed of skeletal muscle, which is involved with swallowing, a voluntary action. In the middle one-third (seen here), skeletal and smooth muscles are intermixed. In the lower one-third, only smooth muscle is present. Innervation is provided by Auerbach’s plexus. 400x

- Smooth muscle cross section
Muscularis externa is formed of inner circular and outer longitudinal layers. In the upper third of the esophagus, these layers are formed of skeletal muscle, which is involved with swallowing, a voluntary action. In the middle one-third (seen here), skeletal and smooth muscles are intermixed. In the lower one-third, only smooth muscle is present. Innervation is provided by Auerbach’s plexus. 400x

- Skeletal muscle cross section
Muscularis externa is formed of inner circular and outer longitudinal layers. In the upper third of the esophagus, these layers are formed of skeletal muscle, which is involved with swallowing, a voluntary action. In the middle one-third (seen here), skeletal and smooth muscles are intermixed. In the lower one-third, only smooth muscle is present. Innervation is provided by Auerbach’s plexus. 400x

- Auerbach’s plexus
Muscularis externa is formed of inner circular and outer longitudinal layers. In the upper third of the esophagus, these layers are formed of skeletal muscle, which is involved with swallowing, a voluntary action. In the middle one-third (seen here), skeletal and smooth muscles are intermixed. In the lower one-third, only smooth muscle is present. Innervation is provided by Auerbach’s plexus. 400x