DIGESTIVE SYSTEM AND DIGESTION
I Overview
A. Muscular tube
B. Function
1. digestion : chemical and mechanical
2. absorption
II Nutrient molecules and absorption size* (review for final)
A. Carbohydrates --> polysaccharides --> monosaccharide (glucose)*
B. Lipids --> --> glycerol * + fatty acids*
C. Proteins --> polypeptides --> amino acids*
D. Nucleic acids
III Regions of gastrointestinal tract
A. Mouth
1. mechanical digestion
2. chemical digestion: salivary amylase breaks down carbohydrates and starches
B. Pharynx (throat)
C. Esophagus
1. peristalsis
D. Stomach
1. regions: cardiac, fundus, body, pyloric and rugae
2. chemical digestion : gastric glands
a. hydrochloric acid (HCl) : breaks down connective tissue and pepsinogen
b. pepsinogen �> pepsin : breaks proteins to amino acids
3. mechanical digestion
a. peristalsis (three layers of muscle in the wall)
4. absorption is minimal
E. Small intestine: major site of digestion and absorption
1. regions : duodenum, jejunum, ileum
2. chemical digestion
a. bile (liver and gall bladder) : breaks up lipids
b. pancreatic enzymes : pancreatic amylase, trypsin, lipase
c. intestinal enzymes : amylases, proteases
3. mechanical digestion : segmentation
4. absorption
a. increased surface area by foldings
1. plica circulares --> villi --> microvilli (brush border)
F. Large intestine
1. regions : cecum, ascending, transverse, descending, and sigmoid colon, rectum
2. reabsorption
At the end of this unit you should be able to:
- distinguish between digestion and absorption
- distinguish between mechanical and chemical digestion
- list the four groups of nutrient molecules and the units they must be broken into to be absorbed
- identify the six major regions of the digestive tube
- describe the types of digestion that occur in the mouth
- locate and distinguish between pharynx, larynx, and esophagus
- explain gastro-esophageal "acid reflux"
- identify the regions of the stomach
- discuss the chemical and mechanical digestion in the stomach
- locate the three major regions of the small intestine
- identify the accessory structures which add digestive juices to the duodenum
- discuss the chemical digestion that occurs in the duodenum
- compare peristalsis and segmentation
- discuss the structures of absorption in the small intestine
- identify and locate the regions of the large intestine
- state the function of the large intestine
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