The Human Digestive Tract
The Mouth salivary glands (parotid, sublingual, submaxillary) - produces saliva --->lubricate food ---> dissolves food particles ---> allows us to taste food --->contains amylase (enzyme) breaks down starch---> disaccharide = chemical digestion teeth are important for mechanical digestion
Teeth different shapes have different functions. incisors-cut the food. canines (or cuspids)-tear and shred food premolars (or bicuspids)- tear, crush, and grind the food. molars -crush and grind food
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The Esophagus - mucin is secreted by cells (lubricate path) - lined with circular & longitudinal muscles - work together to push food down peristalsis - wave like muscular contraction that moves food
If you found a skull of an unknown animal, what could you examine so that you could hypothesize about its diet? Explain with an example. Infer how food reaches an astronaut s stomach when s/he is floating in zero gravity. Your friend is convinced that digestion begins in the stomach. Is this true or false? Explain and include two facts to support your answer. 6
The Stomach esophogeal (cardiac) sphincter found before stomach - thickened muscular ring - controls movement of food in & out of stomach
The Stomach - J-shaped with lots of ridges (rugae) to allow for expansion - gastric juices contain mucus, hydrochloric acid, & pepsin mucus - protects stomach lining HCl - kills harmful substances (ph1-3) - activates pepsin pepsin - enzyme that cuts proteins into shorter chains of aa (polypeptides)
The Stomach - muscle layers ---> work to mechanically by churning to breakdown food into: chyme - thick liquid found in stomach
The Stomach - pyloric sphincter found at end of stomach - controls movement of food out of stomach into sm intestine
Small Intestine - 6-7 m long - muscles moves food along (peristalsis) - primary functions: chemically breakdown chyme & absorb nutrients - a lot of surface area is needed!
Small Intestine how does the intestine increase surface area for absorption of nutrients? - folds in intestine covered by villi (finger-like extensions) - microvilli on villi - capillaries in villi absorb nutrients
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3 sections of small intestine: 1. duodenum - chemical breakdown is primary - pancreas & gall bladder empty enzymes to breakdown 2. jejunum - breaks down proteins & carbohydrates 3. ileum - absorbs remaining nutrients - pushes undigested material along
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caecum - first section - appendix is attached to it --> role: Bacteria replacement! The Large Intestine
Watch this video about the latest research on gut bacteria (microbes).
The Large Intestine (cont d) colon - water is absorbed - bacteria (E. coli) help to break down material ---> produce vitamin B-12 & K - final result is feces - feces passes through rectum & anal canal by peristalsis anal sphincter - allows for control of elimination
Katie Couric s first husband died of colon cancer. He was too embarrassed to have a colonoscopy when he first had symptoms (eg., rectal bleeding). Katie wanted to encourage people to get a colonoscopy before it was too late so she had the procedure on TV!! Let s take a look! As you watch, notice how the inside of the large intestine looks. 20
Colonoscopy 21
The Pancreas secrete enzymes into the small intestines. act on carbohydrates (amylase), fats (lipase), and peptides (proteases) secretes a basic solution (bicarbonate) to neutralize chyme (---> making it slightly basic)
Liver The Liver & Gall Bladder
The Liver & Gall Bladder Liver continuously makes bile - speeds up fat digestion - bile emulsifies fat = physical digestion - smaller droplets of fat chemically broken down by lipases
The Liver & Gall Bladder Other important functions of the liver include: - breaks down old RBC - storage of excess chemicals from blood eg. sugar, vitamins A, D, E, K - breaks down amino acids for storage of - detoxifies poisons and drugs (including alcohol) gall bladder - stores bile
Classwork/Homework 1. Read 411-415, 418 2. Complete pg 419 #1, 6, 7, 8, 10, 12 26