Defecation beginning of the large intestine peristalsis deliver feces into the rectum for expulsion. Feces go and stretch the ampulla of the rectum followed by relaxation of the internal anal sphincter. To avoid spontaneous stools, occurs reflex contraction of the external anal sphincter and pelvic floor muscle contractions are innervated by the pudendal nerve. The brain receives stimuli urge to defecate and the external anal sphincter was ordered for relaxation, thus removing the contents of the rectum with the help of the abdominal wall muscle contraction. This contraction will raise the pressure in the stomach, relaxation of the sphincter and the elevator ani muscle. Both sympathetic and parasympathetic innervation involved in the process of defecation.
The pathogenesis of constipation varies, multiple causes, including several overlapping factors. Although constipation is a lot of complaints in the elderly, colonic motility was not affected by age. Normal aging process does not result in a slowing of gastrointestinal trip. Pathophysiological changes that cause constipation is not due to age but is particularly marked in those with constipation.
Research with radio-opaque markers ingested by healthy elderly people who do not get a change of the total time of bowel movements, including motor activity of the colon. About the time of bowel movements by following the radiopaque markers are swallowed, normally less than 3 days already incurred. In contrast, studies in older people who suffer from constipation bowel movements indicate an extension of time of 4-9 days. In those treated or bedridden, can be extended to 14 days. Radioactive markers were used primarily slow the course of the left colon and no later than when the expenditure of the sigmoid colon.
Electrophysiological examination to measure motor activity of the colon of patients with constipation showed reduced motor responses of the sigmoid due to reduced intrinsic innervation because myentericus plexus degeneration. Found also reduced nerve stimulation in circular smooth muscle that can lead to an increased time of bowel movements. Individuals over the age of 60 years was also found to have plasma levels of beta-endorphins are increased, accompanied by an increase in endogenous opiate binding to receptors in the gut. This is evidenced by the effect of dosage opiate constipation which can cause relaxation of colonic tone, reduced motility, and inhibits gastric-colonic reflex.
In addition, there is a tendency of decrease in sphincter tone and strength of smooth muscle associated with age, particularly in women. Patients with constipation have a greater difficulty to remove the small, hard stools that attempts to push harder and longer. This can result in pressure on the pudendal nerve, causing further weakness.
