DIGESTIVE SYSTEM FUNCTION

4 FUNCTIONS: 1. Physical breakdown of food into smaller pieces 2. Change food chemically by digestive juices into the end products of fat, carbs, and protein 3. Absorb nutrients into blood capillaries of the small intestine 4. Eliminate waste products of digestion

LOOK ON PG 392 FIGURE 18-15

DIGESTION TERMS Bolus Peristalsis Ptyalin Chyme Enzymes Soft, pliable ball of semi-digested food Peristalsis Wavelike motions that move food along esophagus, stomach and intestines Ptyalin In saliva in mouth, converts starches to simple sugar Chyme Food which has undergone gastric digestion Enzymes Help in digestion Chemical substances found in various digestive juices

DIGESTION in the STOMACH: Gastric juices released Stomach churns and mixes food and juice (chyme) Small amounts chyme enter duodenum Takes 2-4 hours for stomach to empty

DIGESTION in the SMALL INTESTINE: Digestion completed, absorption occurs Addition of enzymes from pancreas and liver (via gallbladder)

DIGESTION in the LARGE INTESTINE: Large quantities of water absorbed back into bloodstream Bacteria help break down undigested food Gas formation (flatulence) from bacterial action Feces Undigested semi-solid waste Defecation Colon and rectal muscles contract, external anal sphincter under conscious control

MOUTH (Figure 18-14 pg. 391) Food enters digestive system through mouth Broken down by teeth and mixed with saliva Inside mouth covered with mucous membrane Roof of mouth is hard palate Uvula Prevents food from going up nose when you swallow

TONGUE Attached to floor of mouth Helps in chewing and swallowing Made of skeletal muscle Taste buds on surface

SALIVARY GLANDS Three pairs Secrete saliva Parotid What are they? Parotid: secretes ptyalin salivary amylase onto inner cheeks Submandibular: secretes mucin and ptyalin at base of tongue Sublingual: secretes mucous (no ptyalin) and found on either sides of tongue Smallest of the three Secrete saliva Parotid Largest salivary glands, become inflamed during mumps

TEETH Gingiva – gums that support and protect teeth Mastication – chewing Deciduous – baby teeth How many? Adult teeth

STOMACH Cardiac sphincter Pyloric sphincter Rugae Circular layer of muscle Controls passage of food into stomach Pyloric sphincter Regulates entrance of food into duodenum Rugae Mucous coat lining Folds when stomach empty Muscular coat contracts (peristalsis) to push food into small intestine

SMALL INTESTINE Three sections: Absorption Read “Did you know?” What are they? Look on pg. 385 Absorption Digested food (nutrients) pass into bloodstream and on to body cells Undigestable passes on to large intestine Read “Did you know?”

SMALL INTESTINE continued END PRODUCTS OF DIGESTION: Carbohydrates are converted to simple sugars such as glucose Proteins are broken down into amino acids Fats are changed into fatty acids and glycerol

PANCREAS and GALLBLADDER Exocrine function – secretes digestive enzymes Also has endocrine function Gallbladder Stores bile When fatty foods digested, bile released by gallbladder

LIVER Manufactures bile Produces and stores glucose in the form of glycogen Detoxifies alcohol, drugs and other harmful substances Manufactures blood proteins Stores vitamin A, D and B complex

LARGE INTESTINE Water absorption Bacterial action Fecal formation Gas formation Defecation Look on pg. 393 and WRITE DOWN a few notes on each