Phases Include Digestion 1 Ingestionintake of food thru

• Phases Include Digestion 1. Ingestion-intake of food thru mouth 2. Mechanical digestion-chewing and mixing food 3. Chemical Digestion-breaks food down into building blocks/monomers 4. Secretion-release of H 2 O, acids, enzymes 5. Absorption-movement into blood stream of organics, water, electrolytes, vitamins 6. Elimination (defecation)-form and remove feces 7. Defense-high acidity, enzyme action, macrophages in lymph nodes 8. Peristalsis-involuntary, sequential contractions of smooth muscle. Move food through the tract

Digestion • Types – Mechanical (physical) • Chew • Tear • Grind • Mash • Mix – Chemical • Enzymatic reactions to improve digestion of – Carbohydrates – Proteins – Lipids

Salivary Glands • Produces saliva – Contains enzymes that break carbs into monomers • Parotid • Submandibular • sublingual 2/14/2022 4

Mouth • Teeth mechanically break down food into small pieces. Tongue mixes food with saliva (contains amylase, which helps break down starch). Forms bolus • Epiglottis is a flap-like structure at the back of the throat that closes over the trachea preventing food from entering it.

Digestive System Organization • Gastrointestinal (Gl) tract – Tube within a tube – Direct link/path between organs – Structures • • Mouth Pharynx Esophagus Stomach Small intestine Large Intestine Rectum 6

Esophagus • Approximately 10” long • Functions include: 1. Secrete mucus 2. Moves food/bolus from the throat to the stomach using muscle movement called peristalsis • If acid from the stomach gets in here that’s heartburn. 3. Lower esophageal (cardiac) sphincter relaxes and food enters the stomach.

Stomach • J-shaped muscular bag that stores the food you eat, breaks it down into tiny pieces. • Mixes food with digestive juices that contain enzymes to break down proteins and lipids. • Hydrochloric Acid in the stomach kills bacteria. • Food found in the stomach is called chyme. • Chyme spends 1 -3 hours in stomach small intestine 8

Small Intestine • Small intestines are roughly 7 meters long • Lining of intestine walls has finger-like projections called villi, to increase surface area. • The villi are covered in microvilli which further increases surface area for absorption. 9

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Small Intestine • Nutrients from the food pass into the bloodstream through the small intestine walls. • Absorbs: – 80% ingested water – Vitamins – Minerals – Carbohydrates – Proteins – Lipids • Secretes digestive enzymes 11

Small intestine • Divided into three sections – Duodenum • C-shaped • About 10 inches long • Stimulates the release of secretions from pancreas into duodenum. – alkaline; mostly H 20 and sodium bicarbonate » Neutralizes acid in chyme 2/14/2022 12

Jejunum and ileum • Jejunum – Absorption of digested food 2/14/2022 • Ileum – Bile salts and vitamin B 12 absorption 13

• Chyme remains in small intestine for 1 to 6 hours cecum (first part of large intestine • Appendix extends from the cecum – Bacteria and indigestible material sometimes gets trapped here appendicitis. 14

Large Intestine • About 5 feet long • Accepts what small intestines don’t absorb • Rectum (short term storage which holds feces before it is expelled).

• Functions Large Intestine – Bacterial digestion • Ferment carbohydrates • Protein breakdown Absorbs more water – Concentrate wastes –

Large intestine-Colon • Four divisions of large intestine – Ascending colon – Transverse colon – Descending colon – Sigmoid colon • Indigestible material remains here 12 - 36 hours rectum anal canal defecation 2/14/2022 17

Accessory Organs • Not part of the path of food, but play a critical role. • Include: Liver, gall bladder, and pancreas

Liver • Directly affects digestion by producing bile that is dumped into duodenum – Bile helps digest fat • filters out toxins and waste including drugs and alcohol 19

Gall Bladder • Stores bile from the liver, releases it into the small intestine. • Required for fat digestion so enzymes can digest fats into building blocks. • Fatty diets can cause gallstones

Pancreas • Produces digestive enzymes to digest fats, carbohydrates and proteins • Regulates blood sugar by producing insulin

Fun Facts • HOW LONG ARE YOUR INTESTINES? At least 25 feet in an adult. Be glad you're not a full-grown horse -- their coiled-up intestines are 89 feet long! • Food drying up and hanging out in the large intestine can last 18 hours to 2 days! • In your lifetime, your digestive system may handle about 50 tons!!

On a sheet of paper, write the name of each colored organ: • • Green: Red: Pink: Brown: Purple: Green: Yellow:

How’d you do? • • Green: Esophagus Red: Stomach Pink: Small Intestine Brown: Large Intestine Purple: Liver Green: Gall Bladder Yellow: Pancreas Great Job!

References and Links • Your Digestive System and How It Works – Digestive system diagram comes from this site • The Real Deal on the Digestive System • Pancreas: Introduction and Index • Your Gross and Cool Body - Digestive System