Question

List and describe the physiological changes related to the digestive system of the elderly. Answered based on pathophysiological principles and specifically those related to aging.

Book link

• VanMeter, K.C., & Hubert, R.J. (2018). Gould's pathophysiology for the health professions. (6th ed.). St. Louis, MO: Elsevier Saunders. ISBN 9780323414425

Answer 1

The many functions of the digestive system are differently affected by age, making older people more prone to gastrointestinal conditions.

Ageing can have drastic effects on the functions of the digestive system. One of these is reduced appetite due to changes in hormone production and an alteration in smell and taste. Physiological changes in pharyngeal skills and oesophageal motility may lead to dysphagia and reflux. In the intestines, several factors contribute to changes in the regular gut microbial fauna, making older people more prone to bloating, pain and bacterial infection. There is also a drastic age-associated rise in the incidence of several gut pathologies including cancer of the colon.

The ‘anorexia of ageing’ :-

Food intake diminishes with age due to a range of complex reasons that lead to reduced appetite. These include physiological changes and changes in psychosocial and pharmacological circumstances.

Appetite is controlled mainly by sensors in the gastrointestinal tract, which detect the physical presence of food and prompt the GI tract to produce a range of hormones. These are released before, during and after eating, and control eating behaviours, including the amount consumed. They include:

• Ghrelin;
• Peptide tyrosine tyrosine (PYY);
• Cholecystokinin (CCK);
• Insulin;
• Leptin

The mouth:-

The lips, tongue, salivary glands and teeth all play a role in chewing, breaking down and swallowing food. Age-related shrinkage of the maxillary and mandibular bones and reduction in bone calcium content cause a slow erosion of the tooth sockets, leading to gum recession and an increased risk of root decay .

Swallowing:-

Having formed a bolus of food, the mouth prepares to swallow. The bolus reaches the posterior pharyngeal wall and the musculature contracts around it; swallowing occurs and food travels through the upper oesophageal sphincter into the oesophagus. With age, the muscular contractions that initiate swallowing slow down, increasing pharyngeal transit time.

The oesophagus:-

In general, the motor function of the GI tract is relatively well preserved in healthy older people, but there are significant changes in oropharyngeal and oesophageal motility. In the very old, impaired oesophageal motility is common; oesophageal peristalsis weakens with age.

The stomach :-

The stomach acts as a reservoir for food, allowing us to eat at regular intervals. With age, it cannot accommodate as much food, primarily because its wall loses elasticity.

The small intestine:-

The main function of the small intestine is to digest and absorb food. It produces a range of digestive enzymes, supported by the pancreas and liver.

Absorption of nutrients occurs in the jejunum and ileum, the second and third regions of the small intestine. The lining of the small intestine is shaped into microscopic folds (villi), which increase the surface area available for absorption. Although an age-related reduction in villus height has been shown, the impact on nutrient uptake does not seem to be clinically significant.

The large intestine:-

Peristalsis is affected by the age-related atrophy of the mucosa and muscle layers of the colon. The walls of the colon sag, prompting the formation of pouches (diverticuli). Straining to eliminate faeces may put additional pressure on weakened blood vessel walls, giving rise to haemorrhoids.

Gut microbes:-

The commensal microorganisms inhabiting the lumen of the colon are prevented from entering surrounding tissues by a single layer of epithelial cells that form an impermeable mucosal barrier. This barrier becomes ‘leaky’ with age . As the barrier function of the mucosal immune system is impaired, the incidence of GI pathogen infections is higher – and is a major cause of morbidity and mortality in older people.

The accessory organs :-

With age, the pancreas, which generates four major digestive enzymes, decreases in weight and some of its tissue undergoes fibrosis. Its exocrine function is impaired and the secretion of chymotrypsin and pancreatic lipase reduced.