Life Science 3.1 : The Digestive SystemPresentation Transcript
Life Science Chapter 3 The Digestive and Urinary Systems
Life Science 3.1 The Digestive System
Objective: Compare mechanical digestion with chemical digestion. Describe the parts and functions of the digestive system. View slide
Digestive System at a Glance Digestive system 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. View slide
Breaking Down Food Mechanical digestion Breaking, crushing, and mashing of food. Chemical digestion Large molecules are broken down into nutrients with the aid of enzymes.
Digestion Begins in the Mouth Teeth With the help of strong jaw muscles, teeth break and grind food. Saliva Contains an enzyme that begins the chemical digestion of carbohydrates.
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 tube called the esophagus.
Stomach Muscular, saclike, digestive organ attached to the lower end of the esophagus. Tiny glands in the stomach Produce enzymes and acid 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. The Harsh Environment of the Stomach
The Pancreas and Small Intestine Pancreas Organ located between the stomach and small intestine. Makes fluids that protect the small intestine from the acid in chyme. Small Intestine Muscular tube that is about 2.5 cm in diameter and about 6 m long. Nutrients are absorbed into the bloodstream through fingerlike projections called villi.
The Liver and the Gallbladder Liver Large, reddish brown organ that helps with digestion by making bileto break up fat. Stores excess nutrients until the body is ready to absorb them into the bloodstream. Breaks down toxins. Gallbladder Saclike organ that stores bile Squeezes the bile into the small intestine. Breaks large fat droplets into smaller ones.
The End of the Line Large intestine Wider and shorter portion of the intestine that removes water from mostly digested food and that turns the waste into semisolid feces, or stool. Feces are stored in the rectum until they can be expelled. About 1.5 m long, 7.5 cm diameter
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. Digestive system visual concept