![]() ![]() Infants have a few special adaptations that allow them to digest fat effectively. ![]() So, how do babies digest all of the fat in their diet? Yet, infants are born with low levels of bile and pancreatic enzyme secretion, which are essential contributors to lipid digestion in older children and adults. Whether breastfed or formula-fed, fat provides about half of an infant’s calories, and it serves an important role in brain development. Breast milk contains about 4 percent fat, similar to whole cow’s milk. Lipids are an important part of an infant’s diet. Special Adaptations for Lipid Digestion in Infants VIDEO: “Lipids -Digestion and Absorption,” by Alice Callahan, YouTube (November, 17, 2019), 8:49 minutes. We’ll learn more about other types of lipoproteins on the next page. Chylomicrons from the small intestine travel first into lymph vessels, which then deliver them to the bloodstream.Ĭhylomicrons are one type of lipoprotein-transport vehicles for lipids in blood and lymph. This outer membrane makes them water-soluble so that they can travel in the aqueous environment of the body. Chylomicrons are large structures with a core of triglycerides and cholesterol and an outer membrane made up of phospholipids, interspersed with proteins (called apolipoproteins) and cholesterol. Long-chain fatty acids and monoglycerides reassemble into triglycerides within the intestinal cell, and along with cholesterol and fat-soluble vitamins, are then incorporated into transport vehicles called chylomicrons. Once inside the intestinal cell, short- and medium-chain fatty acids and glycerol can be directly absorbed into the bloodstream, but larger lipids such as long-chain fatty acids, monoglycerides, fat-soluble vitamins, and cholesterol need help with absorption and transport to the bloodstream. Lipid digestion and absorption in the small intestine. ![]() The products of fat digestion diffuse across the membrane of the intestinal cells, and bile salts are recycled back to do more work emulsifying fat and forming micelles.įigure 5.22. Bile salts cluster around the products of fat digestion to form structures called micelles, which help the fats get close enough to the microvilli of intestinal cells so that they can be absorbed. Next, those products of fat digestion (fatty acids, monoglycerides, glycerol, cholesterol, and fat-soluble vitamins) need to enter into the circulation so that they can be used by cells around the body. Lipid Absorption from the Small Intestine Cholesterol and fat-soluble vitamins do not need to be enzymatically digested (see Fig. #FITDAY REGISTRATION KEY FREE#Triglycerides are broken down to fatty acids, monoglycerides (glycerol backbone with one fatty acid still attached), and some free glycerol. The pancreas secretes pancreatic lipases into the small intestine to enzymatically digest triglycerides. Emulsification makes lipids more accessible to digestive enzymes by increasing the surface area for them to act (see Fig. This makes them effective emulsifiers, meaning that they break large fat globules into smaller droplets. Bile salts have both a hydrophobic and a hydrophilic side, so they are attracted to both fats and water. Bile, which is made in the liver and stored in the gallbladder, is released into the duodenum, the first section of the small intestine. Lipid Digestion in the Small IntestineĪs the stomach contents enter the small intestine, most of the dietary lipids are undigested and clustered in large droplets. Overview of lipid digestion in the human gastrointestinal tract. But together, these two lipases play only a minor role in fat digestion (except in the case of infants, as explained below), and most enzymatic digestion happens in the small intestine.įigure 5.21. Lingual lipase swallowed with food and saliva also remains active in the stomach. Cells in the stomach produce another lipase, called gastric lipase (“gastric” means relating to the stomach) that also contributes to enzymatic digestion of triglycerides. In the stomach, mixing and churning helps to disperse food particles and fat molecules. An enzyme called lingual lipaseis produced by cells on the tongue (“lingual” means relating to the tongue) and begins some enzymatic digestion of triglycerides, cleaving individual fatty acids from the glycerol backbone. Chewing mechanically breaks food into smaller particles and mixes them with saliva. Lipid Digestion in the MouthĪ few things happen in the mouth that start the process of lipid digestion. Let’s start at the beginning to learn more about the path of lipids through the digestive tract. ![]()
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