Chapter 45: Processing Food and Nutrition The Digestive System

Fig IngestionDigestion Absorption Elimination Undigested material Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Small molecules Mechanical digestion Food Pieces of food

Fig a Cecum Anus Ascending portion of large intestine Gall- bladder Small intestine Large intestine Small intestine Rectum Pancreas Liver Salivary glands Tongue Oral cavity Pharynx Esophagus Sphincter Stomach Sphincter Duodenum of small intestine Appendix

Fig b Anus Liver Pancreas Small intestine Large intestine Rectum Stomach Gall- bladder A schematic diagram of the human digestive system Esophagus Salivary glands Mouth

Fig Larynx Trachea Epiglottis up Pharynx Tongue Glottis Esophagus Esophageal sphincter contracted Food To stomach To lungs Epiglottis down Esophageal sphincter relaxed Glottis up and closed Epiglottis up Esophageal sphincter contracted Sphincter relaxed Relaxed muscles Contracted muscles Relaxed muscles Stomach Glottis down and open

Fig Interior surface of stomach Esophagus Chief cells Small intestine Epithelium Stomach Sphincter Parietal cell Pepsinogen and HCl are secreted. HCl converts pepsinogen to pepsin. Pepsin activates more pepsinogen. Chief cell Folds of epithelial tissue Pepsin Sphincter Pepsinogen HCl H+H+ Cl – Parietal cells Mucus cells Gastric gland µm

Fig Oral cavity, pharynx, esophagus Stomach Lumen of small intes- tine Epithelium of small intestine (brush border) Carbohydrate digestion Polysaccharides Smaller polysaccharides, maltose Polysaccharides Maltose and other disaccharides Disaccharides Protein digestionNucleic acid digestionFat digestion Proteins Small polypeptides Pepsin Pancreatic amylases Salivary amylase Disaccharidases Monosaccharides Small peptides Amino acids Polypeptides Smaller polypeptides Pancreatic trypsin and chymotrypsin Pancreatic carboxypeptidase Dipeptidases, carboxypeptidase, and aminopeptidase DNA, RNA Pancreatic nucleases Fat globules Nucleotides Fat droplets Nucleosides Nitrogenous bases, sugars, phosphates Nucleotidases Nucleosidases and phosphatases Glycerol, fatty acids, monoglycerides Bile salts Pancreatic lipase (starch, glycogen)(sucrose, lactose)

Fig a Muscle layers Vein carrying blood to hepatic portal vein Villi Intestinal wall Key Nutrient absorption Large circular folds

Fig b Microvilli (brush border) at apical (lumenal) surface Key Nutrient absorption Blood capillaries Epithelial cells Villi Lymph vessel Basal surface Lacteal Epithelial cells Lumen

Fig Homeostasis: 90 mg glucose/ 100 mL blood Stimulus: Blood glucose level rises after eating. Stimulus: Blood glucose level drops below set point.