Digestion System Ms. Day/ AP Biology

Nutrition There are two parts to Nutrition: Ingestion Digestion process of taking food into the digestive system so that it may be broken down Digestion the breakdown of food (either chemically or mechanically) in order to use its nutrients

Types of Nutrients Micronutrients- vitamins, minerals, & water Macronutrients- proteins, lipids, carbohydrates, etc…

Types of Nutrients (Macromolecules) Carbohydrates sugars for energy and carbon skeleton structure (carbon chains) Fats broken down into fatty acids and glycerol phospholipids for cellular membrane Proteins amino acids for protein synthesis Nucleic Acids Nucleotides for RNA and DNA synthesis

Other Types of Nutrients Vitamins usually work with enzymes  water soluble (excess excreted) and fat soluble vitamins (excess stored) Minerals inorganic substance- ex: calcium Water helps regulate body temp act as a solvent (hydrolysis)

Human digestive system After chewing and swallowing, it takes 5 to 10 seconds for food to pass down the esophagus to the stomach, where it spends 2 to 6 hours being partially digested. Final digestion and nutrient absorption occur in the small intestine over a period of 5 to 6 hours. In 12 to 24 hours, any undigested material passes through the large intestine, and feces are expelled through the anus.

Introduction to Digestive System Used for breaking down food into nutrients Nutrients then pass into the circulatory system and are taken to where they are needed in the body

There are 4 stages to food processing: Ingestion: taking in food Digestion: breaking down food into nutrients Absorption: taking in nutrients by cells Excretion: removing any leftover wastes

Step #1: The Mouth Food enters mouth MAIN FUNCTION: Food is physically broken down by the teeth Mechanical digestion Then food is chemically broken down by amylase Amylase = enzyme (helper molecule) in saliva breaks down carbohydrates (sugars) A bolus (soft lump) is formed with saliva and the tongue

Step #2: Swallowing MAIN FUNCTION: Bolus is passed to the pharynx (throat) and the epiglottis makes sure the bolus passes into the esophagus and not down the windpipe!

Step #2: Swallowing (& not choking) Epiglottis flap of cartilage closes trachea (windpipe) when swallowing food travels down esophagus

Step #3: Esophagus and Peristalsis MAIN FUNCTION: Esophagus pushes food down to stomach Peristalsis = series of involuntary wave-like (smooth) muscle contractions  moves food DOWN the digestive tract

Step #4: Stomach Muscular sac  temporarily stores food Gastric juices are secreted Pepsin (enzyme) breaks down proteins Water Hydrochloric Acid (HCl) MAIN FUNCTION: Mechanically and chemically breaks down bolus Bolus  chyme (liquid food)

Step #5: Small Intestine MAIN FUNCTION = Most chemical digestion takes place here Nutrients are absorbed into blood More sugar and protein breakdown Amylase enzyme breaks sugars Trypsin enzyme breaks proteins Fats and DNA/RNA are also broken down Lipase Enzyme breaks down small fats Nuclease break down DNA/RNA

Step #5: Accessory Organs 1. Pancreas Makes pancreatic juice Contains trypsin, lipase, amylase, and nucleases AND sodium bicarbonate  neutralizes stomach acid Releases juice into small intestines

Step #5: Accessory Organs 2. Liver Makes bile What does bile do? Breaks down BIG fats pieces (globules) Emulsify fats

Step #5: Accessory Organs 3. Gallbladder stores bile Releases bile into small intestines

Absorption in Small Intestines Uses villi & microvilli finger-like projections increase surface area for absorption

VILLI

Step #6: Large Intestine (aka- the colon) MAIN FUNCTION= Water is absorbed using villi Feces (solid) is made undigestible solids (fibers) Rectum Holds solid wastes Releases feces from body through anus

Enzymes Involved in Digestion

Animation on Digestive System http://highered.mheducation.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html Quizzes (online to practice) http://www.mhhe.com/biosci/ap/holeessentials/student/olc/ap_animation-quizzes.html

Digestion and Homeostasis The endocrine, nervous, digestive and circulatory systems all work together to control digestion HOW DOES DIGESTIVE SYSTEM HELP MAINTAIN HOMESTASIS? Absorbing chemicals into blood (ex: calcium, glucose and nutrients)

Animation of Blood Glucose Regulation http://bcs.whfreeman.com/WebPub/Biology/hillis1e/Animated%20Tutorials/at3902/at_3902_insulin_glucose_reg.html

Disruption in Homeostasis (stomach) ULCERS erosion of the surface of the alimentary canal generally associated with some kind of irritant

Disruption in Homeostasis (water balance & large intestines) CONSTIPATION a condition in which the large intestine is emptied with difficulty. Too much water is reabsorbed the solid waste hardens

Disruption in Homeostasis (water balance & large intestines) DIARRHEA a gastrointestinal disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine This results in increased, multiple, watery feces This condition may result in severe dehydration, especially in infants

Disruption in Homeostasis (large intestines) APPENDICITIS an inflammation of the appendix due to infection Common treatment is removal of the appendix via surgery

Disruption in Homeostasis (Gallbladder) GALLSTONES an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder Can either be “passed” (OUCH!!) or surgically removed

Disruption in Homeostasis (stomach and esphogus) HEART BURN ACID from the stomach backs up into the esophagus