CHAPTER 27
DISTURBANCES OF INTESTINAL
FUNCTION
Physiology and Pathophysiology
The complicated pattern of normal intestinal activity depends on pendular, circular and
segmental movements of the various sections of the intestinal tract to establish mixing of
the food with the gastric and intestinal secretion and to accomplish its digestion and
absorption. There is a wide range in the speed of intestinal activity, which is highest in
duodenum and jejunum, gradually slowing down towards the ileum, which is stimulated
reflexly (gastro-ileal reflex of Hurst) to move its semi-fluid contents into the caecum,
gradually filling the ascending and transverse colon. There, the absorption of salts and
water takes place by the slow function of the haustra, until at certain long intervals, by a
powerful mass movement of the transverse colon, the contents are transferred into the
descending and pelvic colon. While all these processes take place without conscious
awareness, the act of defaecation is initiated by conscious appreciation of an urge to
defaecate ('the call to stool'), which is caused by afferent impulses to the sacral spinal
centre and cerebral stations as a result of the filling and distension of sigmoid colon and
upper rectum. Efferent impulses emanating from the sacral centre set up an opening
mechanism, by evoking contractions of sigmoid and rectum and in turn relaxation of
the rectal sphincters to allow the passage of faeces, which is assisted by straining—i.e.
raising the abdominal pressure. Following emptying of the anal canal, a closing mechanism
comes into action by contracting the levator ani to restore the everted mucosa, while
contraction of the anal sphincter and relaxation of the tone of the colon takes place.
There are considerable variations of bowel habit amongst able-bodied individuals.
Connell
el al.
(1963) found, in a statistic study on an industrial community, only i per
cent of the population with bowel habits outside the range of three bowel actions per
week, to three per day, while in 88-5 per cent the frequency ranged from 5 to 14 bowel
actions per week. It is, therefore, essential for those concerned with the management of
the spinal paralysed to consider the pre-paraplegic habit of these patients when analysing
the intestinal abnormalities, especially in the stage of reconditioning.
Intestinal activity depends on a co-ordinated action of the various stations of the
nervous system. The influence of the cerebral mechanisms on gastrointestinal activity
is well known. Visual and olfactory impulses at the sight, smell or thought of food stimu
late active flow of gastric juice and accelerate the digestive process, while disagreeable
emotional states, such as fear, anger, worry, may result in complete depression of gastro
intestinal activity. The act of defaecation also depends on cerebral influences, which,
according to circumstances, may promote or inhibit the activity of the sacral spinal
centre. In inconvenient circumstances, the inhibitory influence of the cortex will cause
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