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 cecum-contains lymphatic organ called appendix Ascending colon

Large intestine Ascending colon Transverse colon-makes 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