Abstract:
Solid-state esophageal manometry was used to study physiology of the normal
llama esophagus. Esophageal baseline pressures, esophageal response to water
swallows and to balloon distention, and other motor activity of the esophagus
during experiments were measured throughout the entire length of the esophagus.
Gross and histologic anatomy, muscle fiber type classification, and ultrastructural
morphology were used to study anatomy of the normal llama esophagus. The
methods as described were also applied to study the physiology and anatomy of
two llamas with megaesophagus and one llama with esophageal motor
abnormalities.
Primary peristalsis in response to a water swallow is unique in the llama
esophagus. Duration of contraction is very short. Propagation velocity of the
peristaltic wave is fast, approximately ten times of that of the human. Amplitude of
contraction and mean rate of pressure change per unit time are the greatest in the
pharyngoesophageal region and the lowest in the lower esophageal sphincter
region. Length of the cervical portion of the esophagus is almost twice that of the
thoracic portion in keeping with long neck. Submucosal glands are abundant
throughout the esophagus. Type 2 muscle fibers are predominant throughout the
esophagus. Type 1 muscle fibers are also present and gradually increase in the
distal portion of the esophagus. Generally, ultrastructure of the striated muscle of
the esophagus is similar to that of the skeletal muscle.
Primary peristalsis was abnormal in llamas with megaesophagus. More than a
half of the distal esophagus was aperistaltic. Manometric findings corresponded to
anatomical findings. Esophageal dilation was remarkable in the distal portion of the
esophagus. Evidence of denervation atrophy of the esophageal striated muscle was
not found in the cranial cervical region, but was found in the middle cervical region
through the distal thoracic region.
This study provides extensive normal data on the llama esophagus to serve as a
baseline for further study of esophageal pathology in the llama. Findings from this
study suggest that denervating disease is a cause of megaesophagus in the llama,
although the exact nature of this disease is still unknown.
