NUTR 1030 1st Edition Lecture 4 Outline of Last Lecture I. Define food insecurity and identify the factors that contribute to itII. Identify U.S. government programs designed to increase food securityIII. Describe organic food production, and discuss the current and potential uses of genetically modified foods, along with concerns related to safetyIV. Identify methods of food preservation and processing and describe the role of food additives in foodsV. Identify the major causes of foodborne illnesses in the U.S. and describe how consumerscan reduce the risk of these illnessesOutline of Current Lecture I. Understand the anatomy and physiology of the GI tractII. Understand the role of each organ during digestionIII. Identify important secretory substances that aid in digestionIV. Identify differences between Probiotics and PrebioticsCurrent LectureOrganization of the Human Body:Chemical Level: atoms combine to form moleculesCell Level: Molecules form organelles, use energyTissue Level: Similar cells make up tissues (connective, nervous, adipose, skeletal muscle, smooth muscle, etc.)Organ Level: Different tissues combine to form organsOrgan System Level: Organs make up an organ systemOrganism Level: Organ systems make up an organismThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Digestive System Overview:- Digestion- Process of breaking down foods into a form the body can use- Absorption- Uptake of nutrients from the GI tract into the blood or lymph- Excretion of waste matter- Immune system functionThe Structures of the Digestive Tract & the Digestive Process:Main Structures:- Oral cavity- Esophagus- Stomach- Small & Large intestinesAccessory Organs:- Pancreas- Liver- GallbladderAnatomy of the GI Tract:GI Tract (alimentary canal)- Long hollow muscular canalFour Layers:- Mucosa: innermost layer- hollow area is the lumen- Submucosa: contains blood vessels carrying nutrients- Muscle: move food forward- Serosa: outside layer- protects the tractSphincters- ring like muscles that control the flow of contents in the GI tractGI Motility: Mechanical Digestion, Mixing, and Propulsion:Mouth- Chews, breaks apart and mixes food with saliva. Tongue assists with movement in mouthPeristalsis- Wavelike muscular contractions that propel material along the esophagus, stomach and intestineSegmentation- Back and forth movement- breaks apart food in the stomach and intestines. This churning is produced by the three layers of muscleMass Movements- Peristalsis over widespread area to help eliminate waste. Moves material from one portion to another in large intestine, and eventually to the rectumEliminationVomitingImportant Secretions of the Digestive System:Secretion Site of Production FunctionSaliva Mouth Contributes to starch digestion, lubrication & swallowingMucus Mouth, stomach, small/large intestinesProtects GI tract cells, lubricates digesting foodEnzymes (amylases, lipases, proteases)Mouth, stomach, small intestine, pancreasPromotes digestion of carbs, fats and proteins into forms small enough for absorptionAcid (HCl) Stomach Promotes digestion of protein,destroys microorganisms, increases solubility of mineralsBile Liver (stored in gallbladder) Aids in fat digestion (emulsifies fat)Bicarbonate Pancreas, small intestine Neutralizes stomach acid when it reaches small intestineHormones Stomach, small intestine Regulates digestion & absorptionDigestion and the Mouth:Mastication (chewing)Saliva contains:- Enzymes- help break down starch to simple sugars- Mucus- lubricates food for easier swallowing- Lysozymes- kill bacteriaTongue has:- Taste receptors- Enzymes to break down fatty acidsTaste and smell- mouth and nose play roles hereBolus is formed and swallowedEpiglottis- barrier for blocking food from entering airwaySwallowing Process:Digestion and the Stomach:Stomach= Mixing tank- Food held here for 2-4 hours- Esophageal & pyloric sphincters prevent back flow and moving forward prematurelyStomach Secretions:Mucus-- Coats/lubricates food- Provides protective lining for stomach, prevents it from being digested- Depends on prostaglandins for releaseIntrinsic factor (for B12 absorption)Digestive secretionsFood mixed with stomach secretions- CHYMERoles of Stomach Secretions:Enzymes (by chief cells)- Pepsinogen (Pepsin is active form, enzyme that digests proteins)- Gastric Lipase- aids in fat digestion (minor contribution)Hydrochloric Acid (HCl) (by parietal cells)- Inactivates proteins- Protects us from pathogens (destroys them)- Dissolves bonds that hold minerals in foods- Activates pepsinogen, turns it into pepsinSmall Intestine:Most digestion and absorption occurs here- 95% of absorption takes place here- Food remains here for 3-10 hoursKey Structural features:Sections- duodenum, jejunum, ileumVilli- finger-like projections lined with cells- Microvilli form brush borderFunctions of the folds & Villi:- Increases surface area for digestion and absorption- Walls are folded, have VilliVilli contain:- Goblet cells- make mucus- Endocrine cells- hormones- Enterocytes- absorptive cellsProduce digestive enzymes, produced in crypts & migrate to villi tipsMicrovilli- hair-like extensions of the cells’ membranes, called a brush borderLiver, Gallbladder & Pancreas (accessory organs):Liver produces Bile- Bile acids aid in digestion- Enterohepatic circulation (recycling)Gallbladder stores Bile- Releases it into the small intestine upon stimulationPancreas produces and releases:- Sodium bicarbonate to raise the pH in the SI- Lipases, proteases and pancreatic amylase to aid in SI digestion- Hormones insulin/glucagonHormones also produced in the SI to regulate digestionLarge Intestine:Parts of the large intestine-- Colon, comprised of 5 sections(cecum, ascending colon, transverse colon, descending colon and sigmoid colon)- Rectum - AnusLittle Digestion and overall absorption occurs here- Some un-digestible food fiber is partially digested by the bacteria living in the large intestine. Most fiber is not absorbed and passes out of the colon as wasteRoles of Large Intestine- Absorption of water (90% remaining) and electrolytes, some vitamins- Formation and elimination of feces (defecation)Bacterial Flora:Beneficial bacterial flora- Controls pathogenic bacteria- Synthesize Vitamin K and Biotin- Aid lactose digestion and fermentationPro-biotic- Live bacteriaPre-biotic- Non digestible carbohydrates that