Digestive System Notes
Function of the Digestive System
How does the Digestive-System work?
Movement of Material through GI Tract - Factors affecting rate (ie how much you eat) (will vary among people)
- Stomach--About 20 min after you start eating, chyme is released by the stomach.
- Once you finished eating, it takes 4-6 hours to remove all the food from the stomach.
- Small intestine—Chyme leaves the small intestine after 2 hours.
- Total elimination of chyme from small intestine is about 5 hours.
- Large intestine—Chyme leaving the large intestine after 30 hours you eat.
- Total elimination from large intestine is variable depending on when you defecate the bulk amount.
Large intestine - Absorbs water
- Fermentation occurs in the large intestine
Main mechanism of absorption is active transport of various ions and particles. Constipation—too much water absorbed from the material. The material stays in the colon. Constipation caused by dehydration, lack of fiber (causes less peristalsis), and smooth muscles GI tract for elders wears out. Constipation occurs from decreased peristalsis. Diuretics and pain killers slow down smooth muscles causing less peristalsis and constipation - Treatment: more fiber, laxatives (magnesium/aluminum holds water in the lumen of the tube or in the waste material) Mg and Al are particles that we don’t absorb, water follows the particles, pulling more water out of the body and onto the stool.
Diarrhea—too much fluid in the lumen of the tube or the stool and not absorbed. Caused by bacterial infection
Cholera-secrete chloride ion into the intestine and you lose too much water. - Treatment: don’t drink pure water. You need particles (Na, glucose) that can be absorbed, causing the water to follow (being absorbed)
Pancreas Key enzymes released by pancreas - Amylase from pancreas
- Breaks down bigger sugars into smaller sugars
- Takes any polysaccharides and break it up to oligosaccharides.
- Oligosaccharides broken down into monosaccharide by enzymes on the microvilli from the epithelial cells
- Microvilli on the epithelial cells increases surface area, which gives more absorption
- Monosaccharide goes against the gradient from the lumen to the epithelial cell
Fiber is a polysaccharide consisting of cellulose. - We do not have an enzyme that breaks down oligosaccharides like cellulose.
- This means that the fiber is going to move through the system without being digested and absorbed.
- Fiber is good because it increase the mass in the GI tract, which stretches the wall of the GI tract, creating better bowel movement. The muscular layer of the GI tract produces a stronger peristalsis when the GI tract is stretched.
What is lactose intolerance?
Protein and Lipid Digestion
Digestive System--Back to Learn Physiology
Digestive System - Back to SG Learn Online
|
