Neck position affects the dimensions of the rat cervical esophagus

Might esophageal structure allow dimensional alterations? The rat esophagus has elastic fibers, skeletal muscle and keratinized epithelium. Will they shorten as the neck flexes and lengthen as it hyperextends? In eight adult female rats under pentobarbital six dots of dye were placed rostrocaudally on the cervical esophagus. When prone on a flat surface the neck was flexed to about 6° short of perpendicular (84° ± 4° s.d.) and maintained by a head clamp. Greater flexion caused the chin to mask the most rostral dot. Interdot measurements were made using a dividers and digital micrometer. A 1 cm diameter vial was then placed under the shoulders. The measurements were repeated with the neck hyperextended to about 6° below 180°. Paired “t”‐tests compared distances between adjacent dots. The paired measurements (mm) were: 1.71 ± 0.26 vs 2.58 ± 0.40; 1.69 ± 0.21 vs 2.48 ± 0.29; 2.69 ± 0.40 vs 3.71 ± 0.61; 1.99 ± 0.26 vs 2.43 ± 0.23; 1.95 ± 0.25 vs 2.34 ± 0.31. As it lengthened the esophagus narrowed. At the level of the rostralmost and caudalmost dots its widths were 2.91 ± 0.28 vs 2.67 ± 0.23 and 2.76 ± 0.19 vs 2.21 ± 0.16. All differences but the rostralmost width were significant (P < 0.001). The cervical esophagus changes length and width as the neck moves. This is also likely in man. On looking down at one's plate while eating, esophageal dimensions and motility might differ from when one swallows while looking up at the waiter.