Chapter 3 Section 1

• Organs that break down food so it can be used by the body.
• Food passes through a long tube called the digestive tract.
• Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus
• There are other organs in the digestive system that food doesn’t pass through:
• Liver, gallbladder, pancreas, salivary glands

• Breaking down food- 2 possible ways:
• Mechanical digestion: breaking, crushing, mashing food. (smaller pieces)
• Chemical digestion: breaking apart large molecules into smaller nutrient molecules. (chemically different molecule)
• Enzymes help break apart large molecule chains into smaller nutrients
• 3 types of nutrients
• Carbohydrates  sugar (glucose) Energy
• Proteins  amino acids Build body materials
• Fats  fatty acids Storage and energy

• Teeth are used to chew food (mechanical digestion)
• Saliva has enzymes that begin breaking down carbs into sugars
(chemical digestion)
• Tongue helps push food into the esophagus- a tube coming off the pharynx (along with the trachea)
• Epiglottis: covers the trachea when you swallow.
• Peristalsis: a wave of muscle contraction that pushes food along the digestive tract.

• A saclike, muscular organ at the end of the esophagus
• Muscles contract to squeeze food (mechanical digestion)
• Glands produce enzymes and acid to break food into nutrients
(chemical digestion)
• Stomach acid also kills any bacteria.
• Chyme- the soupy mixture of broken down food and digestive juices
• Stomach stores food for a while and slowly lets it out into the small intestine.
• Sphincter- ring of muscle that opens and closes like a valve
• Cardiac (lower esophageal)- esophagus into stomach
• Pyloric- stomach into small intestine

• Pancreas- secretes digestive enzymes into the small intestine and produces hormones to regulate blood sugar levels.
• Small intestine is about 20 feet long, but is only 1 inch in diameter.
• Most digestion and absorption occur in small intestine.
• Villi- Fingerlike projections that increase the surface area and are covered with nutrient absorbing cells that put nutrients into bloodstream.

• Liver is a large (football size), reddish-brown organ that helps with digestion:
• Produces bile which breaks up (emulsifies) fats
• Stores nutrients and regulates absorption into blood
• Removes toxins
• Gallbladder: Stores bile for release into small intestine

• Large intestine is only about 5 feet long, but is 2.5 inches in diameter.
• Materials that couldn’t be absorbed are pushed into the large intestine.
• Large intestine stores, compacts, and eliminates indigestible wastes from the body.
• Water is absorbed from the mixture and the liquid becomes semi-solid material called feces or stool (aka. poop).
• Fiber helps keep materials moving in digestive system.
• Rectum- Stores feces until it can be passed out of the body through the anus (another sphincter)