HUMAN BIOLOGY

208 Chapter 11

Digestive system Disorders

“Heartburn” is an upper gi tract disorder

The main symptom of gastroesophageal reflux disease,

or GeRD, is often called “heartburn,” but it has nothing to

do with the heart. With this common disorder acidic chyme

backs up into the esophagus when the lower esophageal

sphincter doesn’t close properly. The irritation causes burn-

ing in the upper chest and throat. Mild cases often can be

controlled by over-the-counter drugs that reduce stomach

acid and by limiting intake of acidic foods such as toma-

toes, orange juice, coffee, and alcoholic beverages.

Hepatitis and cirrhosis strike the liver

Hepatitis is inflammation of the liver. Obesity, certain

drugs, and environmental toxins may trigger it. Some

types are caused by viruses that are transmitted in body

fluids such as blood and semen (see Chapter 16). The

inflammation may subside with treatment, although some

patients suffer major, irreversible damage for which the

only option is a liver transplant. Long-term inflamma-

tion due to heavy alcohol consumption causes alcoholic

cirrhosis (sir-oh-sis), in which damaged liver cells are

replaced by connective tissue “scars” (Figure 11.14).

Colon problems range from

constipation to cancer

It’s normal to “move the bowels,” or defecate, from three

times a day to once a week. In constipation, food residues

remain in the colon for too long, too much water is reab-

sorbed, and the feces become dry, hard, and difficult to

eliminate. Constipation is uncomfortable, and it is a com-

mon cause of the enlarged rectal blood vessels known as

hemorrhoids.

Constipation is often caused by a lack of bulk in the

diet. “Bulk” is the volume of fiber (mainly cellulose from

plant foods) and other undigested food material that is not

decreased by absorption in the colon. Much of it is insoluble

fiber such as cellulose and other plant compounds that

humans cannot digest (we lack the required enzymes) and

that does not easily dissolve in water. Wheat bran and the

edible skins of fruits are just two examples. (Plant carbohy-

drates such as fruit pectins that swell or dissolve in water

are soluble fiber.)

If you eat too little fiber, you are much more likely to be

in the 50 percent of the U.S. population in whom the colon

has formed diverticula—knoblike sacs where the inner colon

lining protrudes through the wall of the large intestine.

Inflammation of a diverticulum is called diverticulitis,

and it can have quite serious complications, including

peritonitis, if an inflamed diverticulum ruptures. Much

more common is diverticulosis (Figure 11.15), in which

diverticula are there but have not (yet) become inflamed.

Have you ever heard of someone having a “spastic

colon”? This problematical condition also is known as

iBS, or irritable bowel syndrome. IBS is the most com-

mon intestinal disorder. It often begins in early to mid

adulthood, and it affects twice as many women as men.

The direct trigger of IBS symptoms—abdominal pain and

alternating diarrhea and constipation—is a disturbance

in the smooth muscle contractions that move material

through the colon. New research implicates a prior bacte-

rial infection as the root cause in some cases. Reports that

consuming probiotics (“gut-friendly” bacteria such as Bifi-

dobacterium infantis) helps tame post-infectious IBS support

this hypothesis.

crohn’s disease is an inflammatory disorder that

affects various organs including the eyes, liver, skin,

and intestines. In some patients the intestinal lining is

so severely damaged that much of the intestine must be

removed (Figure 11.16). Although Crohn’s isn’t curable, new

treatment options are helping patients live with the disease

more comfortably than ever before.

Figure 11.15 Green areas in this X-ray are knoblike

diverticula.

Scott Camazine/Science Source

11.9

Figure 11.14 Long-term heavy alcohol use can cause cirrhosis

of the liver. a A healthy liver. B A cirrhotic liver, in which a great

deal of scarring has occurred. (A: Southern Illinois University/Science Source;

B: Martin M. Rotker/Science Source)

a B

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