The Digestive System Chapter 3 Section 1

Digestive System 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

Digestion 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 acidsStorage and energy

Mouth 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.

Stomach 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 & 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 & Gallbladder 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 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)

Diagram