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Unformatted text preview: Physiology ō Digestion: Study Questions Synopsis : All aspects ō the human digestive process are addressed, from initial nutrient intake to the final stages ō absorption & elimination. In the study ō human anatomy, visual & three-dimensional renderings are ideal. So in addition to the audio lecture, overheads & text outline below, review the streaming video on digestion, w/c is located under “Content,” near the link to this page. Textbook readings: Chapter 3 gastro-intestinal (GI) system ( a.k.a. gut ): digestive system & its accessory organs 4 Processes ō Digestion : 1. motility : process ō moving food through the gut; peristalsis & segmentation (produces gut noises) 2. secretion : synthesis & release ō substances by cells in response to stimuli; moisten, lubricate, & digest food ( e.g. hormones, digestive enzymes, sweat) 3. digestion : chemical & mechanical breakdown ō foods & ō complex nutrient molecules into simpler components (for absorption) a. mechanically : chewing, churning b. chemically : hydrochloric acid (HCl), bile, enzymes 4. absorption : movement ō nutrients from intestinal lumen (interior ō gut) into mucosal cells (ō gut lining) Absorption Why is fat absorbed differently from other food molecules? Water soluble nutrients pass through mucosal cells into bloodstream. The blood is water-based, so it cannot carry fat soluble nutrients ( e.g. lipids & some vitamins). These pass into the lymphatic system . chemical difference ō fat & water : Fat cannot dissolve in water. 2 Pathways for Nutrient Molecules: mucosal cells → water soluble nutrients (protein, carbohydrates) → bloodstream mucosal cells → lipid/fat soluble nutrients → lymphatic system → liver Peristalsis What is peristalsis? Peristalsis :- rhythmic contraction ō (longitudinal/length-wise) circular muscles surrounding the gut to facilitate forward movement ō chyme (food mass)- rhythmic contraction ō bands ō muscle ringing the digestive tract that moves food forward through the GI tract- takes place mostly in small & large intestines What would happen if peristalsis came to a halt? Would digestion be possible w/ o it? If peristalsis came to a halt, then there is no movement in the gut & digestion would stall. One cannot swallow against gravity. Food is there, but there is no process. Digestion I. Mouth a. Chewing b. Saliva Mouth What function does chewing serve? What does saliva do? Is it worth chewing your food well? Chewing : starts mechanical breakdown ō food into smaller particles while mixing w/ digestive juices/secretions ( e.g. saliva) to begin chemical digestion ō starch (longer chew → sweeter taste) ; 1 st stage ō digestion Saliva : digestive juices that moistens/lubricates food so it is easier to swallow; contains amylase, w/c is an enzyme that breaks down amylose (primary form ō starch) , & lipase Yes, it is worth chewing food well because non-chewing delays digestion....
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- Spring '08
- Large intestine