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Questions and Answers
What is the main function of the villi in the small intestine?
What is the main function of the villi in the small intestine?
What is the primary function of the colon in the absorptive process?
What is the primary function of the colon in the absorptive process?
What is the main component of feces in terms of nutrient content?
What is the main component of feces in terms of nutrient content?
What is the role of bile in fat absorption?
What is the role of bile in fat absorption?
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What is the approximate length of the small intestine?
What is the approximate length of the small intestine?
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What is the primary function of the colon?
What is the primary function of the colon?
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What is the approximate composition of feces?
What is the approximate composition of feces?
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What is responsible for the brown color of feces?
What is responsible for the brown color of feces?
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What is the result of gastric motor activity slowing down with age?
What is the result of gastric motor activity slowing down with age?
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What is one of the roles of the gastrointestinal tract in fluid and electrolyte balance?
What is one of the roles of the gastrointestinal tract in fluid and electrolyte balance?
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Study Notes
Gastrointestinal Tract
- The stomach contains pepsin, which is necessary for protein digestion, and HCL acid, which aids in the pre-digestion of food
Small Intestine
- The small intestine is 2.5 cm (1 inch) wide and 6 meters (20 feet) long, and fills most of the abdomen
- It has three parts: duodenum (10 inches), jejunum (8 feet long), and ileum (12 feet long)
- The ileocecal valve prevents backward flow of fecal contents from the large intestine to the small intestine
- The vermiform appendix is located near the ileocecal valve and has no known function
Large Intestine
- The large intestine is 6 cm (2 ½ inches) wide and 1.5 meters (5 feet) long
- It has three parts: cecum, colon, and rectum
- The rectum is 17-20 cm (7-8 inches) long and leads to the anal canal
- The anus is controlled by an internal smooth muscle sphincter and an external striated muscle sphincter
Digestive Function
- The primary function of the digestive system is to break down food particles into molecular form, absorb nutrient molecules, and eliminate waste products
- The majority of digestion occurs in the small intestine through the action of pancreatic and intestinal secretions (enzymes) and bile
Carbohydrate Digestion
- Carbohydrate digestion begins in the mouth with ptyalin, which breaks down polysaccharides to disaccharides
- Intestinal enzymes (maltase, lactase, sucrase) break down disaccharides to monosaccharides (glucose, galactose, fructose)
Protein Digestion
- Protein digestion begins in the stomach with pepsin, which breaks down proteins to polypeptides
- In the small intestine, trypsin breaks down polypeptides into peptides and amino acids
Fat Digestion
- Fat digestion requires emulsification into small droplets, which is facilitated by bile from the liver
- Pancreatic lipase breaks down fats into glycerol and fatty acids
Absorption
- The intestinal wall has folds covered by villi, which increase the absorptive area
- 90% of absorption occurs in the small intestine through active transport or diffusion
- Reabsorption of water, electrolytes, and bile occurs mainly in the ascending colon
Colonic Function
- The colon's primary function is to reabsorb water and electrolytes
- Waste material passes into the terminal ileum and slowly into the proximal portion of the right colon through the ileocecal valve
- Slow, weak peristalsis moves the colonic contents along the tract
Feces Composition
- Feces consist of undigested foodstuffs, inorganic materials, water, and bacteria
- Feces are 75% fluid and 25% solid material
- The brown color of feces results from the breakdown of bile by intestinal bacteria
Age-Related Changes
- Teeth are worn down with age, and the jaw may be affected by osteoarthritis
- There is a significant loss of taste buds with age
- Xerostomia (dry mouth) is common in older adults
- Walls of the esophagus and stomach thin with age, and secretions lessen
- Production of hydrochloric acid and digestive enzymes decreases
- Gastric motor activity slows, and movement of contents through the colon is slower
- Anal sphincter tone and strength decrease
Fluid and Electrolyte Balance
- GIT secretions contain electrolytes, and severe fluid and electrolyte imbalance may occur with excessive losses of gastrointestinal fluids
- Examples of imbalances include:
- Na+ and K+ deficits due to vomiting, diarrhea, gastric suctioning, or intestinal fistula
- Ca++ and Mg++ deficits due to malnutrition, malabsorption, or intestinal fistula
- Metabolic alkalosis due to loss of gastric acid by suctioning or persistent vomiting
- Metabolic acidosis due to loss of bicarbonate-rich intestinal secretions by severe diarrhea or fistula
Other Functions of the GIT
- The GIT supports bacterial growth and has a role in antibody formation
- Intestinal bacteria synthesize vitamins
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Description
Learn about the digestive functions of the stomach, including pepsin and HCL acid, and the structure and parts of the small and large intestines. Understand the roles of the duodenum, jejunum, and ileum in the digestive process.
