2I. IntroductionDigestion is the process of altering the physical state and chemical composition of food, so that it can be absorbed.The digestive tract is also called the gastrointestinal tract or alimentary canal.
4II. Digestive Organs Oral cavity (mouth) hard palate and soft palate form roofUvula – cone-shaped projection that keeps food out of nasal cavity during swallowingTongue –mixes food particles with saliva and moves food toward pharynx; also aides in speechPapillae – rough projections on surface of tongue that help handle food and contain taste buds (tip-salty/sweet; sides-sour; back-bitter)Salivary glands – secrete saliva and are located near the ears and tongue; saliva helps moisten food particles and begins the chemical digestion of carbohydrates
6II. Digestive Organs (cont) Teethbreak food into smaller pieces creating more surface area for digestion32 total; covered with enamel, the hardest substance in the bodyBegin physical digestionPharynx (throat)connects oral cavity to esophagusEsophaguslong tube (~25 cm) dorsal to trachea that delivers food to stomachmade of smooth muscletransports food by peristalsis (rippling contractions) and secretes mucus
8II. Digestive Organs (cont) StomachJ-shaped organ with a capacity of 1 liter or morethe stomach wall has folds called rugaeMain site of physical digestion, which is almost completed in the stomach by the peristalsis waves which churn the foodchemical digestion of proteins begins in the stomach and is completed in the small intestinesgastric juice – combination of pepsin, pepsinogen, hydrochloric acid, and mucus; pepsin begins the digestion of protein; pepsinogen reacts with hydrochloric acid and changes into pepsinLittle to no fat digestion takes place in the stomach.Food leaves the stomach as a liquid called CHYME
9II. Digestive Organs (cont) Stomachvery limited amount of absorption occurs here; water, some drugs (ex. Aspirin), and alcoholThe cardiac sphincter (lower esophageal sphincter)– is located where the esophagus connects to the stomach. It is a muscular valve which prevents food and gastric enzymes from being pushed back into the esophagus.The pyloric sphincter – is located where the stomach connects to the small intestine. It prevents backwash from the Small intestine into the stomach.
11II. Digestive Organs (cont) Liverweighs ~3lbs. and is located in the upper right of abdominal cavityreddish-brown in color because it filters the blood,and is divided into right and left lobesfunctions in protein, carbohydrate, and lipid metabolismstorage area for glycogen, iron, vitamins A, D, and B12filters blood, destroying damaged RBCs and foreign antigensremoves toxic substances such as alcohol from blood
12II. Digestive Organs (cont) Bile – is a yellowish-green enzyme that helps the body digest fats by breaking the fats down physically.Fats and oils stick together and move away from water this makes them difficult to digest because the enzymes can not get around the fats.Bile causes EMULSIFICATION to happen – which means it separates the fats into tiny droplets which can now be chemically digested.Bile is made in the liver, stored in the gall bladder (which is why it is green), and transported to the pancreas and then the duodenum by the bile duct.
14II. Digestive Organs (cont) Pancreaslies posterior to greater curvature of stomachsecretes pancreatic juice into small intestinepancreatic juice contains enzymes that digest carbs, fats, nucleic acids, and proteins
16II. Digestive Organs (cont) Small intestinebetween stomach and large intestinemany loops and coilsinner wall lined with villi – projections that increase the surface area for absorptionsecretes enzymes that break down food and receives secretions from the pancreas and livercompletes digestion of nutrients in chymeabsorbs 90% of products of digestiontransports wastes into large intestine
17II. Digestive Organs (cont) Small intestine - Main site of chemical digestion.There are 3 sections to the small intestines:Duodenum which is the first section and is 25 cm long. Pancreatic enzymes and bile are released into the small intestine in this section.Jejunum is the second section and is about 2.5m (8 ft) long and passes imperceptibly into theIleum, which is the final section and is about 4m (12 ft).
19II. Digestive Organs (cont) large intestinealso called colonreabsorbs water, vitamins and electrolyteslast stages of chemical digestion occur here through bacterial, rather than enzymatic actionforms and stores feces (FYI - feces is ~75%water and the odor results from bacteria products; feces is composed of water, salts, bacteria (such as E. coli), and undigested food)feces formation/defecation: peristaltic waves occur only 2-3 times a day in the large intestine; the waves produce mass movements, usually after a meal
20II. Digestive Organs (cont) Large intestine is made up of 3 sections as well –The first is the ascending colon which connects to the small intestine and has the appendix coming off of it.The second is the transverse colon.The third is the descending colon.Rectum – expandable organ for temporary storage of fecesAnus – final exit lined with keratinized epidermal tissue
22Enzymes of the digestive system SOURCEDIGESTIVE ACTIONAmylaseSalivary glands, pancreasBegins digestion of carbs; polysacc to disaccpepsinstomachBegins digestion of proteinlipaseSmall intestine and pancreasdigestion of lipids; triglycerides to fatty acids and glycerolchemical
23Enzymes of the digestive system bileLiverPhysical digestion of fatsproteolytic enzymes: ex. trypsinPancreasBreaks down proteins into peptidespeptidasesSmall intestineBreaks down peptides into amino acidssucrase, maltase, lactaseBreaks down disacc into monosacc
24Digestive System Key Terms Peristalsis: waves of rhythmic contractions that aid in digestive processesRugae: folds in the stomachChyme: partially digested food mixed with stomach acid (stomach to intestines)Sphincter: ring-like muscles that maintain constriction ( like valves)Villi: projections of a membrane that increases surface area
25Digestive System Key Terms Bolus: chewed up foodMastication: the act of chewingEnzymes: proteins that act as catalysts in the bodyAmylase: enzyme that breaks down carbohydratesPepsin: enzyme that breaks down proteinLipase: enzyme that breaks down fatsGallbladder: small organ that stores bile
26NutritionNutrition is the process by which the body takes in and utilizes necessary food sources (nutrients).
27Metabolism Cellular Metabolism: The chemical and physical reactions that take place in the cell.Normally involves an enzyme to synthesize or break down molecules (CHO, Lipid, PRO) for cell use.Example: Mitochondria making energy for the body.
28Nutrients Carbohydrates: Organic Supply energy for cellular processes Sources: starch from grains, veggies; glycogen from meat; disaccharides from cane sugar; monosaccharides from honey and fruitsCellulose- sugar that cannot be digested, provides bulk (called fiber) which assists movement thru digestive systemRDI (Recommended Daily Intake) grams
30Nutrients Lipids: Organic Supply energy for cellular processes and building cellular structuresFats, oilsSources: Meats, eggs, milk, lard, seeds, nuts, plant oilsSaturated fats should account for no more than 10% of diet
32Nutrients Proteins: Organic Made of amino acids Imp. Components of enzymes, clotting factors, keratin in skin and hair, collagen in connective tissue, muscle components (actin/myosin) hormones, antibodiesSources: Meat, fish, poultry, cheese, nuts, milk, eggs, cereals, legumesRDI is about 0.8 g per kilogram of body weight
34Nutrients Vitamins Organic Essential nutrients that must come from foodsRDI varies for each vitaminSee table 25-4, 25-5 in the Anatomy bookExamples: A, B, C, K, Folic Acid
35Nutrients Minerals: Inorganic Essential for human metabolism Plants extract minerals from soil, we eat the plants, therefore we get the minerals.Most concentrated in teeth and bonesPlay vital role in nerve impulse conduction, muscle fiber contraction, blood coagulation (CA, NA, K, etc)Table 25-3 in Anatomy book for more infoExamples: Zinc, Iron, Sodium, Potassium, Calcium, Phosphorus
36MetabolismMetabolism - the series of processes by which food is converted into the energy and products needed to sustain lifeOn the cellular level, metabolism is the process of making ATP.Why is ATP so important?
37Metabolism ATP- Adenosine triphosphate: The version of energy useful to cellsATP ADP (triphosphate to diphosphate)- loss of the phosphate releases energyLost phos. recharges (like a battery) and bonds with an ADP to make an ATP: Energy must be available in the cells for this to occurCellular Respiration provides the energy to regenerate ATP, ATP provides the E for cellular activities.
39Metabolism Carbohydrate Pathways Carbohydrates are many sugars hooked together. These pathways break them into individual glucose moleculesCHO used as energy or converted to glycogen or fatGlucose molecules absorbed from sm. Intestine into blood stream and delivered to body cellsInsulin helps transfer glucose across the cell membrane3 Steps of Cellular Respiration = 1 Glycolysis, 2 Kreb’s Cycle, and 3 Electron Transport Chain (ETC) combined
40Metabolism Glycolysis: Process that breaks down the glucose into pyruvic acidOccurs in the cytoplasm (all cells)Product is pyruvic acid which is moved to the mitochondriaNet Yield 2 ATP
42Metabolism Kreb’s Cycle (Citric Acid Cycle): Occurs in membrane of the mitochondria, involves the pyruvic acid made in glycolysisHigh E compounds made (8 NADH and 2 FADH2) which donate electrons to the electron transport system (ETS)Net Yield 2 ATP
44Metabolism Electron Transport System: ATP produced when NADH and FADH2 release hydrogen atoms generating energyNet Yield around 32 ATP**Note: A total of 36 ATP are generated from the energy in 1 molecule of Glucose.**2 from glycolysis + 2 from Kreb’s cycle + 32 from ETS
47Digestive System Disorders Crohn’s Disease - is an autoimmune disease where the immune system attacks the gastrointestinal tract, producing inflammation.
48Heartburn (acid reflux) – when stomach juices regurgitate back into the esophagus through the cardiac sphincter. This causes a burning sensation that has nothing to do with your heart.
49Gallstones - form when bile stored in the gallbladder hardens into pieces of stone-like material. The largest gallstone on record was removed from an 80-year old woman in 1952 and weighed 6.29 kg (13.84 pounds).
50Digestive System Disorders Ulcers (peptic) – an erosion of the mucous or wall of the stomach or small intestine. Extremely painful because of the acidic wearing down of the walls of your GI tract.Hernia - is a protrusion ofa tissue or part of an organthrough the muscle tissueor the membrane by whichit is normally contained.
51Irritable bowel syndrome (IBS) - is a blanket term for a variety of diseases causing discomfort in the gastro-intestinal tract. It is also called spastic colon, characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits in the absence of any organic cause.
52Digestive System Disorders Cirrhosis – liver disease where the liver tissue is replaced by scar tissue. Typically caused by alcoholism or hepatitis.Jaundice - is a yellowish discoloration of the skin typically caused by excess bilirubin or the breakdown of red blood cells.
53Colon polyps - A colon polyp is a growth on the surface of the colon Colon polyps - A colon polyp is a growth on the surface of the colon. Some colon polyps are benign (not cancerous), but some are cancerous. Globally, cancer of the colon and rectum is the third leading cause of cancer in males and the fourth leading cause of cancer in females.
54Digestive System Disorders Lactose intolerance - the inability to digest significant amounts of lactose, the major sugar found in milk. Lactose intolerance is caused by a shortage of the enzyme lactase.Cystic Fibrosis – causes the blockage of the pancreatic duct due to the build up of hardened mucous.Hemorrhoids - are abnormally swollen veins in the rectum and anus.