Age-Related Changes in the Gastrointestinal System
The two major changes that occur in the gastroin-testinal tract with aging are the reduction in the proliferation rate of epithelial cells and the loss of neurons from the walls.
Studies have shown that most changes in the oral cav-ity in elderly individuals are a result of pathology and not normal aging. There may be shrinkage and fibro-sis of the root pulp, and the gums may be retracted. Some loss of bone density may occur in the jaws. The major change that occurs is the loss of teeth, with re-sultant impairment of chewing. Salivary flow may be reduced as a result of the reduced sensation of smell and taste and the loss of secretory tissue.
The function of the esophagus is essentially pre-served. The motor activity of the esophagus may be uncoordinated, with delayed entry of food into the stomach and a feeling of substernal fullness.
There is atrophy of the stomach mucosa, with dimin-ished capacity to secrete hydrochloric acid. The motility of the stomach may be reduced, with slower emptying.
The villi in the mucosa are atrophied to some extent, becoming broader and shorter with resultant decrease in surface area for absorption. The volume of gastric se-cretion is decreased with age. There is no evidence that absorption of major nutrients is impaired; however, the effect on the function is still not determined fully.
The motility of the colon may be decreased, with some reduction in blood flow. The bowel habits are not significantly affected. It is believed that more dis-tention of the colon is required for discomfort to be felt and this may be one reason for the constipation that is common in elderly persons. Atrophy of mus-cle, loss of neurons, and changes in collagen are other factors that affect colon motility of the.
The pancreas undergoes some changes with age. The ducts are dilated and deposits of calcium and other pigments occur. Fat intolerance in the older age group is sometimes attributed to a decrease in lipase production. However, this seems unlikely because the pancreas has a large functional reserve and the ca-pacity to increase its secretion ten times more than that required to digest normal levels of fat in the diet.
The liver diminishes in size, with destruction of hepa-tocytes. Fibrous tissue replaces the dead cells. The var-ious enzymes and protein synthesis are diminished. The capacity to metabolize drugs also reduces with age.