A biopsy from the upper third of the esophagus shows the muscularis externa composed of which type of muscle?

• A Skeletal muscle only ✓
• B Smooth muscle only
• C Mixed smooth and skeletal muscle
• D Cardiac muscle

Explanation

The muscularis externa of the esophagus shows a characteristic transition along its length. The upper third is entirely skeletal muscle, the middle third is a mixture of skeletal and smooth muscle, and the lower third is entirely smooth muscle. This reflects voluntary initiation of swallowing proximally and involuntary peristalsis distally.

Reference: Wheater's Functional Histology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.