Functions of Small and Large Intestine

Digestive System Functions

• Chemical digestion of food takes place in the small intestine
• Food is absorbed through the mucosa in the small intestine
• The large intestine dries out indigestible food residue by absorbing water and electrolytes, and then eliminates the residues from the body as feces

Accessory Digestive Glands

• The pancreas produces enzymes important for digestion, including:
  • Trypsin and chymotrypsin (break down proteins)
  • Amylase (breaks down carbohydrates)
  • Lipase (breaks down fats)
• The gallbladder stores and concentrates bile, which is produced by the liver and aids in the digestion of fats

Manifestations of Diseases of the Gastrointestinal Tract

• Dyspepsia: upper abdominal or epigastric symptoms like pain, discomfort, fullness, bloating, early satiety, belching, heartburn, regurgitation, and "indigestion"
• Belching: involuntary or voluntary release of gas from the stomach or esophagus, caused by swallowing air or taking carbonated drinks
• Anorexia: loss of appetite
• Unexplained weight loss or weight loss without trying
• Flatus: expulsion of gas (H2, CO2, methane) per anus, caused by swallowed air and bacterial fermentation of undigested carbohydrates
• Nausea: vague, intensive, disagreeable sensation of sickness or "queasiness"
• Vomiting: projectile reflux of gastric contents preceded by nausea
• Diarrhea: increased frequency of bowel movement, increased stool liquidity, and fecal urgency
• Constipation: 2 or fewer bowel movements/week, or excessive difficulty and straining at defecation
• Gastrointestinal bleeding: manifestation of bleeding in the gastrointestinal tract
• Hiccups: sudden, involuntary contraction of the diaphragm, accompanied by a characteristic sound
• Dysphagia: difficulty in swallowing or painful swallowing
• Regurgitation: return of food or other substances from the stomach to the mouth

Helicobacter Pylori Disease

• Gram-negative, microaerophilic bacterium found in the stomach
• Implicated in stomach cancers and duodenal ulcers
• May be asymptomatic
• Symptoms: abdominal pain, nausea, bloating, belching, vomiting, or tarry stools
• Diagnosis: biopsy, blood antibody test, stool antigen test, or carbon urease breath test

Peptic Ulcer Disease

• Break in the gastric or duodenal mucosa that arises when normal mucosal defensive factors are impaired or overwhelmed by aggressive luminal factors
• Statistics: 1.3:1 (male:female) for gastric ulcer, 30-55 years old for duodenal ulcer
• Etiology: H. pylori infection, drugs (NSAIDs, aspirin), and pylori gastritis
• Treatment: pylori gastritis treatment, antibiotics, and antacids

Diseases of the Small Intestines

• Malabsorption: disruption of digestion and nutrient absorption
• Appendicitis: infection or inflammation of the appendix, usually caused by fecalith material, tumor, or destruction

Diseases of the Colon

• Inflammatory Bowel Disease: Ulcerative Colitis and Crohn's Disease
• Diverticular Disease of the Colon: Diverticulitis
• Ulcerative Colitis: chronic recurrent disease characterized by diffuse mucosal inflammation involving only the colon
• Crohn's Disease: chronic recurrent disease characterized by patchy transmural inflammation involving any segment of the gastrointestinal tract
• Diverticulitis: perforation of a colonic diverticulum results in an intra-abdominal infection