DIGESTION

Digestion Mechanical and chemical breakdown of foods... Absorption of resulting nutrients by cells ALIMENTARY CANAL: tube extending 9 meters from the mouth to the anus Mucosa—Submucosa—Muscular layer- -Serosa LUMEN: space within the intestines

Organs ALIMENTARY CANAL ACCESSORY ORGANS Salivary Mouth Glands Pharynx Esophagus Stomach Small Intestine Large Intestine Anal Canal (rectum & anus) Salivary Glands Liver Gallbladder Pancreas

Mouth Digestion begins here Mechanical & chemical (starches: amylase) Lips, teeth, cheek, tongue, salivary glands, papillae, palate, frenulum, tonsils, vestibule, tongue

DIAGRAM OF MOUTH

Tongue Function: Mix food particles with saliva during chewing and move food toward the pharynx during swallowing PAPILLAE: bumps on tongue; taste buds FRENULUM: flap that anchors tongue to bottom of oral cavity

Salivary Glands Moisten food; secret amylase to begin starch digestion 3 pairs of major salivary glands PAROTID glands - largest of the major glands - secretes a clear, watery fluid rich in amylase SUBMANDIBULAR glands - predominantly serous secretion w/ few mucous cells SUBLINGUAL glands - smallest of the major glands - secretion primarily mucous type

DIAGRAM OF SALIVARY GLANDS

Teeth Function: Break pieces of food into smaller pieces BOLUS: moist ball of food INCISORS: (8) chisel-shaped with sharp edges to bite off larges pieces of food CUSPIDS: (4) “canine” teeth; sharp BICUSPIDS: (8) tear & grind MOLARS: (12) flattened surface to grind food particles <Wisdom Teeth> 3rd set of molars; late teens; early 20’s

Parts of Teeth CROWN: projects beyond the gum ROOT: anchored to the alveolar process of the jaw ENAMEL: covers the crown DENTIN: bulk of the tooth below enamel PULP: combination of blood vessels, nerves, and connective tissue (blood vessels and nerves reach pulp cavity through ROOT CANAL) GINGIVA: gum

TEETH

TOOTH

Pharynx Connects the nasal & oral cavities with the larynx & esophagus “back of throat” 3 parts nasopharynx: communicates with the nasal cavity & provides a passageway for air during breathing oropharynx: passageway for food moving downward from the mouth and for air laryngopharynx: passageway to the esophagus

TONSILS Produce antibodies to fight infection TYPES LINGUAL PALATINE PHARYNGEAL

Uvula Cone-shaped projection Function: drawn upward during swallowing to close the opening between the nasal cavity & the pharynx

Esophagus passageway from the pharynx to the stomach “food tube” 25 cm long PERISTALSIS: muscular contractions that move food No digestion occurs here EPIGLOTTIS: flap that closes trachea when we swallow to prevent food/liquid from entering the trachea LOWER ESOPHAGEAL SPHINCTER: prevents food from backing up into esophagus

Stomach J-shaped pouch Just below diaphragm 1 L capacity or more! RUGAE: folds 4 regions: cardiac, fundic, body, and pyloric CHYME: semifluid paste of food Chemical digestion of proteins Gastric juice: HCl & pepsin…highly acidic (pH 2) PYLORIC SPHINCTER - valve that controls food backing up in the stomach

FUNCTIONS OF THE STOMACH Begins mixing process with gastric juice Begins protein digestion Moves food to small intestine Limited absorption

THE STOMACH

Gastric Secretions Gastric glands contain 3 types of secretory cells: mucous cells, chief cells, & parietal cells = gastric juices Mucous cells secrete mucus to prevent stomach from digesting itself! Chief cells secrete digestive enzymes Parietal cells releases hydrochloric acid Pepsin: digestive enzyme in gastric juice Pepsin w/ HCl begins the digestion of nearly all proteins into polypeptide strands Gastrin: hormone that regulates gastric secretions

Small Intestine Most important organ of digestion 6 m if stretched out! Most absorption takes place here Many folds (intestinal villi)– increase the surface area for easier absorption 3 regions: DUODENUM; JEJUNUM; ILEUM

Portions of Small Intestine Duodenum C shaped Receives chyme from stomach Receives pancreatic juice & bile Several enzymes released to complete digestion of proteins, dipeptides, disaccharides, fats Jejunum Absorption of digested nutrients Ileum

More about the Small Intestine MESENTARY: tissue that suspends the jejunum & ileum from the abdominal wall Lacteal: lymphatic capillary found in the intestinal villi FUNCTIONS: Receive secretions from pancreas & liver Completes digestion Absorbs products of digestion

Large Intestine Shaped like an upside down U 1.5 m long No villi Absorbs water & electrolytes Forms FECES (75% water; undigested material; bacteria; electrolytes ILEOCECAL SPHINCTER: b/w ileum of small intestine & cecum of large intestine

Regions of Large Intestine CECUM ASCENDING COLON TRANSVERSE COLON DESCENDING COLON SIGMOID COLON

Other Info to Know about the Large Intestine APPENDIX: lymphatic tissue between small & large intestine HEMORRHOIDS: “pain in the rear”…enlarged/inflammed rectal veins…itching, burning, bleeding MUCUS produced in colon serves 2 functions: Binds fecal matter Protects intestinal wall against abrasive action of undigested waste LARGE INTESTINE VS. SMALL INTESTINE: larger diameter NO VILLI

Rectum & Anus Feces stored in the rectum ANAL CANAL: passageway through which feces passes as it passes out the body through the anus DEFECATION: removal of feces INTERNAL & EXTERNAL ANAL SPHINCTERS control the release of feces

ACCESSORY ORGANS

Liver Heaviest organ is body (3 pounds) Well-supplied with blood vessels Right & left lobes *blood sugar maintenance *lipid metabolism (bile secretion) Produce BILE *emulsification of fats *protein metabolism (most important function) *stores glycogen, iron, vitamins A, B12, D *removes toxic substances such as alcohol (detoxification)

Gallbladder Stores bile & releases bile to duodenum Released through COMMON BILE DUCT Cholesterol in bile can form crystals (GALLSTONES)

Pancreas Secretes pancreatic juice Enzymes that digest carbohydrates (amylase), fats (lipases), proteins (trypsin…), & nucleic acids (nucleases) Neutralizes stomach acid Produces insulin Pancreatic duct: connects with duodenum