2 Digestive ProcessesIn order for our bodies to use the food we eat to grow, energize, and repair our cells, 5 digestive processes have to occur.These include:IngestionMovementDigestionAbsorptionEgestion (excretion)
3 Digestive ProcessesThese processes occur at different locations along the digestive tract, which is a continuous tube from mouth to anus.We are going to discuss what happens at each site as we go through the stages.It will be useful to copy the following concept map and to keep adding to it as we add more details to help you stay organized.
4 NOTE: This should be a straight line in your notes SmallIntestineStomachLargeIntestineEsophagusTongueRectum/AnusMouth/ThroatTeethSalivary Glands
5 Digestive System Includes organs which perform digestion tasks: Digestive Tract (Gastrointestinal Tract, G. I. Tract) includes: mouth, esophagus, stomach, small intestine, large intestine or colon, and anus.Accessory Structures include:, tongue, salivary glands, liver, gall bladder and pancreas.
6 DigestionThe process in our bodies that breaks down food for use by our cells. This is done in two ways:Mechanical: our teeth chewing through the foodChemical: enzymes breakdown food into absorbable molecules.
7 Mouth (where it all begins) Hard PalateFour main parts of the mouthTeethTongueSalivary GlandsHard and Soft PalatesUvula
8 Mouth Teeth (Chewing) How many teeth in adult humans? Mechanical DigestionAre covered by enamel, the hardest structure of the bodyTheir movements slice, tear, grind and mix foodIncisors: snap off pieces of foodCanine: tearing pieces apartPremolars & molars: grind food to a pasteHow many teeth in adult humans?
9 Tongue Floor of oral cavity Composed of voluntarily controlled muscle tissueRole: Guides food during chewing and swallowingMajor taste buds are embedded here.Salty, sweet, sour, bitter
10 Salivary GlandsRelease saliva in response to the smell, taste, and thought of foodFirst example of chemical digestion:Contains Amylase: an enzyme that begins breakdown of starch into simple sugars, like glucose or table sugar.Interesting Fact: We secrete about 1-2L of saliva per day!
11 Hard & Soft Palates Separate mouth from nasal cavity, so food doesn’t go up your nose!Located at the roof of your mouth.Uvula (dangles)Just beneath the soft palatePrevents food from entering nasal passages by raising up.
13 Recap (Mouth) Food enters Teeth rip, tear, and chew into smaller pieces to swallowAt the same time, Salivary Glands are stimulated to release saliva which contains amylase.Tongue pushes bolus to back of pharynx (throat) and the uvula elevates, closing off the nasal passage. The bolus now pushes the epiglottis which closes the opening of the larynx, preventing the food from entering the wrong tube, which results in choking
14 EsophagusMuscular tube which extends from pharynx (throat) to the stomachSwallowing initiates peristalsis, a wave of contraction which initiates just above the “bolus” (substance) and moves it towards the stomach.This movement also occurs in the stomach and in the intestines.
15 Esophagus Secretes mucus (along with the rest of the digestive tract) This lubricant decreases the likelihood of the esophagus getting damaged by any sharp edges from the food entering.Mucus also protects esophagus from acid and enzymes in gastric juice if reflux were to occur.
16 NOTE: This should be a straight line in your notes SmallIntestineStomachMechanical: PeristalsisLargeIntestineEsophagusTongueRectum/AnusMouth/ThroatMechanical: ChewingChemical: Starch/AmylaseTeethSalivary Glands
17 Stomach Separated from esophagus by the Gastro esophageal sphincter Expandable muscular J-shaped sac that can hold up to 2-4 liters of food and liquidSecretes mucous to protect lining cellsContents are held in the stomach by the pyloric sphincter, ring of circular muscle, which separates the stomach from upper small intestine
18 Stomach3 FunctionsStores food and releases it gradually into the small intestineAssist in mechanical breakdown of food by peristalsis and contractions of muscular wallsChemical breakdown of food by enzymes and other substances.
19 Stomach Secretions (continued) Gastrin: hormone that stimulates secretion of Hydrochloric acid (HCl)Pepsinogen: inactive form of enzyme is activated by HCl and transformed into pepsin which helps breakdown proteins into amino acids (smaller units).
20 StomachFood is gradually converted into a thick liquid called chyme which consists of partially digested food and digestive secretions.Chyme is propelled towards small intestineThe Pyloric sphincter lets a teaspoon of chyme into the small intestine during each contractionTakes around 2-6 hours to empty stomach
21 NOTE: This should be a straight line in your notes Mechanical: Muscle ContractionsMechanical: PeristalsisSmallIntestineStomachMechanical: PeristalsisChemical: Pepsin (Proteins), HClLargeIntestineEsophagusTongueRectum/AnusMouth/ThroatMechanical: ChewingChemical: StarchTeethSalivary Glands
22 Small Intestine (S. I.) Narrow tube (1-2 inches in diameter) Longest part of digestive tractSplit into three parts: duodenum, jejunum, and the ileumFunction: to digest food into small molecules and absorb into blood stream and lymph vessels.
23 Small Intestine (S. I) Helped by three other sources: 1. Liver: Has many functions in our bodies. In digestion, it produces bile which is stored in the gall bladder, then released in the S. I.Bile is made up of bile salts, water, and other salts and assist in the breakdown of lipids.
24 Small Intestine (S. I.)2. Gall Bladder stores bile until it’s needed for digestion
25 Small Intestine (S. I.) Located between stomach and S. I. 3. PancreasLocated between stomach and S. I.Cells produce pancreatic juice which neutralizes the acidic chyme it receives from the stomachDigests carbohydrates, proteins, and lipidsContains water, sodium bicarbonate, and many enzymesYouTube - Pancreas - "Weird Al" Yankovic
26 Small Intestine (S. I) Pancreas (cont’d) Enzymes include: Amylase CarbohydratesLipase LipidsProteases Proteins and peptides
27 Small Intestine (S. I.)Specialized cells within the wall complete the process. At the same time, nutrients are absorbed into the blood stream.The numerous folds and projections, called villi, give the internal surface area a much larger surface for absorption.
28 Small Intestine (S. I.)The area of absorption is also increased by the millions of microvilli.
29 NOTE: This should be a straight line in your notes Mechanical: PeristalsisBile emulsifies lipidsAlcohol absorbedChemical: Amylase-CH2OLipase-LipidsProteases-ProteinsMechanical: Muscle ContractionsPeristalsis (3 layers)SmallIntestineStomachMacro & micronutrients absorbedMechanical: PeristalsisChemical: Pepsin-ProteinsHCl: pH-2(gastric juices)LargeIntestineEsophagusTongueRectum/AnusMouth/ThroatMechanical: ChewingChemical: Amylase-StarchTeethSalivary Glands
30 Are We There Yet? Almost… While the nutrients are being absorbed by these cells, chyme is being mixed back and forth by segmentation movements within the small intestine.When absorption is complete, undigested material moves into the large intestine.
31 Large Intestine (L. I.) Is about 5 feet long and 3 inches in diameter in adultsTwo parts:Colon(for most of its length)Rectum: the final 6”Receives leftovers of digestion: water mixture, undigested fat and proteins, indigestible fibers
32 Large Intestine (L. I.)Contains large populations of bacteria that thrive on the unabsorbed nutrients and are also responsible for synthesizing important vitamins for the body (B12, riboflavin, K).Remaining water, salts, and vitamins are reabsorbed by cells in the L. I.
33 NOTE: This should be a straight line in your notes Mechanical: PeristalsisBile emulsifies lipidsMechanical: Muscle ContractionsPeristalsis (3 layers)Chemical: Amylase-CH2OLipase-LipidsProteases-ProteinsSmallIntestineStomachMacronutrients absorbedMechanical: PeristalsisChemical: Pepsin-ProteinsHCl: pH-2(gastric juices)LargeIntestineEsophagusTongueRemaining water, salts and vitamins absorbedRectum/AnusMouth/ThroatMechanical: ChewingChemical: Amylase-StarchTeethSalivary Glands
34 Large Intestine (L. I.)Leftover material is condensed into semisolid feces which are transported to the rectum by peristaltic movements.Expansion of the rectum stimulates the urge to defecate which is initiated voluntarily after age 2.
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