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Digestive System Discuss with your table partner: What are the different organs in the digestive tract (pathway through which food travels)? Give these organs in order. Mouth ___________ Stomach ________________ _________________ What organs are part of the digestive system even though they are not part of the digestive tract, because they produce digestive enzymes or other substances that are needed for digestion? ___________________________________________ Discuss with your table partner: The purpose of the digestive system is to break apart food polymers into their subunits. (Proteins into amino acids, Polysaccharides into sugars.) Mechanical digestion by the teeth does not break apart these bonds, which requires specific enzymes. But mechanical digestion plays an important role. How does grinding food into smaller pieces facilitate chemical digestion? Mechanical digestion __________________, which allows ____________ ______________________ Mouth • Mechanical digestion • Chemical digestion of starch The salivary glands produce amylase, an enzyme that breaks down ____________ . Esophagus: Tube that connects mouth to stomach. Peristalsis: Involuntary contractions of smooth muscle that _______ ____________________________________ Epiglottis: Flap that covers the larynx (upper windpipe) ________________________________ . Stomach o Mechanical digestion: muscular churning o Chemical digestion: Enzyme pepsin digests ______________________________ . Pepsin functional at low pH (acidic). Gastric juices (gastric= of the stomach): Contains _______________________________ in addition to pepsin. Mucus layer protects stomach from acid. Video: Movement of Food through the Digestive Tract Pancreas: secretes digestive enzymes and hormones. Trypsin: digests proteins Lipase: digests lipids Pancreatic amylase: digests starch Nucleases: digest nucleic acids Sodium hydrogen carbonate: creates alkaline conditions Video: Digestion of Different Foods http://www.youtube.com/watch?v=IxNpXO8gGFM Liver and Gall Bladder Liver: Produces bile (among many important functions) Bile breaks _____________________. (mechanical digestion rather than chemical) Gall Bladder: Stores bile Small Intestine • Small diameter (2.5 cm) • 6 meters long (provides a large surface) Mechanical digestion Chemical digestion ________________________ secreted into duodenum (first section of small intestine) Discuss with your table partner: What happens to food after it is digested? What must be present in the small intestines (where digestion is completed) for this to occur? Amino acids, sugars and fatty acids are __________ _____________________ _____________________ _____________________ _____________________. Small Intestine Villi Villi (singular: villus) are small projections in the small intestine, that _________________ ______________________________. Each villus has a ___________________ and lymph ducts. Digested food is absorbed for transport. Lymph vessels transport fats. Large Intestine (Colon) •6.5 cm wide •1.5 meters long •Indigestible materials pass into large intestine (such as cellulose) • ______________________ •Anaerobic bacteria that reside in colon synthesize vitamin K and some B vitamins Review with your table partner: What are some digestive enzymes and what substrates do they break down? Why does the stomach require a mucus lining? What are two important functions of the small intestine? What is the main function of the large intestine?