The Digestive System!

What molecule does our body break down for energy?Where do we get this molecule?Recall from Biology Lab, what do Iodine and Benedicts solution test for?Explain the reactions of these two indicators.

DO NOW:Digestive Enzymes Pre-LabObjectivesTo use your knowledge of indicators and macromolecules to determine the effects of digestive enzymes.To explain how digestion begins in the mouth.Do NowWhat do we already know about the digestive system? List 3 things! What would happen if you were tied upside down, would you still be able to eat? Explain.The Digestive System!Chapter 15

ObjectivesTo compare and contrast chemical vs. mechanical digestion.To explain the general characteristics of the alimentary canal.To explain the process of swallowing and peristalsis.To identify the structures of the mouth and explain their function.To understand the necessity of salivary glands and name each type.DigestionChemical digestion- complex molecules are broken down into smaller moleculesMechanical digestion- physical movement of food that breaks it down into smaller piecesEx. Chewing, grinding, mashingChewing is called mastication

6Components of Digestive SystemAlimentary Canaldigestive tractMouth, pharynx, esophagus, stomach, small intestine, large intestine, and anal canalAccessory Structures: Salivary glands, liver, gallbladder, & pancreas

Alimentary CanalMuscular tube that passes through the bodys ventral cavity9 meters longContains 4 layers

8Alimentary CanalMucosa:Protects the tissues beneath it & carries out secretion and absorptionConsists of epithelium, underlying CT, and a little bit of muscle.

2) Submucosa:Nourishes surrounding tissue and carries away absorbed materialsConsists of loose connective tissue, blood vessels, glands.9Alimentary Canal3) Muscular Layer:Layer which moves the tubeContains: Two coats of smooth muscle tissue & nerves (plexus)Fibers of the inner coat surround the tube When they contract the tubes diameter decreasesFibers on the outer muscular coat run lengthwiseWhen they contract the tube shortens

4) Serosa:Protects underlying tissues and secrete serous fluid10Alimentary Canal

11Movements of theAlimentary CanalMixing MovementOccurs when smooth muscle in small units of the tube contract rhythmicallyMixes food with digestive juices secreted by the mucosa

Propelling MovementKnown as peristalsis

12Organs of the Digestive SystemThe MouthReceives food and begins digestion mechanicallyReduces the size of solid particles and mixes them with saliva Oral cavity - Lips, cheeks, tongue & palateVestibule - Narrow space between teeth, cheeks, & lips

13Salivary GlandsSecrete salivaContain 2 cellsSerous cells: produce amylase (breaks down carbs)Mucus cells: produce mucus to bind to food and lubricate during swallowing.

14PharynxConnects nasal and oral cavitiesContains 3 partsNasopharynxOropharynxLaryngopharynx (passageway to the esophagus)

15Swallowing MechanismFood is chewed and mixed with saliva,tongue rolls this into a mass or bolus and forces it into the pharynxFood stimulates sensory receptors around the pharyngeal opening triggering the swallowing reflex.Momentarily inhibits breathing, peristalsis transports food into the esophagus and to the stomach. 16Do Now1) Read the story about William Beaumont and his work with St. Martin in the early 1800s.3) Write a short summary of what you read.17ObjectivesExplain the functions of the esophagus, stomach, small intestines, and large intestines in digestion.Identify different enzymes located in the digestive system and explain their function.Understand different conditions caused by improper functioning of the digestive system.18Swallowing Mechanism

19EsophagusAbout 25 cm longConnects pharynx to the stomachSeparated from the stomach by the cardiac sphincter.Contracts and closes the sphincter to prevent regurgitation.

20Heartburn! Regurgitation of stomach acid into the esophagus.

21StomachJ shaped with about a 1 liter capacity.Contains rugae which allow it to expandDivided into 4 regionsCardiacFundicBodyPyloric

22Cup your hands..

Thats approximately the size of the stomach & can hold about 1 LiterTrivia23Stomach

24Stomach UlcersBreaking down of the mucosal lining.

25Stomach JuicesGastric Juice consists ofHClMucusViscous alkaline secretion that coats the stomachEnzymesProteases such as Pepsin- digests protein (starts as pepsinogen and when mixed with HCl makes pepsin)Intrinsic factor which helps the small intestine absorb B12

26Stomach JuicesThe mixture of gastric juice and the bolus gives us chyme. Stomach contractions push chyme a little at a time into the sm. Intestine.Type of food can effect rate of emptyingFatty food = 3-6 hrs. in stomachProteins move more quicklyCarbs go through the fastest!

27Gastric AbsorbtionThe stomach mostly breaks things downCan absorb only small amounts of water, certain salts, alcohol, and some lipid-soluble drugs.EX: Aspirin

28PancreasSecretes pancreatic juice into the duodenum (1st part of sm. Intestine)Pancreatic enzymes:Pancreatic amylaseDigests carbsPancreatic lipaseDigests fatsNucleasesDigests nucleic acidsProteases: trypsin, chymotrypsin & carboxypeptidaseDigest protein

29LiverEffects carbohydrate, lipid, and protein metabolism.Produces bile Contains bile salts, bile pigments (bilirubin and biliverdin)**bile salts emulsify fats (turn them into little globs instead of big globs!) and also increase absorption of fat-soluble vitamins (A,D,E, & K)

30ReviewWhat is the process that occurs after swallowing?What is the scientific name for the digestive tract?How many layers is this tract?What are the 3 parts of the pharynx?What is absorbed in the stomach?What does the pancreas do?Why are bile salts important?