CHAPTER ONE
INTRODUCTION
The gastrointestinal tract is the part of the digestive system that extends from the beginning of the oesophagus to the termination of the anal canal. It comprises a tubular oesophagus leading to a stomach which is secular, but shows both species and individual differences. Beyond the stomach, a tubular small intestine, consisting of a duopdenum and a jejunoileum, leads to a large intestine which terminates as the anal canal. All major subdivisions of the gastrointestinal tract (alimentary canal) are subject to carination in shape depending on the nature and volume of contents, but the range of variation under physiological conditions is most strongly marked in the stomach and large intestine, both of which characteristically exhibit more intermittent retention and evacuation of contents than other parts of the gut.
Gastrointestinal motility is the spontaneous rhythmic and alternate contractions and relaxations at a remarkably regular frequency of the gut caused by the inherent contractile elements of the visceral smooth muscles that line the walls of the gastrointestinal tract. The major part of the smooth muscle of the gastrointestinal tract is distributed in a thick circular layer and a much thinner longitudinal layer. The circular layer is responsible for most of the visible gastrointestinal movements.
In this project, isolated tissue preparation was used to examine the effect of cola nitida on the intestinal motility of Rabbits. W. Haffter, in 1854, first used this method to study small excised segments of bowel contracting in tiny bath of warm, oxygenated locke’s solution. The chemical composition of Locke’s solution is as follows: Nacl 0.9 percent; KCI o.042 percent; caClz 0.024 percent Na Hco3 0.015 percent; glucose 0.1 percent (Andrew, 1972). But Magnus (1904) popularized the method and showed its usefulness in pharmacological work and as a result, it is popularly known as Magnus method. The effect of cola nitida on Rabbits gastrointestinal tract was made possible as a small excised tissue segment from the Rabbit gut continues to undergo spontaneous rhythmic movements in vitro provided the isolated tissue is bathed in a physiological solution. This automaticity or inherent rhythmicity of the smooth muscle of the rabbit gastrointestinal tract may be due partly to the local nervous mechanism (myenteric plexus) and partly to the properties of the smooth muscle – pacemaker cells. The ‘pacemaker ‘cells responsible for the initiation of segmental contractions in the small bowel are located in the second part of the duodenum in the neighbourhood of the point of entruy of the nile and pancreatic ducts. Both neurogenic and myogenic functions are regulated through central nervous system reflexes by way of the autonomic nerves. Transmitter substances and some drugs that act by way of the receptor located on the smooth muscle cells mimic the effect of stimulation and affect gastrointestinal motility.
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