Feline Esophagus Research Articles

Movement of the feline esophagus associated with respiration and peristalsis. An evaluation using tantalum markers.

The outer, lateral esophageal walls in the distal half of the esophagus in each of five cats were labeled with small tantalum wires. About 8 wk later, esophageal motion associated with respiration and peristalsis, induced by injecting barium boli (5 ml each) into the proximal esophagus, was recorded on cine and serial biplane roentgenograms while recording intraluminal esophageal pressures simultaneously by manometry. Esophageal motion was also evaluated without a manometric tube in place. The coordinates for each marker were digitized and a computer was used to plot marker position against time. During respiration, the markers passively made a shallow, 2-10 mm excursion on the longitudinal esophageal axis. This movement was synchronous with thoracic and diaphragmatic movement and changes in intraluminal esophageal pressure. Immediately after the onset of peristalsis, the markers made a pronounced oral movement of 10 mm or more above their mean respiratory position, as if to engulf the bolus. Markers in opposing esophageal walls approximated one another and commenced an aboral movement as the bolus tail, which was essentially co-incident with onset of the manometric pressure complex, passed the marker sites. The markers returned to their respective rest positions essentially coincident with passage of the pressure complex peak and then moved below their respective rest positions. The aboral excursion occurred predominantly after the bolus had emptied into the stomach. The magnitude and duration of oral excursion was significantly greater for the distal than for the more proximal markers; conversely, the magnitude and duration of aboral excursion was greater for the proximal than for the more distal markers. During the peristaltic sequence, the labeled portion of the esophagus shortened from 26 to 46% of its resting length. No evidence of esophageal torque was shown. These findings suggest that both the longitudinal and circular esophageal musculature play an active and important role during peristaltic transport of a bolus through the esophagus.

Electric and motor activity of innervated and vagally denervated feline esophagus.

Motor and electric activities of the feline esophagus were detected before and after vagotomy by use of intraluminal pressure detectors and chronically implanted platinum electrodes. These were placed in the midesophagus (E1), at the three-quarter point (E2) and in the lower 2 cm (E3). Both inner and outer layers of muscle were skeletal at E1 and smooth at E3, whereas at E2 the outer layer was predominantly skeletal and the inner predominantly smooth. Before vagotomy, contractions of the skeletal muscle fibers of the midesophagus were associated with pressure changes and action potentials of lesser amplitude, briefer duration and faster propagation than those of the smooth muscle fibers of the lower esophagus. The frequency of the skeletal muscle action potentials was greater than 25 cycles per second (cps), and that of the smooth muscle action potentials was less than 25 cps. The first recorded event during peristalsis was orad movement of the electrodes due to contraction of longitudinal fibers. After vagotomy, action potentials occurred with nearly every stimulation, but the incidence of intraluminal pressure increases was reduced. Repetitive responses were common. Action potentials with frequencies faster than 25 cps were eliminated in the lower quarter of the esophagus were orad movement of electrodes was also abolished owing to paralysis of longitudinal muscle fibers. The incidence of peristalsis was reduced during the first month after vagotomy to between 33 and 44% of responses, but thereafter its occurrence improved to 40 to 80% of responses. The predominant electromotor features of the period after vagotomy were persistent weakness, incoordination and repetitive responses in the lower esophagus, which prevented normal emptying of the organ.

Regional Distribution of Feline Esophageal Blood Flow

The regional distribution of esophageal blood flow has not been studied in man or in an animal whose esophageal musculature is histologically similar. The cat is the only common laboratory animal whose esophagus, like man’s, contains both striated and smooth muscle in the muscularis externa. Nutrient blood flow to sequential mucosal and muscular segments of the feline esophagus was determined by use of the indicator fractionation technique and cardiac output studies. The smooth muscle of the muscularis externa received a slightly higher flow (21 ml per min per 100 g) than did striated muscle (17 ml per min per 100 g). This relative similarity of nutrient flow to these histologically different muscle types may reflect that they function in concert in the esophagus and are under similar neural control. Blood flow to 1 gram of esophageal mucosa and muscularis externa was similar. This distribution differs from that reported for the stomach and small bowel where 1 gram of mucosa receives a greater nutrient flow than does the muscularis externa. These distribution differences reflect functional and morphological differences between these parts of the gastrointestinal tract.

The effect of denervation on feline esophageal function and morphology

Denervation of the feline esophagus leads to a severe motility disorder which is different from that recorded after denervation of the dog and monkey esophagus. Bilateral cervical vagotomy resulted in complete paralysis of the body of the esophagus, but peristalsis returned to that portion composed of smooth muscle. Esophageal dilatation occurred, and the incidences of relaxation and contraction of the inferior sphincter in response to swallowing were markedly reduced. These sphincteric abnormalities returned to normal after 6 months, but those in the body of the esophagus were unchanged for periods of 9 months. Esophageal dilatation occurred after vagotomy in all cats. Esophagomyotomy did not prevent this. Periesophageal vagotomy had a very inconstant effect. Sympathectomy had little effect on esophageal motility but caused marked diminution in the resting pressure of the inferior sphincter. When combined with vagotomy, sympathectomy prevented the effect of vagotomy on the sphincter but not on the body of the esophagus. None of these procedures induced a loss of ganglion cells in Auerbach's plexus.

Regional Distribution of Feline Esophageal Blood Flow

The regional distribution of esophageal blood flow has not been studied in man or in an animal whose esophageal musculature is histologically similar. The cat is the only common laboratory animal whose esophagus, like man’s, contains both striated and smooth muscle in the muscularis externa. Nutrient blood flow to sequential mucosal and muscular segments of the feline esophagus was determined by use of the indicator fractionation technique and cardiac output studies. The smooth muscle of the muscularis externa received a slightly higher flow (21 ml per min per 100 g) than did striated muscle (17 ml per min per 100 g). This relative similarity of nutrient flow to these histologically different muscle types may reflect that they function in concert in the esophagus and are under similar neural control. Blood flow to 1 gram of esophageal mucosa and muscularis externa was similar. This distribution differs from that reported for the stomach and small bowel where 1 gram of mucosa receives a greater nutrient flow than does the muscularis externa. These distribution differences reflect functional and morphological differences between these parts of the gastrointestinal tract.

Anatomy of feline esophagus with special reference to its muscular wall and phrenoesophageal membrane

The muscular wall of the esophagus and the hiatal anatomy of 13 cats were studied, with special reference to the amount of smooth muscle present and the phrenoesophageal membrane attachments. The lower esophageal wall of the cat has more smooth muscle than that of the dog, but less than that of the human. The distribution of myenteric plexi was more symmetric in the cat than in the dog or the human. The phrenoesophageal membrane of the cat differed from that of the dog or the human in that its descending limb was attached below the esophagogastric angle and its esophageal attachments were superficial.