Like?

Lipids Digestion and Absorption

Start Your Free Trial To Continue Watching
As a member, you'll also get unlimited access to over 8,500 lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed.
Free 5-day trial
It only takes a minute. You can cancel at any time.
Already registered? Login here for access.
Start your free trial to take this quiz
As a premium member, you can take this quiz and also access over 8,500 fun and engaging lessons in math, English, science, history, and more. Get access today with a FREE trial!
Free 5-day trial
It only takes a minute to get started. You can cancel at any time.
Already registered? Login here for access.
  1. 0:05 Lipids
  2. 0:54 Bile Salts and Pancreatic Lipase
  3. 1:59 Epithelial Cells
  4. 2:54 Chylomicrons and Lacteals
  5. 4:23 Lesson Summary
Show Timeline
Taught by

Rebecca Gillaspy

Dr. Becky has taught health science courses at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic

Lipids, or fats, are digested and absorbed in the small intestine. In this lesson you will learn how bile salts emulsify fat so pancreatic lipase can digest it. You will also learn how fats first enter lymphatic capillaries, called lacteals, before entering your blood circulation.

Lipids

Foods, such as meats, dairy products, seeds, nuts, and oils, contain dietary fat. Fat is a common example of a lipid, and in this lesson you will learn about the unique way lipids, such as fats, are broken down and absorbed out of the digestive tract.

A lipid is defined as a fat-like molecule that does not have the ability to dissolve in water. This inability to dissolve in water adds an element of difficulty to fat digestion. Because fat does not like water, it tends to clump together and form large droplets as it moves through your digestive system. By the time fat reaches your small intestine, it has not been digested at all. So dietary fat in the small intestine looks like a fairly large glob of fat.

Lipids are fat-like molecules that cannot dissolve in water
Lipids

Bile Salts and Pancreatic Lipase

These globs remain until bile that is produced in the liver and stored in the gallbladder mixes with the large fat droplets. Bile contains bile salts, which act as an emulsifier of lipids. The term 'emulsify' means to break large fat droplets into smaller droplets. And that is exactly what we see happening here in the small intestine. The bile salts break up and coat the fat to form much finer droplets. These finer droplets have more surface area, and this aids digestion because the fat-digesting enzyme pancreatic lipase can only act on the surface of the fat droplet.

The enzymes of the small intestine are responsible for almost all of the fat digestion. When pancreatic lipase acts on the lipid, it breaks it down, which results in free fatty acids and monoglycerides, the two digestive products of lipids. These products are much easier for your small intestine to handle, and they have very little trouble being absorbed out of your digestive tract.

Pancreatic lipase breaks lipids down into free fatty acids and monoglycerides
Digestive Products of Lipids

Epithelial Cells

Absorption takes place through the mucosal lining of the small intestine, and when these products pass through the mucosa, they enter the epithelial cells. Once inside the cells, the free fatty acids and monoglycerides enter the endoplasmic reticulum, which is a system inside the cell whose functions include synthesis and transport of lipids. Here, the digested products are resynthesized into triglycerides. Triglycerides are the major form of fat stored by the body. So an important fact to point out is that fats are reassembled in the epithelial cells of the small intestine. This makes fat absorption different than absorption of proteins and carbohydrates. With protein and carbohydrate absorption, we see their basic units, which are amino acids and monosaccharides, are able to pass through the intestinal epithelial cells without being altered.

Chylomicrons and Lacteals

Before triglycerides actually leave the epithelial cells, they're coated by proteins, which results in the formation of chylomicrons. So we see that chylomicrons are small globules composed of protein and lipid. The coating of protein gives the triglyceride a water-soluble coat, and this allows the chylomicron to travel outside of the cell. The newly formed chylomicrons leave the epithelial cell and enter the lymphatic capillaries, which are called lacteals. The lacteals are found in the fingerlike projections of the intestinal wall, called the villi. The lacteals represent another unique way fats are absorbed because lipids pass through the lymphatic system before they make their way back to your bloodstream.

Chylomicrons enter the lymphatic capillaries, which are called lacteals
Chylomicrons

This differs from protein and carbohydrate digestion because amino acids and monosaccharides do not enter the lymphatic system; instead they travel directly into the blood capillaries and then into the hepatic portal vein that leads to the liver.

Fats can now travel around your body. They are used to build cell membranes, make the myelin sheathes that coat your nerves, and of course insulate the body with a fatty cushion. Fats can also be used as fuel for your body if there are not enough carbohydrates in your system. Although you need fats for these important body functions, you can have too much of a good thing. For example, a high level of triglycerides in your blood can increase your risk of heart disease.

Lesson Summary

Let's review. A lipid is defined as a fat-like molecule that does not have the ability to dissolve in water. Lipids, or fat, go undigested in your digestive tract until they reach your small intestine, where they meet bile. Bile contains bile salts, which act as an emulsifier of lipids. This breaks the large fat droplets into smaller droplets that are then easier for the fat-digesting enzyme pancreatic lipase to digest.

When pancreatic lipase acts on the small lipid droplets, it breaks them down into free fatty acids and monoglycerides, which are the two digestive products of lipids. These small units are able to pass through the intestinal mucosa and enter the epithelial cells of the small intestine. Once inside the cells, they enter the endoplasmic reticulum, which is a system inside the cell whose functions include synthesis and transport of lipids. Here, the digested products are resynthesized into triglycerides, which are the major form of fat stored by the body. Before the triglyceride leaves the cell, they get a protein coating and become chylomicrons. Chylomicrons are small globules composed of protein and lipid. The chylomicrons first enter lymphatic capillaries called lacteals before entering the general blood circulation.

Fats are used to build cell membranes, make myelin sheathes, insulate the body or as an alternate fuel source.

People are saying…

"This just saved me about $2,000 and 1 year of my life." — Student

"I learned in 20 minutes what it took 3 months to learn in class." — Student

See more testimonials

Did you like this?
Yes No

Thanks for your feedback!

What didn't you like?

What didn't you like?

Congratulations! You've reached the last video in the chapter.
Start the Next Chapter
Create your Account

Sign up now for your account. Get unlimited access to 8,500 lessons in math, English, science, history, and more.

Meet Our Instructors

Meet all 53 of our instructors

Copyright