Encyclopedia of Health and Medicine

10 The Gastrointestinal System
aging, gastrointestinal changes that occur with
The organs and structures of the gastrointestinal
system undergo numerous changes as an individual
grows older. At birth, the infant’s MOUTH supports
sucking and swallowing liquid nourishment.
With the eruption of TEETH and the elongation of
the head, developmental changes that occur in
early childhood, the oral cavity shifts to support
chewing and swallowing solid foods. By three
years of age most children in the United States are
eating fully solid foods, their gastrointestinal systems
capable of digesting nearly any food an
adult’s body can accommodate.
The gastrointestinal system remains fairly stable
until about the fourth decade of life, at which time
changes in muscle tone, vasculature (blood vessel
function and blood supply), and body composition
begin to affect its structures and functions. Some
of these changes are physiologic and others relate
to lifestyle; combined they result in increased gastrointestinal
problems such as GASTROESOPHAGEAL
REFLUX DISORDER (GERD), GALLBLADDER DISEASE, DIA-
BETES (altered functioning of the PANCREAS), and
PEPTIC ULCER DISEASE. Changes such as weight gain
or OBESITY may affect digestive functions as well,
particularly with ABDOMINAL ADIPOSITY, a pattern
of body fat distribution in which excess body
fat accumulates in the abdomen. This accumulation
can compress the intestines, slowing intestinal
motility. In the fifth decade of life and
beyond, there is increased risk for STOMACH CANCER,
LIVER CANCER, PANCREATIC CANCER, and COLORECTAL
CANCER.
Changes in vasculature, which often result
from other health circumstances such as HYPERTEN-
SION (high BLOOD PRESSURE) and ATHEROSCLEROSIS,
affect gastrointestinal motility and absorption. A
person age 50 absorbs about a third less calcium
than a person age 25. Absorption of other vital
nutrients slows as well; many older adults benefit
from NUTRITIONAL SUPPLEMENTS. In the seventh
decade of life and beyond, the SALIVARY GLANDS and
digestive glands slow production of their respective
secretions. Reduced saliva makes chewing
and swallowing more difficult; reduced gastric
juices further impede digestion and absorption.
These changes increase the potential for gastrointestinal
disturbances such as DIARRHEA and CONSTI-
PATION.
Measures to preserve gastrointestinal health
can mitigate many of the age-related changes that
occur in the gastrointestinal system. These include
• eating a high-fiber, low-fat diet
• drinking six to eight ounces of water every
hour or two during waking hours
• maintaining healthy weight
• getting daily physical exercise
• having regular screening, such as COLONOSCOPY,
for colorectal cancer
• managing other health conditions such as diabetes
See also GENERATIONAL HEALTH-CARE PERSPECTIVES;
HYDRATION; MINERALS AND HEALTH; NUTRITIONAL NEEDS;
SIALOADENITIS; SIALORRHEA; VITAMINS AND HEALTH.
anal atresia A CONGENITAL ANOMALY, also called
imperforate ANUS, in which the anal opening that
allows the elimination of feces is missing or misplaced.
Diagnosis typically takes place within 24 to
48 hours following birth, with the passage of, or
failure to have, the first BOWEL MOVEMENT. Complete
anal atresia requires immediate surgery to
create a means for the body to pass stool; often
the surgeon creates a temporary COLOSTOMY (opening
from the large intestine through the abdominal
wall) until the infant can undergo any
necessary reconstructive surgery. When partial
anal atresia is present, the anus may open into
another structure such as the VAGINA or URETHRA.
Partial anal atresia also requires surgical repair.
After surgical reconstruction of the anus many
infants have normal bowel function. However
some infants have damage to, or are missing, the
nerves that regulate the anal sphincter, with
resulting FECAL INCONTINENCE. Anal atresia often
occurs in combination with other congenital
anomalies, notably NEURAL TUBE DEFECTS.
See also BOWEL ATRESIA; CONGENITAL HEART DIS-
EASE; ESOPHAGEAL ATRESIA; RECTAL FISTULA.
anal fissure Small tears in the tissue around the
ANUS. Anal fissures can be internal or external. They
typically are painful and may bleed with bowel
movements, resulting in small amounts of bright
red BLOOD on the toilet tissue or in the toilet bowl.