The Digestive System - Tuscaloosa County School System ... · Title: Microsoft PowerPoint - The...
Transcript of The Digestive System - Tuscaloosa County School System ... · Title: Microsoft PowerPoint - The...
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Section 1 The Digestive System
Digestive System at a Glance
• Your digestive system is a group of organs that break down food so that it can be used by the body.
• Food passes through the digestive tract. The digestive tract includes your mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus.
• The liver, gallbladder, pancreas, and salivary glands are also part of the digestive system.
Chapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Breaking Down Food
• The breaking, crushing, and mashing of food is called mechanical digestion.
• In chemical digestion, large molecules are broken down into nutrients with the aid of enzymes.
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Digestion Begins in the Mouth
• Teeth - With the help of strong jaw muscles, teeth break and grind food.•Incisors - shred/cut•Canines – shred/tear•Pre-molars – mash•Molars - grind
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Digestion Begins in the Mouth, continued
• Saliva contains an enzyme that
begins the chemical digestion of
carbohydrates (sugars).
•Taste Buds – Nerve centers on the tongue that detect sweet, sour,
bitter, and salty flavors.
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Digestion Begins in the Mouth, continued
•Leaving the Mouth Once the food has been
reduced to a soft mush, the tongue pushes it
into the throat, which leads to a long, straight,
slippery tube called the esophagus. The
esophagus is about 25 cm long and food
travels down it due to gravity and peristalsis
(wave of rhythmic muscle contractions that
push the food through the tube)
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
The Harsh Environment of the Stomach
• The stomach is a muscular, saclike, digestive organ attached to the lower end of the esophagus.
• Tiny glands in the stomach produce enzymes and acid (HCl) to break food down into nutrients.
• After a few hours of combined mechanical and chemical digestion, food leaves your stomach as a soupy mixture called chyme.
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
The Pancreas and Small Intestine
• The Pancreas is an organ located between the stomach and small intestine. Its makes pancreatic fluids that protect the small intestine from the acid in chyme and releases insulin to help regulate blood sugar.
• The Small Intestine is a muscular tube that is 2.5 cm in diameter, but about 6 meters (20 ft) long! In the small intestine, nutrients are absorbed into the bloodstream through fingerlike projections called villi.
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu ResourcesChapter menu
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
The Liver and the Gallbladder
• The liver is a large, reddish brown organ that helps with digestion by making bile to break up fat.
• Bile is stored in a saclike organ called the gallbladder, which squeezes the bile into the small intestine.
• The liver also stores excess nutrients until the body is ready to absorb them into the bloodstream.
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
The Liver and the Gallbladder, continued
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
The End of the Line
• Material that can’t be absorbed into the blood is pushed into the large intestine.
• The large intestine is a horseshoe-shaped tube that is 6.5 cm in diameter and about 1.5 meters long. It absorbs most of the water in undigested material and changes the liquid into semisolid waste material called feces, or stool.
• Feces are stored in the rectum until they can be expelled.
Section 1 The Digestive SystemChapter 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
ResourcesChapter menu
The End of the Line, continued
• Feces pass to the outside of the body through an opening called the anus.
• It has taken each of your meals about 24 hours to make this journey through your digestive system.
Section 1 The Digestive SystemChapter 24