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Download Chapter 45: Processing Food and Nutrition The Digestive System
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Chapter 45: Processing Food and Nutrition The Digestive System Fig. 41-7 Small molecules Pieces of food Mechanical digestion Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Undigested material Food 1 Ingestion 2 Digestion 3 Absorption 4 Elimination Fig. 41-10a Tongue Sphincter Oral cavity Salivary glands Pharynx Esophagus Sphincter Liver Stomach Ascending portion of large intestine Gallbladder Duodenum of small intestine Pancreas Small intestine Small intestine Large intestine Rectum Anus Appendix Cecum Fig. 41-10b Salivary glands Mouth Esophagus Gallbladder Liver Pancreas Stomach Small intestine Large intestine Rectum Anus A schematic diagram of the human digestive system Fig. 41-11-3 Food Epiglottis up Tongue Epiglottis up Pharynx Esophageal sphincter contracted Glottis Larynx Trachea Epiglottis down Esophagus To To lungs stomach Glottis up and closed Esophageal sphincter relaxed Glottis down and open Esophageal sphincter contracted Relaxed muscles Relaxed muscles Stomach Contracted muscles Sphincter relaxed Fig. 41-12 Esophagus Sphincter Stomach 5 µm Sphincter Interior surface of stomach Small intestine Folds of epithelial tissue Epithelium 3 Pepsinogen 1 Pepsinogen and HCl are secreted. Pepsin 2 HCl Gastric gland 2 HCl converts pepsinogen to pepsin. 1 Mucus cells Cl– 3 Pepsin activates more pepsinogen. H+ Chief cells Chief cell Parietal cells Parietal cell Fig. 41-13 Carbohydrate digestion Oral cavity, pharynx, esophagus Polysaccharides Disaccharides (starch, glycogen) (sucrose, lactose) Protein digestion Nucleic acid digestion Fat digestion Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intestine Polysaccharides Pancreatic amylases Polypeptides Pancreatic trypsin and chymotrypsin DNA, RNA Fat globules Pancreatic nucleases Bile salts Maltose and other disaccharides Nucleotides Fat droplets Smaller polypeptides Pancreatic lipase Pancreatic carboxypeptidase Glycerol, fatty acids, monoglycerides Amino acids Epithelium of small intestine (brush border) Small peptides Disaccharidases Monosaccharides Nucleotidases Nucleosides Dipeptidases, carboxypeptidase, and aminopeptidase Amino acids Nucleosidases and phosphatases Nitrogenous bases, sugars, phosphates Fig. 41-15a Vein carrying blood to hepatic portal vein Muscle layers Large circular folds Villi Key Nutrient absorption Intestinal wall Fig. 41-15b Microvilli (brush border) at apical (lumenal) surface Lumen Blood capillaries Epithelial cells Basal surface Epithelial cells Lacteal Villi Key Nutrient absorption Lymph vessel Fig. 41-21 Stimulus: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood Stimulus: Blood glucose level drops below set point.
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