Aging of Digestive System
The esophagus is the muscular tube from the throat to the stomach. It has sphincters at each end that remain closed until food is swallowed. Peristalsis is the wavelike movement along the muscles of the gastrointestinal tract that moves food through the system.
Peristalsis begins in the esophagus and it effects the opening and closing of the sphincters. As a person ages, peristaltic contractions in the esophagus decrease and interfere with the passage of food into the stomach and the proper functioning of the sphincters. Other contractions of the muscle occur and they, too, interfere with the movement of food.
The mucous lining of the stomach-gastric mucosa-is normally thick with glands that secrete acid, mucin, and enzymes. With age, the gastric mucosa atrophies and secretions diminish. It is unclear whether or not movements of the stomach are affected by age.
Villi are minute, finger-like projections on the mucous membrane lining the small intestine. They number between four and five million, and each one contains a lymph channel and a network of capillaries. Around the villi are cells with microvilli. Digested food is absorbed into both. Because of the large number of these tiny projections, the surface area of the small intestine is about ten square miles. A decrease in cells and enzymes due to aging, therefore, does not greatly affect absorption in the small intestine. Peristalsis is decreased. In the colon, or large intestine, where the electrolytes and water are absorbed from the indigestible components of food, there is also some atrophy and reduced motility.
The liver gets smaller with age, decreasing the space it has to store blood, minerals, and vitamins. Liver functions of synthesizing bile and metabolizing carbohydrates, fats, and proteins are basically unaltered by age alone. Changes in enzymes reduce the liver`s ability to metabolize drugs.
The gallbladder, a pear-shaped sac under the liver, is a reservoir for the bile, which it expels into the small intestine when stimulated by the presence of gastric acid and fatty food. The incidence of gallstones, consisting mainly of cholesterol, protein, and the pigment bilirubin, does increase with advancing age. The formation of gallstones seems to be related to bile that is high in cholesterol.
Reference :
Farrell J : Nursing Care of the Older Person, J.B. Lippincott Company, Philadelphia, 1990.
