Describe the physiology of gastric emptying (80% of marks). Outline the gastrointestinal effects of erythromycin (20% of marks).
This question was best answered by using a classification system, or systematic approach to
gastric emptying. Receptive relaxation (triggered by movement of food through the pharynx
and oesophagus), vagally mediated relaxation of fundus and upper body of stomach, the
pyloric pump (being intense peristalsis in lower body of the stomach that results in stomach
emptying) and the pyloric sphincter(a circular muscle that allows water and fluids to easily
pass through but restricts solids until it is mixed in chime to almost fluid consistency).
Candidates were also expected to mention regulatory factors e.g. food volume through
myenteric reflexes / gastrin stimulatory motor effects and enhanced pyloric pump, acidity
and osmolality of chyme in duodenum, presence of breakdown products of protein and fat
through enteric nervous system, sympathetic and parasympathetic nervous systems and
hormones such as cholecystokinin, secretin and gastric inhibitory peptide. Erythromycin is a
commonly used prokinetic and some knowledge of effects was expected (e.g. the fact that it
stimulates motilin receptors on GI smooth muscle and promote onset, frequency and
duration of migrating motor complex, from stomach and spreading caudally thus increasing