Chapter 11 The Digestive System - PowerPoint Presentation

1. Chapter 11The Digestive System

2. The Digestive System and HomeostasisThe human body is a complex structure that relies on the working together of a variety of specialized cells and organ systemsThe cells and tissues require a variety of different nutrients to perform their vital functions. If these functions are not carried out, homeostasis may be lost, ex: not enough glucose for cellular respiration, NO ATP/ Energy!Sometimes different types of cells require different nutrientsNutrients are the substances which are used by the body to grow, repair cells and maintain cells, and regulate bodily functions.See chapter 1-3 notesNutrients are not created by our bodies, they must be brought into the body and be changed to be usable.ALL foods contain nutrients and must be taken in by animals to be used for vital processes

3. The Purpose of Digestion Animals can eat food to bring nutrients into the body, however, the nutrients in this food are often contained within large, complex organic compoundsThese compounds must be broken up into smaller units to be used by the bodyDigestion is the process by which these large compounds are broken into smaller, simpler units which can be absorbed and used by the cells of the body.

4. The 6 Essential NutrientsThe following 6 types of nutrients are incredibly important to the functioning of body systems and are required to maintain homeostasis:1). Carbohydrates: (C-H-O)Sources: Plants, Fruits, Vegetables, Breads, Pastas, Functions: The major source of energy for the bodyBreakdown of carbs creates glucose which is used by all cells to make ATP= needed for vital processes2). Lipids (Fats):Sources: Animal and Plant Fats. Carbohydrates sometimes converted to lipids. (Ex: Butter, Margarine, Meats, etc)Functions: Energy Storage, Protection for Organs, Component of Cell Membrane (Lipid Bilayer), Carries Vitamins

5. The 6 Essential Nutrients (cont’d)3). ProteinsSources: Eggs, Milk, Cheese, Meats, Fish, Poultry, Legumes, NutsFunctions:Proteins are large macromolecules made up of amino acids which can be responsible for various bodily functions. (Ex: cell maintenance and repair, DNA replication, etc)Plant and animal proteins are broken down by digestion and the resulting amino acids can be used in building blocks for the construction of human proteinsProtein makes up a large part of the hair, nails, nerves, skin, and muscles. (Keratin in hair, nails) (Collagen in skin)Enzymes (catalyse chemical reactions in body) and antibodies are specialized proteins

6. The 6 Essential Nutrients (Cont’d)4). VitaminsSources: Different foods contain different vitaminsSee Pg. 358 Table 11.1 in Text Know these vitamins, their functions, and sources: Vitamins A, D, K, and EFunctions: Involved in various metabolic activities depending on the vitaminInvolved in enzymatic activity (I.E speeding up chemical reactions)Some vitamins are fat soluble, they are stored in the body’s fat to be used when needed. (Vitamins A, D, E, and K are fat soluble- know these)Water soluble vitamins are lost through urination, they must be replenished daily.

7. The 6 Essential Nutrient (Cont’d)5). MineralsSources:Different foods contain different mineralsEx: Salt contains sodium, bananas contain potassium, milk and cheese contain calcium, and many cereals and wheat products contain iron.Functions:Various functions depending on the mineralIron is used to make up hemoglobin in blood cellsCalcium is used to strengthen bonesSodium and Potassium important in nerve functioning

8. The 6 Essential Nutrients (Cont’d)6). WaterSources: Various Foods ( Ex: Fruits) and Liquid Water (and other drinks)Functions:Mainly used as a solvent (dissolves things) but also important for cell structure, temperature regulation, protection of joints and organs, etc. Carbohydrates, Lipids, and Proteins are macromolecules and must be broken down by digestion to be usedVitamins, Minerals, and Water require no digestion at all to be used

9. The Two Types of DigestionThere are two types of digestion which both play a major role in the digestive process which food undergoes.1). Mechanical Digestion- Mechanical digestion is the breaking down of foods through physical processes. Includes the actions of chewing, shearing, and grinding food with teeth. This makes the food smallerThe tongue manipulates the food into a mass called a bolusWave-like contractions in the esophagus help to break up the food even more. (Peristalsis)Churning of stomach muscles helps to better mix the food with stomach acids.

10. The Two Types of Digestion2). Chemical Digestion- Chemical Digestion is the breaking down of foods and nutrients into their molecular components by chemicals including stomach acid and digestive enzymes.Chemical digestion begins in the mouth, salivary amylase, an enzyme in saliva, breaks down sugars into simpler componentsMajority happens in the stomach where hydrochloric acid is secreted to break down foods into a mixture called chymeAlso occurs in the small intestines where digestive enzymes further break down food, enzymes come from various places such as the liver and pancreas

11. Food’s Journey Through The Digestive TractThe digestive process begins in the mouthThe mouth is equipped with teeth lining the upper and lower jaws, some teeth are specialized for breaking down different types of food (mechanical)Three sets of salivary glands in the mouth produce saliva which moistens the food and makes it easier to swallow (mechanical).The Mucin found in the saliva makes the food slippery and helps to form the bolusThe production of saliva is increased by hunger and the scent and taste of food (literal mouth watering)Salivary Amylase in saliva breaks down the sugars (chemical)The tongue is covered in papillae which contain the taste budsUvula prevents the food from travelling upward into the pharynx when swallowed

12. The PharynxThe pharynx refers to the cavity behind the nose and mouth which connect them to the esophagus and trachea1). Trachea- the tube to the lungs, covered by the glottis and epiglottis to keep food from entering the lungs2). Esophagus- a muscular tube connecting the mouth to the stomach Muscles in the esophagus automatically contract, pushing food down the tract and breaking it up furtherThis is called peristalsis (Mechanical digestion)Chemical digestion does not occur here

13. The EsophagusA tube, about 30cm long, made up of longitudinal (up and down) and circular muscles that connects to the stomachThese muscles contract, causing peristalsis to occur, pushing the bolus through the tube

14. StomachThe stomach is a J-shaped organ in the abdominal cavity, the esophagus empties into the stomachTwo sphincters are present in the stomach, one at the top/entrance and one at the bottom/exitThe Cardiac Sphincter- is a muscle between the esophagus and the stomach, it opens to allow food into the stomach and closes to keep stomach acid from burning the esophagusThe Pyloric Sphincter- Muscle between the small intestine and stomach. It regulates when digested food (chyme) moves into the intestinesRugae- the folds in the stomach lining, increase surface area for digestion

15. Digestion in the StomachWhen food enters the stomach, the stomach’s wall contract to mix and churn the food with gastric juices (peristalsis is happening here too)This mixing action is considered to be mechanical digestionFood can remain in the stomach between 2-6 hours. The stomach digests food more slowly when sleeping so it can take even longer in this caseTotal capacity of the stomach is 2L of food or liquidsGastric Glands and Pyloric Glands release gastric juices which work to break down food and nutrients into smaller, molecular compounds (chemical)Production of gastric juices is stimulated by: thought, smell, or sight of food, food entering the stomach, or the stretching of the stomach wall (read)With a pH of about 2 (extremely acidic), the gastric juices are able to break down food and digest complex molecules like proteins

16. Digestive System pH

17. Gastric Juices- ContentsThe Gastric Juices secreted in the stomach contain various important components1). Hydrochloric acid (HCl)Responsible for lowering stomach pH to 2 or below, necessary for the digestion of proteinsActivates the enzyme pepsinKills bacteriaBreaks down celluloseIs not responsible for the bulk of the digestive action which occurs in the stomach

18. Gastric Juices- Contents2). Pepsinogen (inactive protein)Pepsinogen is activated by HCl and becomes pepsin (an active enzyme)Pepsin is responsible for breaking down proteins into polypeptides which are chunks of protein3). Water4). Gastrin- the hormone which controls the release of gastric juices5). Protective mucus which keeps the acid in the stomach from burning through the stomach lining

19. Amino Acids and Polypeptides(READ ONLY)

20. Seatwork/HomeworkPg. 373 #1,2,4,7

21. Small IntestineFollowing the digestion which occurred in the stomach, the chyme then enters the small intestine by way of the pyloric sphincterThe small intestine is a tube between the stomach and the large intestine which is about 2.5cm in diameter and about 7m in length. Fun Fact: The small intestine is actually longer than the large intestine by about 5.5m The small intestine is divided into three partsDuodenum- The first 25cm after the stomachJejunum- the next 2m of intestine after the DuodenumIleum- the last 5m of small intestine (makes up most of SA)Digestion concludes in the small intestine, the final steps of the digestion (breaking down) occur hereAll nutrients should be absorbed into the body here

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23. Digestion in the Small Intestine1). Mechanical (2 Processes in SI)Peristalsis- contraction of the muscles of the small intestine works to push the digested food along its path through the SI and further mixes itEmulsification- fats are emulsified in the small intestine by Bile produced by the liver and stored by the gall bladderEmulsification means the fat is broken down into tiny droplets, increasing the surface area for absorption Bile enters the duodenum through the common bile duct which connects the liver and gall bladder to the duodenumBile also activates Lipases in the SI, lipases are enzymes which break down fatsBile itself is NOT an enzyme

24. Digestion in the Small Intestine2). Chemical DigestionThere are two important glands involved in chemical digestion in the small intestine: A). Pancreas glandsB). Intestinal glands

25. A). PancreasThe pancreas is an organ of the body which also acts as an enzyme producing glandThe pancreas is located just outside of the small intestine and is attached to the abdominal wallThe pancreas produces pancreatic juices that enter the duodenum of the small intestine through the pancreatic duct and common bile ductThe pancreatic juices contain:1) Pancreatic Amylase- an enzyme which breaks starch down into maltose2) Lipase- an enzyme which breaks fats down into “fatty acids” and “glycerol” 3) Proteases/Trypsin- enzymes the convert polypeptides (from proteins broken down in the stomach) into smaller polypeptides4) Sodium Bicarbonate- raises pH in the small intestine to 8 (basic). This neutralizes the acidic chyme from the stomach

26. B). Intestinal GlandsFound in the walls of the small intestineThese glands produce intestinal juices containing:1) Peptidases- break down the polypeptides in the small intestine into individual amino acids2) Lipases- convert fats to “fatty acids” and “glycerol” (same as in pancreatic juices)3) A group of enzymes which break disaccharides (two sugars joined together) into glucose:A) Maltase- Breaks maltose into glucoseB) Sucrase- Breaks sucrose into glucoseC) Lactase- Breaks lactose into glucose

27. B. Jejunum Function:Finish breakdown of carbohydrates and proteins so they can be absorbed by the villi.A. Duodenum - Function:Absorb nutrients.Push remaining undigested materials into the large intestine.C. IleumChyme is immediately mixed with Bile from the liver/gallbladder and pancreatic juices and bicarbonate ions from the pancreasDigestion Overview

28. Pancreatic Amylase

29. The Large IntestineCecum: beginning of large intestineColon: 3 sections, ascending (up), transverse (across), and descending (down)Rectum: Where waste is stored until expulsion

30. The Large IntestineDigestion was completed in the small intestineRemember that this refers to breaking foods and nutrients down into smaller unitsAs such, no real breaking down occurs in the large intestineStructure: The large intestine is a 1.5m long tube between the small intestine and the anus. It has a larger diameter than the small intestine and is made up of the caecum, colon, rectum, and anal canalThe function of the large intestine is to absorb any leftover nutrients (mainly vitamins) as well as any remaining water and salts in the waste productsAlso produces an alkaline mucus to neutralize acids and lubricate feces (waste)

31. Absorption in the IntestinesBecause the small intestine is specialized for absorption of nutrients, and the large intestine isn’t, the small intestine contains structures called villi which increase the surface area for absorption in the small intestineThere are no villi in the large intestineVilli are small, finger-like projections on the inner walls of the small intestine. Each villus (singular) contains a network of capillaries to allow nutrients to diffuse into the blood stream ( all villus capillaries lead back to liver where absorbed glucose is stored)Each villus is also covered in microvilli, even smaller projections which further increase surface area.Without villi, the small intestine would have to be 70m long to absorb the same amount of nutrients!If the nutrients were not absorbed here, they would be expelled from the body, homeostasis would be affected as tissues may starve for essential nutrients

32. Structure of the Villi

33. From Colon to AnusWater and dissolved minerals from the digested foods are absorbed into the blood stream in the colonBacteria in the gut release more nutrients through their own interaction with digested foodIndigestible remains (feces) are left behindThe feces is pushed through the rest of the large intestine, into the rectum, and anal canalAn anal sphincter sends a message to the brain when waste is ready to be expelled, and the brain responds and the sphincter opens and feces move out the anusThis allows some limited control over bowel movements

34. Important Chemical Digestion DefinitionHydrolysis: the chemical breakdown of food by waterHydro= water Lysis= breakHydrolysis is used at certain points throughout the digestive process, however it is very slow.Three groups of enzymes speed up the process of hydrolysisLipases- break down fatsCarbohydrases- break down sugars (ex: salivary amylase)Proteases- break down proteins (ex: pepsin)

35. Enzyme ActivityEnzyme activity is impacted by:1) Temperature (heat speeds it up/ cold slows it down)2) Concentration (more=faster / less= slower)3)pH (variable but usually neutral or basic)Pg 387- 4,6,7,8,9

36. Digestive Disorders- UlcersThe stomach is lined with protective mucus that is created with the gastric juicesPyloric Glands- produce the protective mucus which prevents the stomach from digesting itselfAn ulcer is the erosion of the protective mucus in an area of the stomach, as a result, the gastric acids burn the lining of the stomach creating soresThe main cause of ulcers are bacteria which stop mucus productionCan also be caused by: stress, smoking, alcohol consumption, highly acidic diet (ex: case of Pepsi a day)

37. Digestive Disorders- UlcersWhen the cause is bacteria, the site of bacterial attachment is where mucus production stops and ulcers formTreatment: Medication to inhibit stomach acid productionAntibiotics to kill bacteriaLifestyle changes (ex: quit smoking, diet)Surgery (serious cases)http://www.youtube.com/watch?v=9-aVA8mz4e4http://www.youtube.com/watch?v=SWMWsOXlBwE