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The DIGESTIVE System Digestion defined Breakdown of food into useable nutrients Two kinds Mechanical Chemical Chemical Vs Mechanical Digestion Chemical: Enzymes break down for absorption--ENZYMES Mechanical: broken down into smaller parts--MASTICATION AND MACERATION Alimentary canal Tube food passes through Begins at mouth ends with anus Food is chewed Bolus created Bolus swallowed Pharynx Bolus moves into pharynx fancy word for throat has three parts – Nasopharynx – Oropharynx – Laryngopharynx Esophagus 8-12 inches long Smooth muscle contractions called: Peristalsis-rhythmic Cardiac (aka Gastroesophageal) sphincter Has no mucous membrane to protect from Hcl from stomach Stomach J-shaped 3 sets of muscle in different directions Hcl= chemical breakdown Pepsin begins protein disgestion Contain rugae to increase surface area Change bolus into chyme Mucus protects stomach lining Small intestine 3 parts Duodenum--most chemical digestion takes place here Jejunum-absorption continues Ileum absorption continues 15-22 ft long Absorbs some of the water in food & what you drink Villi Nutrients are absorbed through structures called villi Large intestine called the colon Main function water absorption + Vit K absorption Begins with cecumcontains lymphatic organ called appendix Ascending colon Large intestine Ascending colon Transverse colonmakes hunger sounds Descending colon Sigmoid colon Rectum Anal canal Anus Accessory organs CONTRIBUTE to digestion process NOT part of the canal or tube Food DOES NOT pass through them Tongue and teeth Teeth break food down into smaller pieces Tongue moves food to the back of throat Parts of a tooth Crown = exposed portion above gum line Neck = between crown & root Gingivae-gums Root = one to three- embedded in mandible & maxillae Parts of a tooth Enamel = outermost part, protects from wear & tear – the hardest substance in the body Dentin = calcified connective tissue Gives tooth it’s basic shape & rigidity Parts of a tooth Pulp Cavity = large cavity enclosed by dentin--filled with pulp Cementum = a bone-like substance covers--dentin of roots Parts of a tooth Periodontal Ligament an area of dense fibrous connective tissue anchors teeth in position serves as a shock absorber when chewing Salivary glands Saliva is: Mostly water Enzymes that digest carbs—Amylase— breaks starch into maltose Soften and moisten food Salivary glands 6 total--3 pair Parotid, submandibular, and sublingual Liver and Gall Bladder Liver makes bile Bile is stored in gall bladder (sac) Bile breaks down fats--emulsification Secreted as it is needed Eliminated through intestines Pancreas Located posterior to stomach Secretes enzymes to chemically breakdown fats, carbs, and proteins Increases pH of chyme Pancreatic juice—thru pancreatic duct—thru heptopancreatic sphincter Mastication Chewing--makes bolus Teeth mechanically break down food Food is mixed with saliva Deglutition Swallowing Tongue pushes food to back of throat Oropharynx--second part of throat Smooth Muscles contract causing peristalsis Voluntary Peristalsis General term for wave-like contractions in esophagus and intestines Rhythmic smooth muscle contractions Maceration Stomach contracts and Bolus mixed with gastric juices and Hcl until it is liquid-like Bolus is changed to chyme Empties through pyloric sphincter Segmental contraction Each segment of small intestine contracts Helps mix bile and pancreatic juices with chyme Smooth Muscle contractions peristalsis in each segment Absorption Nutrients absorbed in jejunum and illeum Some nutrients & water absorbed thru stomach Some water absorbed through small intestine Most water absorbed through large intestine Haustral churning Each segment in large intestine is called a haustra Smooth muscle contractions move contents along (type of peristalsis) Water is absorbed in large intestine Defecation Elimination of material that is undigestible Plant fiber-necessary for health of the intestines Formation of feces and elimination of feces Nutrients are broken down in different places in digestive system Carbohydrates Begin digestion in mouth with enzyme AMYLASE from salivary glands Amylase breakdown continues in stomach Finish breakdown in duodenum (pancreatic juice) Fats Fats begin mixing with gastric juices in stomach Bile from gall bladder goes into small intestine to break them down Pancreas secretes enzymes (lipase) to finish chemical breakdown Proteins Begin mixing with pepsin in stomach Finish with secretions from pancreas into duodenum Digestion system End