10.12: Pancreas

The pancreas is a large gland in the space below the stomach and above the first section of the small intestine (Figure 10.1, Figure 10.9). Most of the pancreas consists of clusters of cells (exocrine cells) that secrete pancreatic juice into ducts within the pancreas. The ducts merge to form larger ducts, which finally converge and form one large pancreatic duct. This duct joins the common bile duct just before it enters the small intestine (Figure 10.8, Figure 10.9). Therefore, bile and pancreatic juice enter the small intestine through the same opening.

Figure 10.9 Pancreas. (Sources of images and videos below. Used with permission.)

Pancreatic juice contains several enzymes that hasten the chemical breakdown of large nutrient molecules. It also contains sodium bicarbonate, which neutralizes stomach acid and prevents it from injuring the small intestine. This process also helps provide a proper acid/base balance for the action of enzymes in the pancreatic juice and in small intestine secretions. The secretion of pancreatic juice is adjusted by the autonomic nervous system and by hormones from the small intestine.

Small clusters of cells (endocrine cells) that secrete hormones into the blood are widely scattered among the exocrine cells (Figure 10.9). These clusters are called islets of Langerhans. The endocrine cells are of two types: One type (alpha cells) secretes glucagon, and the other type (beta cells) secretes insulin. These hormones help maintain proper and fairly stable levels of glucose in the blood and affect the production and breakdown of proteins and lipids by body cells.

Age Changes

The slight age changes that occur in most components of the pancreas and its ducts do not have a significant effect on the amount of pancreatic juice produced. There may be a slight decrease in the production of certain enzymes (e.g., those for lipid digestion), sodium bicarbonate, and insulin. None of these changes are great enough to alter the ability of pancreatic secretions to digest nutrients, neutralize stomach acids, and regulate blood glucose levels. A main reason for the maintenance of pancreatic digestive function throughout life is the large reserve capacity of the pancreas. As little as 10 percent of the young adult pancreas is needed to produce enough pancreatic juice for normal digestion. Though the effectiveness of the pancreas is virtually unchanged by aging, hormone production is often significantly altered by other factors as people get older (e.g., obesity, lack of exercise) (Chapter 14).

Abnormal Changes

Pancreatitis

One of the more common abnormalities of the pancreas among the elderly is pancreatitis, or inflammation of the pancreas. Cases that develop quickly are called acute pancreatitis, and cases that develop over a prolonged period are referred to as chronic pancreatitis. Repeated or prolonged cases of acute pancreatitis lead to chronic pancreatitis.

Acute pancreatitis is usually caused by traumatic injury to the abdominal region (such as when the abdomen strikes the steering wheel in an automobile accident), consumption of alcoholic beverages (especially binge drinking), or blockage of the pancreatic duct by a gallstone. Chronic pancreatitis is usually caused by chronic alcohol consumption or blockage of the pancreatic duct by a gallstone.

In addition to causing extreme pain, acute pancreatitis may quickly become life-threatening. Vomiting can severely deplete the body of fluids and minerals, leading to circulatory, nervous, and muscle malfunctions. Bleeding or leaking of pancreatic enzymes into the blood or abdominal cavity can cause blood pressure to drop dramatically, resulting in circulatory failure. Pancreatic enzymes in the abdominal cavity can begin to digest nearby organs, causing destruction and perforation of those organs. Long-lasting muscle spasms may occur as blood calcium levels drop. Blood sugar levels may also drop as injured endocrine cells release insulin. Since the endocrine cells may be permanently damaged, individuals who survive these immediate dangers may be left with diabetes mellitus. Any case of acute pancreatitis can develop into chronic pancreatitis.

Three main problems develop in patients with chronic pancreatitis: recurrent pain; poor protein and fat digestion caused by inadequate production of digestive enzymes; and inadequate regulation of blood sugar and diabetes mellitus resulting from reduced production of hormones.

Since excessive or chronic consumption of alcoholic beverages is a main cause of pancreatitis, many cases can be prevented by avoiding such drinking behaviors. Many other cases can be prevented by removing gallstones before they block the pancreatic duct.

Treatments for acute pancreatitis primarily involve preventing or reducing its effects and complications. Surgical procedures may be required to repair or remove injured organs or remove gallstones. Abstinence from alcoholic beverages is often necessary.

Pain from chronic pancreatitis is relieved with analgesics, and enzyme insufficiency is rectified by ingesting enzyme supplements with meals. Mild cases of diabetes mellitus can be managed by regulating diet and exercise; more severe cases may require the administration of insulin. As with acute pancreatitis, surgery may be necessary, and abstinence from alcoholic beverages is often required.

Cancer

Like all cancers, pancreatic cancer involves uncontrolled reproduction of cells. Almost all cases involve cancer of the exocrine cells. Cancer of the pancreas is the fifth leading cause of death from cancer, and it accounts for 3 percent of all cancers and 5 percent of all deaths from cancer. Within the digestive system, only cancer of the large intestine occurs more frequently. The incidence of pancreatic cancer rises with age, and the incidence is highest among men over age 75. Several risk factors for pancreatic cancer have been identified; smoking cigarettes, eating a diet high in animal fat, eating many foods containing high amounts of nitrates and nitrites as preservatives (e.g., bacon, cold cuts), consuming much coffee, and having diabetes mellitus.

Cancer of the pancreas is especially dangerous because it is usually detected only after it has become quite advanced. Indications include being jaundiced, losing weight, having abdominal or back pain, and having symptoms of diabetes mellitus such as unusually high thirst, hunger, and excessive urine production. This cancer causes pancreatic failure, which includes poor digestion of proteins and fat, and diabetes mellitus. Pancreatic cancer often spreads through the hepatic portal system to the liver, where it causes liver failure.

The chances of developing pancreatic cancer may be lowered by avoiding smoking and other dietary risk factors. Avoiding risk factors for diabetes mellitus, such as being obese and being sedentary, may also help.

Though surgery, chemotherapy, and radiation therapy have been employed as treatments for pancreatic cancer, no effective treatment for this disease is known. Pancreatic cancer is usually fatal within 1 year of the diagnosis.