Assimilation of Food in the Digestive System

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  • 0:03 What Is Assimilation?
  • 0:29 Human Digestion
  • 1:10 Assimilation of Nutrients
  • 2:36 Assimilation of Water
  • 3:52 Other Digestive Systems
  • 5:11 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson, we'll be learning about the biological process of assimilation and its role in the digestive system. We'll learn how this happens in humans and compare it to other animals.

What Is Assimilation?

At some point today, you probably ate a meal or a snack to get some energy, but have you ever thought about how that food gets from your plate into your cells? After you eat, your body breaks down food during digestion, absorbs the nutrients, and distributes them to cells during assimilation. Assimilation gets the nutrients from your food to your cells where they are used for growth and repair.

Human Digestion

To understand assimilation, let's first look at how we digest a typical meal: a cheeseburger. When we first bite into the cheeseburger, your teeth macerate the food, grinding it as your tongue turns it into a bolus, which then travels through your esophagus to your stomach.

As the cheeseburger bolus enters the stomach, strong acids and enzymes break it apart. The carbohydrates and proteins are the first to go, the bun and meat of your burger. Next, in the small intestine, fats, like the grease and cheese, start to break down into their individual components, called fatty acids. At this point, the digestion of your cheeseburger is complete. It's now time to assimilate the nutrients into your body.

Assimilation of Nutrients

Assimilation of nutrients happens in the small intestine. Your small intestine is equipped with tiny projections called microvilli on the surface of the cells lining the intestine, called epithelial cells. These important cells take nutrients from the intestine and pump it into your blood, where it can be distributed to the body. To understand this process, let's look at how carbohydrates are assimilated specifically.

By the time the carbohydrates in your burger bun reach the small intestine, they are broken down into individual sugars, like glucose. The microvilli contain small pumps that take sugar from the intestinal lumen and move it into the intestinal epithelial cells. However, to get the sugar to the rest of the body, it needs to enter the blood stream. The other side of the intestinal epithelial cells has another pump that shuttles glucose into the blood vessels that surround the intestine.

Too much glucose in the blood can cause serious problems, so next, blood flows to the liver to deliver glucose for storage. Liver cells can store excess glucose as glycogen. From there, the glucose is delivered to all the cells in your body. Your cells use glucose to make cellular energy, or ATP. The ATP produced is used to make everything the cell needs, such as proteins to help it divide, grow, move, and do any jobs needed for the body.

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