Digestive System:pp. 900-911

• Pre-Movie:http://kidshealth.org/kid/closet/movies/how_the_body_works_interim.html

• Major structures:– Mouth– Throat– Esophagus– Stomach– Liver– Pancreas– Small and large intestines

http://www.encognitive.com/images/digestive-system-2.jpg

Digestive System Key Functions

• Extracts and absorbs nutrients from food• Removes wastes• Maintains water and chemical balances

Key terms

• Nutrient – a substance required by the body for energy, growth, repair, and maintenance. Nutrients in food and beverages include:

• Carbohydrates• Lipids• Proteins• Vitamins• Minerals

• Digestion – the process of breaking down food into molecules the body can use

• calorie – a unit by which the energy available in food is measured• It is the amount of heat energy required to raise the temperature of 1g of

water 1oC• A calorie is actually a very small amount of energy so nutritionists use a unit

called the Calorie (with a capital C) which is equal 1,000 calories

http://static.howstuffworks.com/gif/calorie.gif

Terms Cont’d• Carbohydrates – sugars • Proteins – amino acids• Lipids – fats• Vitamins – organic substances that occur in many foods in small

amounts and are necessary in trace amounts for the normal metabolic functioning of the body (e.x. fat-soluble vitamins – A, D, E, K; water-soluble vitamins – C and B)

• Minerals – naturally occurring inorganic substances that are used to make certain body structures and substances, for normal nerve and muscle function, and to maintain osmotic balance. Your body doesn’t produce them, rather you need to intake them.

• Teeth and bones require calcium and phosphorus• Iron is needed for the transportation of oxygen• Magnesium, calcium, sodium, potassium, and zinc help regulate function of the

nerves and muscles

From Mouth to Anus

• Food travels more than 26 feet through your digestive tract, which consists of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and rectum

• The liver and pancreas are not part of the tract, but they deliver secretions into the tract through tubes called ducts http://www.surgery.uthscsa.edu/surgicaloncology/pancreas.jpg

Pathway Cont’d• In your mouth, teeth rip and chew

food. Also, saliva contains enzymes (amylases) that begin to help breakdown carbohydrates

• Esophagus connects the mouth to the stomach through a valve called a sphincter– Stomach is just beneath the diaphragm

• Stomach: temporarily stores food and also breaks it down– Gastric juice is secreted by the cells

that line the inside of the stomach, and it is made up of hydrochloric acid and pepsin

http://graphics8.nytimes.com/images/2007/08/01/health/adam/8756.jpg

Pathway Cont’d• Food passes from the stomach

into the small intestine with a sphincter– Digestion and absorption of

nutrients• The first part of the small

intestine (duodenum) receives secretions from the pancreas, liver, and gallbladder

• Liver produces bile (helps break down fats) which is stored in the gallbladder and released to the small intestine

• Most absorption, or passage of nutrients to the blood or lymph, occurs in the small intestine

Pathway Cont’d• Food wastes move into the large

intestine (colon); no digestion takes place here– Mostly mineral ions and water are

absorbed through the wall of the large intestine

• Bacteria in your colon help make compounds your body needs (ex. vitamin K and several B vitamins) but also help transform and compact the undigested materials into feces

• The final segment of the large intestine is called the rectum and from the rectum the solid feces are eliminated from the body through the anus http://pennstatehershey.org/healthinfo/graphics/images/en/10255.jpg

http://curezone.com/upload/_N_Forums/Natural_Heali/f26_1_digestive_system_c.jpg

Diarrhea

• When wastes are rushed through the large intestine before the remaining water is absorbed = watery feces

http://tell.fll.purdue.edu/JapanProj/FLClipart/Medical/diarrhea.gif

Constipation (hard feces)

• When food remains in the colon for long periods of time, which causes much water to be absorbed

http://www.dollymix.tv/parent_constipation1.gif

More about your liver

• Open and read “The Liver’s Role in Digestion” and “The Liver’s Role in Metabolism” on pages 910-911

Modeling the Function of Bile

• Quick Lab Activity, p. 911 DEMO

Digestive System Practice

• Do all three activities at http://www.harcourtschool.com/activity/digest/index.htm– Building Your System– Inside Story– Food Path

• http://msjensen.cehd.umn.edu/Webanatomy/timed/31.htm

• http://www.ugoplayer.com/games/digestivesystem.html

• http://nature.ca/discover/exm/blddgstvsystm/index_e.cfm