The Digestive System - tcss.net · 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

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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


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Section 1 The Digestive SystemChapter 24



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.











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




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.







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)




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.




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.


















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.




The Liver and the Gallbladder, continued




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.




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.


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The Digestive System - tcss.net · 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