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Digestive System Health Science 1 Ms. Marta Valdes, Instructor D’oh! Main Functions of the Digestive System •Ingest (take in food) •Digest (breaks down food, both mechanically & chemically) •Absorb (nutrient molecules) •Defecate (eliminates indigestible remains) Two Main Groups of Organs in Digestive System Alimentary Canal (“G.I. Tract”/ “The Tube”) Mouth Pharynx Esophagus Stomach Small intestine Large intestine Rectum Anus Accessory Digestive Organs (helps Tube with digestion) Salivary glands Teeth Tongue Gall bladder Pancreas Liver “The Tube” Accessory organs The Mouth • Physical digestion occurs here (mastication) • Salivary amylase (enzyme) starts carbohydrate digestion • Lyzosomes and IgA antibodies are produced here to inhibit bacterial growth • Swallowing pushes bolus down esophagus Food bolus Esophagus • Long tube that pushes food from mouth into stomach using peristalsis • Cardioesophageal valve allows food to go from esophagus into stomach Stomach • “C shaped organ”, approx. 10” long • Can hold 1 gallon of food • Folds in stomach (rugae) help with further mechanical digestion • Stomach secretes gastric juices which contain digestive enzymes (highly acidic HCl, pH=2) • Stomach itself is protected by a mucus layer • Food is broken down into a creamy, liquidy substance (chyme) • Protein digestion occurs here • Sphincter at bottom (pyloric sphincter) only allows small amounts of chyme to enter small intestine Small Intestine • Coiled muscular tube, that is 6-13 feet long • Chemical digestion of fats, proteins, and carbs occur here with help of specific enzymes released from accessory organs (pancreas & liver) • Absorption of small molecules (glucose, amino acids, etc.) occurs here through microvilli • Microvilli are tiny projections which increase surface area allowing for more absorption • Undigested waste leaves s. intestine via the ileocecal valve Small intestine Cross section microvilli Large Intestine • Reabsorption of water occurs here • Vitamin absorption occurs here • Undigested wastes collect & compact here (until expelled/excreted) • Sections of Large Intestine: Cecum, Ascending, Transverse, and Descending Colon, Rectum, Anus *Appendix (vestigial organ) sits at junction between the small and large intestine Accessory Digestive Organs •Salivary glands in mouth secrete saliva (essential for taste and forming bolus) & salivary amylase (which targets starch molecules and digests them into simple sugars) •Teeth carry out mechanical digestion of food •Tongue helps move food around in mouth to start digestion & helps form bolus and push it down esophagus Liver • • • • • • • • • • Largest gland in body, under diaphragm Humans have 4 lobes One of the most important organs in body Detoxifies blood Makes plasma proteins Destroys old red blood cells Maintains blood glucose Degrades hormones Produces cholesterol Produces urea from amino acids and sends it to kidneys • Produces bile Bile Bile is a yellow-green watery solution containing bile salts, bilirubin, cholesterol, and other substances. It is made in the liver but is stored in the gall bladder. It does not contain enzymes but the bile salts help to emulsify fat, breaking it down from large fat globules into smaller fat droplets which help with fat digestion in small intestine. Gall Bladder •Small, thin, green sac •Located near (inferior to) liver •Stores and concentrates bile •Release bile into small intestine for fat digestion through bile duct Gall stones Pancreas •Soft, long, pink (in body), triangular gland that extends horizontally in abdominal cavity •Produces enzymes that break down all categories of food (fats, proteins, and carbohydrates) •Also secretes an alkaline fluid to neutralize acidic chyme as it enters small intestine •Produces hormones such as insulin and glucagons Diseases & Conditions Associated with the Digestive System • Liver--------Cirrhosis Hepatitis • Rectum-----Hemorrhoids • Stomach----Ulcers • Large Intestine-------Constipation So altogether, the digestive system allows us to ingest and digest food so that we may obtain necessary nutrients and energy. Now, let’s review! The End!
