Chapter 15 Section 3: Final Digestion and Absorption Key concepts: What digestive processes occur in the small intestine, and how are other digestive organs involved? What role does the large intestine play in digestion? Key terms: small intestine, liver, bile, gallbladder, pancreas, villus, large intestine, rectum, anus

Small intestine The small intestine is part of the digestive tract where most chemical digestion takes place It is 6 meters long, but named for its small diameter Food is already a thick liquid when it reaches the small intestine, but chemical digestion is really just beginning. Almost all chemical digestion and absorption of nutrients occur in the small intestine.

The liver The liver is located in the upper right portion of the abdomen. It is the largest organ inside the body. It breaks down medicines and helps eliminate nitrogen from the body It produces bile – a substance that breaks up fat particles.

Liver to the gallbladder After bile leaves the liver, it flows to the gallbladder, the organ that stores bile. After you eat, bile passes through a tube from the gallbladder into the small intestine.

On Bile Bile is not an enzyme It does break up large fat particles into smaller fat droplets that are then chemically broken down by enzymes produced in the pancreas

The pancreas The pancreas is a triangular organ that lies between the stomach and the first part of the small intestine. It produces enzymes that flow into the small intestine and help break down starches, proteins, and fats Fiber isn’t broken down, and helps push stuff through the small intestine

Absorption in the small intestine The inner surface of the small intestine looks bumpy because it has millions of tiny structures called villi. They absorb nutrient molecules which then pass into blood vessels.

The large intestine By the time material reaches the large intestine (named for its diameter), most nutrients have been absorbed. The large intestine is about 1.5 meters long and runs up the right hand side of the abdomen. The large intestine contains bacteria that feed on the material passing through. These bacteria make vitamins like vitamin K. Water is absorbed back into the blood stream.. Ends in the rectum – a short tube. The rectum ends with the anus – a muscular opening.