Where it happens, How it works, and Why it’s important DIGESTION Where it happens, How it works, and Why it’s important

3 primary functions of the digestive system Break down food Is this hydrolysis or dehydration synthesis? Absorb nutrients (monomers) & water Remove waste (non-digestible material)

Where it happens... Digestive TRACT = Mouth Esophagus Stomach Small intestine Large intestine Digestive SYSTEM Includes organs that contribute digestive juices

The Mouth Chewing increases surface area Saliva: Wets the food & mixes it with mucus Salivary amylase breaks starches into disaccharides Kills off dangerous microbes

The Esophagus Swallowing closes off the trachea via the epiglottis Peristalsis begins NO ENZYMES here

The Stomach Here for 2-3 hours Storage Liquifies to form chyme Pepsin (requires acidic pH of 1...HCl does this)

The Small Intestine Duodenum Pancreatic juice (from pancreas) Amylase Lipase Protease Sodium bicarbonate neutralizes acid Bile (from liver via gallbladder) salts increase lipid surface area by emulsification - Intestinal juice (from small intestine) Maltase, lactase, sucrase Protease

Nutrient Absorption In the small intestine Molecules have to be small Villi What is left? Water, cellulose & other non-digestible matter

The Appendix For humans, unused in digestion In other mammals, it stores cellulose and other nutrient remains at this point in digestion (Fun Fact: current science says it is used in our immune system to help identify antigens in food)

The Large Intestine (the Colon) Water diffuses into the blood Bacteria live here in symbiosis with us

The Breakdown: MOLECULES: Carbohydrates Proteins Lipids WHERE DIGESTED: Mouth, small intestine Stomach, small intestine Small intestine

Gross Facts Bacteria love the stuff we can’t break down…and gas & flatulence are caused by bacteria metabolizing these nutrients 99% of these gases are odorless People actually study these gases to find out the 1% of these gases that cause the odors (great job!) Feces is 1/2 bacteria by weight

Gross Facts Newborns don’t pass gas because they have no bacteria in their intestines yet Beano breaks down some molecules the bacteria like Lactaid breaks down lactose Gas-X reduces the surface tension of gas bubbles, which makes you feel better….but the gas is still there Passing gas in public in ancient Rome was against the law

To see and hear digestion in action: ** http://www.kidshealth.org/misc_pages/bodyworks/digest.html