Diaphragmatic and oesophageal activity in regurgitation in sheep: an electromyographic study.

Abstract

SUMMARY1. Electromyographic (e.m.g.) recordings of reactions of the oesophagus, vertebral and costal fibres of the diaphragm and from the reticulum -one of the cranial divisions of the stomach were made during the regurgitation of rumination in sheep.2. E.m.g.s indicated that a contraction of the caudal thoracic oesophagus developed over a period of about 2 sec before, and ceased at the time of, the more forceful inspiratory effort associated with regurgitation.3. This contraction was confined to the caudal region of the thoracic oesophagus in which it was characteristically more prolonged and intense in its most caudal part within 15-25 mm of the hiatus oesophageus. It is interpreted to contribute to development or intensification of a caudal thoracic oesophageal sphincter.4. The more forceful inspiratory effort at the time of regurgitation was due to costal fibres of the diaphragm. Although active normally during inspiration the vertebral fibres of the hiatus oesophageus do not contribute to this more forceful inspiration. This may facilitate regurgitation of digest. Similarly, inactivity of vertebral but not postal fibres detected during primary oesophageal contractions (of swallowing) may make for easier passage of digesta into the stomach.

Oesophageal and diaphragmatic activity during sucking in lambs

“…The electrodes used, the technique of their insertion and longevity of recordings obtained with them have been referred to previously (Titchen, 1976(Titchen, , 1979Harding, Johnson, McClelland & Titchen, 1976;Newhook & Titchen, 1976). The radiographic apparatus used was a G.E.…”

“…In Melbourne, recordings were made with the apparatus described previously (Titchen, 1979): in Oxford, Neurolog (Digitimer Ltd., U.K.) amplifiers were used in conjunction with a Medelec (U.K.) fibre-optic recording oscilloscope or Brush (U.S.A.) or Beckman (U.S.A.) chart recorders. The two lambs studied in Oxford had latex balloons, 15 x 4-5 mm introduced via an intercostal approach into the thorax where they were retained in a position immediately beneath the thoracic wall.…”

“…This reaction has been described in adult sheep in which vertebral fibres may no longer participate in respiratory movements during primary contractions of the oesophagus, at the time of regurgitation of rumination and in response to distension ofthe thoracic oesophagus (Titchen, 1979(Titchen, , 1980. The movement of ingested material from the pharynx into the oesophagus involves reactions which serve to ensure that the swallowed material does not enter the respiratory tract.…”

Responses of upper airway, intercostal and diaphragm muscle activity to stimulation of oesophageal afferents in dogs.

“…in the gastrointestinal tract) can have strong effects on respiratory activity. For example, distension of the oesophagus N. S. CHERNIACK AND OTHERS produces a powerful inhibition of the crural part of the diaphragm (Duron, 1975;Titchen, 1979). Also, stimulation of afferent endings in the abdominal viscera leads to inhibition of phrenic activity (Prabhakar, 1983).…”

Retrograde Oesophageal Contractions in the Dog

“…It is well accepted that the mammalian oesophagus contracts during swallowing, but little emphasis has been given to the possibility that oesophageal contractions may contribute to the return of material from the stomach to the mouth, except in ruminants, where retrograde oesophageal contractions accompany the regurgitations of rumination and contribute to eructation (Stevens & Sellers, 1960;Hill, 1965;Titchen, 1979;Carr, Scott & Titchen, 1983;Heywood & Wood, 1985a).…”