Digestive system

LadyofHats / Public domain

The body’s food processing complex supplies essential nutrients that fuel other organs and body systems. The digestive system’s two major components include the:
• GI tract
• accessory glands and organs.

GI tract
Beginning in the mouth and ending at the anus, the GI tract includes the:
• mouth — where chewing and salivation occur to make food soft and easy to swallow
• esophagus — where food enters by peristaltic waves that are activated by the glossopharyngeal nerves
• stomach — where digestion occurs in two phases:
–the cephalic phase
–the gastric phase
• small intestine — where digestion takes place in three major sections:
–the duodenum
–the jejunum
–the ileum
• large intestine — where absorption takes place and mostly indigestible material passes through the transverse colon, and then down through the descending colon to the rectum and is expelled through the anal canal.

Accessory glands and organs
Enzymes, bile, and hormones, which are vital to digestion, are produced by the:
• liver — filters and detoxifies blood, removes naturally occurring ammonia from body fluids, produces plasma proteins, stores essential nutrients, produces bile, converts glucose, and stores fat.
• gallbladder — stores and concentrates bile.
• pancreas — secretes more than 1,000 ml of digestive enzymes daily; houses alpha cells, which stimulate glucose formation in the liver, and beta cells, which secrete insulin to promote carbohydrate metabolism.

How digestive disorders develop
• Appendicitis — inflammation of the vermiform.
• Cholecystitis — inflammation of the gallbladder.
• Cirrhosis — widespread destruction of hepatic cells in the liver.
• Crohn’s disease — inflammation of any part of the GI tract.
• Hiatal hernia — defect in the diaphragm that permits a portion of the stomach to pass through the diaphragmatic opening into the chest cavity.
• Irritable bowel syndrome — characterized by chronic symptoms of abdominal pain, alternating constipation and diarrhea, and abdominal distention.
• Pancreatitis — inflammation of the pancreas; occurs in two forms:
–chronic pancreatitis (persistent inflammation)
–acute pancreatitis (inflammation causes tissue damage).
• Peptic ulcer — circumscribed lesion in the mucosal membrane of the upper GI tract.
• Ulcerative colitis — inflammation of the mucosa in the colon that causes ulcerations.
• Viral hepatitis — infection of the liver.