Disruption of one of these mechanisms can result in constipation. Defecation starting peristalsis of the large intestine to the rectum to deliver feces removed. Feces enter and stretch the ampulla of the rectum followed by relaxation of the internal anal sphincter. To avoid spontaneous spending stool, occurring reflex contraction of the external anal sphincter and pelvic floor muscle contraction that is innervated by the pudendal nerve. The brain receives stimuli desire for defecation and external anal sphincter relaxation was ordered to, so the rectum expel its contents with the help of muscle contractions of the abdominal wall. This contraction will raise the pressure in the stomach, and muscle relaxation of the sphincter ani elevators. Both sympathetic and parasympathetic innervation involved in the process of defecation.
The pathogenesis of constipation varied, 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 not due to age but is particularly the case for those with constipation.
Study with radiopaque sign 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 time 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 showed an extended time of 4-9 days. In those treated or bedridden, can be extended to 14 days. Radioactive markers used mainly slow the course of the left colon and the slowest time of 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 bowel movements.
Individuals over the age of 60 years are also shown 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 that 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 muscles 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.