Unit D

Module 6 ~ Lesson 2

Structures of the Digestive System

To acquire nutrients from food, the body must process the food we eat mechanically and chemically. The digestive tract is a long tube starting with the mouth and ending with the anus. Everything in between is part of a complex and automatic response. It ensures that the food taken in ends up being converted to either usable molecules, which are absorbed, or to unusable waste products, which are eliminated. The digestive system also includes important accessory organs that are necessary for digestion.

Study the image and use it to label the organs of the digestive system in your Unit D diagram package. This package will be used several times in Unit D. Keep it handy for reference purposes.


Read page 217 and Figure 6.13 on page 218 of your textbook.

By BruceBlaus [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons

Digestion Begins

Digestion includes the physical and chemical breakdown of food. Breaking food down into smaller pieces is physical digestion. Chemical digestion is the process of breaking down large macromolecules into their subunits by enzymes. Digestion begins in the mouth with the physical breakdown of food by chewing and the chemical breakdown of starch by salivary amylase. The resulting lump of partially digested food is called a bolus and is moved to the stomach by contraction of smooth muscles in the esophagus.

By CNX OpenStax [CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons


Read "Digestion Begins: The Mouth and the Esophagus" on pages 218 to 219 of your textbook.