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Structure of Cellulose Fig. 5.7 Glucose occurs in two conformations, and . In cellulose, every other glucose is “upside down” making it impossible for amylase (enzyme found in animals) to digest it. Very few animals have evolved the enzyme cellulase , but many microbes have this enzyme.
Digestive System Chapter 14 Figure 14.1 Pharynx • Passageway for food and air • Participates in swallowing Esophagus • Moves food from pharynx to stomach Salivary glands • Saliva moistens food • Bicarbonate maintains pH • Amylase digests starch • Lysozyme inhibits bacteria ACCESSORY ORGANS: Liver • Produces bile • Performs various functions associated with processing and storing nutrients Pancreas • Secretes digestive enzymes into small intestine • Secretes bicarbonate into small intestine to neutralize stomach acid Gallbladder • Stores and concentrates bile Mouth • Teeth chew food • Tongue positions and tastes food ORGANS: Appendix • No known digestive function Stomach • Stores and mixes food • Begins chemical digestion of protein by enzymes and acid • Regulates delivery to the small intestine Anus • Expels undigested material Rectum • Passageway for feces Sigmoid colon • Stores feces Large intestine • Absorbs the last of the water and nutrients • Stores waste material Small intestine • Digests proteins, fats, and carbohydrates • Absorbs most of the water and nutrients • Secretes digestive hormones and enzymes
Gastrointestinal (GI) Tract Wall Figure 14.2 Lumen Circular layer Longitudinal layer Lymph vessel Serosa • Connective tissue outer covering • Protects and anchors the digestive tract Mucosa • Mucous membrane layer • Lines the digestive tract Submucosa • Connective tissue layer • Contains blood vessels, lymph vessels, and nerves Muscularis • Two layers of smooth muscle • Responsible for motility of the digestive tract Vein Artery Nerve
Accessory Organs: Aid Digestion and Absorption Figure 14.10 Esophagus Liver • Produces bile (water and electrolytes, cholesterol, bile salts, lecithin, and pigments) Gallbladder • Stores and concentrates bile • Delivers bile to the duodenum via the common bile duct Pancreas • Secretes enzymes (proteases, amylase, lipase) • Produces sodium bicarbonate • Delivers these products to the duodenum via ducts Stomach Pancreatic duct Common bile duct Duodenum
Accessory Organs: Aid Digestion and Absorption Figure 14.11