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A tour through the digestive system

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Trevor Heard

on 18 January 2013

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Transcript of A tour through the digestive system

A journey through the digestive system Where does our lunch go? Oral Cavity Next class: and associated organs Pelvic Cavity -now that we know the path that food takes through our bodies, next we will take a look at the enzymes, digestive juices, and bacteria that assist and speed up the process of digestion Lips, Tongue and Teeth Includes both the physical and chemical processes that reduce food to small soluble molecules that can be absorbed. Absorption: The entrance of these molecules across the gut lining (especially across microvilli - the tiny, finger-like projections of the small intestine) Key Terms Digestion: Only certain substances can be absorbed: There are two types of digestion: Chemical digestion: -Chemical breakdown of food using enzymes Physical digestion: -Physical breakdown of food into smaller pieces
-Increases surface area so enzymes can work on them All aboard!! - FREE! The oral cavity is the fancy term for your mouth. Its primary function is for storage of food while it is being chewed. It is also the place where saliva is mixed with food. Lips: Teeth: Tongue: Salivary Glands Salivary glands produce saliva Pharynx: -Back of the throat where oral and nasal cavities join. -Where swallowing occurs Key Terms: Elimination (defacation): All contents of food that cannot be digested exit the body by the process of elimination, or, defacation (pooping) Along the way, you will learn the functions of the various digestive structures Lets begin in the oral cavity.... You are now about to embark on a tour of the digestive tract: the path that food follows through your body as it gets digested. (For an extra 100 RMB, you will NOT be digested on this tour!!) Epiglottis: -Flap of tissue that closes off the opening of the trachea when we swallow food -keeps food from entering the air passage Wall of the esophagus Esophagus: -tube leading from the pharynx to the stomach -food moves down the esophagus due to the process of peristalsis: a rhythmical contraction of the muscles in the esophageal wall Peristalsis: -smooth muscle lining the esophageal wall pushes food down -also occurs along the intestinal tract a) amino acids of proteins b) sugars of carbohydrates c) glycerol and fatty acids of fats d) some minerals and water -hold food in the oral cavity -help direct food onto teeth -start the process of physical digestion (break food down into smaller pieces) -directs food onto teeth -pushes chewed food to the pharynx -saliva moistens food, and contains enzymes that begin chemical digestion of carbohydrates -there are 3 different salivary glands: Abdominal Cavity Stomach Liver Pancreas Gall Bladder Lower Abdominal Cavity Small Intestine Large Intestine Rectum Anus Appendix: Cecum: Ascending Colon: Transverse Colon Descending Colon Sigmoid Colon Duodenum Cardiac Sphincter (lower esophageal sphincter Pyloric Sphincter Villi, Microvilli, and Lacteals: -J-shaped organ which stores and churns food -churning helps physical digestion of food -churning results in a product called "acid chyme" -chemical digestion of proteins begins in the stomach -band of muscle which closes off the top of the stomach -keeps stomach acid from entering the esophagus -band of muscle which closes off the bottom of the stomach -allows small amounts of chyme to enter the intestine -first 10 inches of small intestine -in the duodenum, enzymes from the pancreas enter and help chemical digestion of all 3 food groups (proteins, fats, carbohydrates) -bile enters the duodenum from the gall bladder and emuslifies fats -the pancreas produces digestive enzymes and sodium bicarbonate -sodium bicarbonate helps neutralize the acid chyme Gall Bladder: -the gall bladder stores bile -bile emulsifies fats (breaks fat down into small fat droplets) in the duodenum -bile is NOT an enzyme! -the liver is an essential organ with several different functions: 1) produces bile 2) destroys old red blood cells and converts hemoglobin to a product in bile 3) stores glucose as glycogen after eating, and breaks down glycogen to glucose between eating to help maintain glucose (sugar) level of blood 4) produces urea from the breakdown of amino acids (deamination) 5) makes blood proteins from amino acids 6) detoxifies the blood by removing poisinous substances and metabolizing them (converting them into harmless substances) -final digestion of food -absorption of nutrients through the villi -small intestine is specialized for absorption of nutrients -is long (about 7 meters!) with convoluted (folded) walls which increases surface area (more surface area means more surface for absorption) -walls have villi (tiny finger-like projections) along the walls (singular - villus) -villi themselves have even tinier microvilli -within each villus are small blood vessels and a small lymph vessel called a lacteal -the lacteal absorbs fluids and returns it to the veins -found at the junction of the small intestine and large intestine -no known function in humans -the colon (large intestine) is responsible for absorption of water from undigested food -it is divided into 4 parts: -first is the ascending colon -enlarged portion of the colon -stores undigested food temporarily -also called "anal sphincter" -bands of muscle which allow undigested wastes (poop) to exit the body Wow! We made it! -that was quite the journey, I don't think we would want to do it again (kind of smelly!), but we did learn a lot -we now know the major function of most of the structures of the digestive system
-I hope you enjoyed the tour!
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