Ch 39 – Digestion & Excretion 39.2 Digestive system 39.3 Excretory system

Digestion is the breaking down of organic matter Mechanical digestion Chemical digestion

39.2 Digestive system Ingest food. Transport food. Digest food into smaller usable components. Absorb the necessary nutrients into the bloodstream. Expel the waste products from the body.

Path of digestion & excretion

Start of digestion - Mouth Chem & mechanical Saliva moistens & lubricates food Salivary amylase begins to break down starches (carbohydrates).

Esophagus Approximately 10” long No digestion Moves food from the throat to the stomach Muscle movement called peristalsis If acid from the stomach gets in here that’s heartburn. A good way to describe peristalsis is an ocean wave moving through the muscle. These diagrams don’t separate the esophagus from the mouth functions, you might want to talk about what happens in the mouth too.

Stomach Sphincter separates esophagus & stomach Stores the food you eat, breaks it down into tiny pieces –mech & chem Mixes food with digestive juices HCl and pepsin Pepsin digests large proteins into smaller proteins Mucus, bicarbonate, and blood circulation helps protect stomach tissues The stomach takes around 4 hours to do it’s job on the food, depending on what kinds of food are digested.

Small Intestine Small intestines are roughly 20 feet long Insides are coated with little ‘fingers’ called villi to increase surface area. Lipases break down fat Nutrients from the food pass into the bloodstream through the small intestine walls.

Small Intestine Pancreas Liver Gall bladder ** Most chemical digestion takes place in the small intestine with help of secretions from the Pancreas Liver Gall bladder Villus singular Villi plural

Large Intestine or Colon About 5 feet long, not coiled No digestion Accepts what small intestines don’t absorb. Absorbs water and minerals from the waste matter. Last section is rectum Depending on the maturity of the group, you can talk about the feces leaving via the anus. Mention the appendix at the bottom of the ascending colon and that it might have been used long ago but is not today Mention the portions of the large intestine, ascending, transverse, descending, sigmoid, and rectum (last one if the audience is mature enough)

Function of appendix – growing fetus: endocrine system, adult : immne system

Pancreas Produces compounds to digest fats and proteins Neutralizes acids that enter small intestine Regulates blood sugar by producing insulin Explain the difference between the two types of diabetes. In type 1, the pancreas fails to produce enough insulin. In type 2, the body stops responding properly to the insulin it creates.

Liver Directly affects digestion by producing bile Bile helps digest fat Processes nutrients in the blood, filters out toxins and waste. Is often called the body’s energy factory About the size of a football (3 lbs) in a human Livers can regenerate missing pieces if necessary. Is one of the largest organs in the body.

Gall Bladder Stores bile from the liver Delivers bile when food is digested Fatty diets can cause gallstones Explain to students that removing the stones typically means removing the gallbladder, but that the body eventually adjusts to not having the bile stored.

Digestive system video

39.3 Excretion 3 organs LUNGS KIDNEYS SKIN Excretion is the process that rids the body of toxic chemicals, excess water, salts, CO2, while maintaining osmotic & pH balance 3 organs LUNGS KIDNEYS SKIN

Kidneys Each kidney is composed of about 1 million microscopic blood filtering units called nephrons Kidneys filter out blood toxins urea (ammonia converted to less toxic nitrogenous waste) water salts 3 phases Filtration Reabsorption Secretion

Kidney – science facts Your blood passes through the kidneys 300 x a day. The nephrons clean all your blood in 45 min.  Every day the nephrons send about 6 cups of urine to the bladder.

Function of the nephron

Urine – formed from the water, urea, & salts that are left after absorption & secretion Ureters – tubes that carry urine from kidney to urinary bladder Urethra – urine leaves body and exits via urethra

Digestive Enzymes Pepsin Lipase large proteins into smaller proteins Amylase Pepsin Lipase fats into fatty acids and glycerol starches into sugars stomach large proteins into smaller proteins mouth intestine 3

Mini quiz Proteins are made up of Fatty acids Glycerol Amino acids monosaccharides

During digestion, food passes through the mouth, esophagus, stomach, ________, & large intestine. Pancreas Lungs Gallbladder Small intestine

Which of the following correctly pairs the enzymes with the food molecules they digest? Lipases – starch Amylases – fats Lipases – fats Pepsin – starches

Which substance is NOT a waste eliminated from the body through the kidneys? A. Urea Water Salts Oxygen

The ________ are involved in excretion Kidneys & stomach Liver & pancreas Pancreas & kidneys Kidneys & lungs