Swallowing is a highly complex set of events controlled by a swallowing centre in the medulla. A normal adult swallows between 100 and 600 times per day, one-third of these accompany eating and drinking and the remaining events occur when breathing out. Relatively few swallows occur during sleep (<10%). The primary stimulus for swallowing food is provided by sensory stimuli originating from receptors located within the sensory
Gastric Cardiac Gland
Figure 4.2 Transverse section through the cardia
Oesophageal - Cardiac Gland
Figure 4.2 Transverse section through the cardia fields of the mouth and pharynx. Non-prandial swallowing is driven by salivation and occurs without apparent cerebral participation
The resting pressure in the oesophagus reflects the changes due to breathing which cause cycles of positive and negative intrathoracic pressure between -5 to -10 mm Hg (Torr) during inspiration, to 0 to +5 mm Hg during expiration. On swallowing, the upper oesophageal sphincter relaxes for a period of about 1 second and then constricts. The swallow is associated with a transient decrease in pressure followed by a primary peristaltic wave of high pressure which travels towards the stomach at a speed of 2 to 6 cm s-1 in the proximal oesophagus, gradually becoming faster by the time it reaches the distal oesophagus (Figure 4.3). The lower oesophageal sphincter relaxes usually about 2 seconds after the initiation of swallowing for a period of 5 to 10 seconds allowing entry of the swallowed bolus.
The peak of the peristaltic wave is usually above 40 mm Hg, but there is considerable intra-subject variation. If a second swallow is taken before the peristaltic wave from the first swallow has reached the base of the oesophagus, then the initial peristaltic wave is
Upper Oesophageal Sphincter
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