Digestion and Nutrient Absorption Presented by: Professor Steven Dion, Teresa Ward & Kelly Baker Salem State College - Sport, Fitness and Leisure Studies

Digestion and Nutrient Absorption

Presented by: Presented by:

Professor Steven Dion, Teresa Ward & Kelly BakerProfessor Steven Dion, Teresa Ward & Kelly Baker

Salem State College - Sport, Fitness and Leisure Studies Dept.Salem State College - Sport, Fitness and Leisure Studies Dept.

Digestion & Absorption - Dion, Ward & Baker

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Glossary of Terms DuodenumDuodenum – The first section of the small – The first section of the small

intestine. It is .3 meters long.intestine. It is .3 meters long. JejunumJejunum – The second section of the small – The second section of the small

intestine. It is 1-2 meters long.intestine. It is 1-2 meters long. IleumIleum – The third section of the small intestine. It – The third section of the small intestine. It

is 1.5 meters long.is 1.5 meters long. Hepatic Portal VeinHepatic Portal Vein – The vein that delivers – The vein that delivers

nutrients rich blood to the liver.nutrients rich blood to the liver. Esophageal SphincterEsophageal Sphincter – A gateway separating – A gateway separating

the esophagus and the stomach, controlling the the esophagus and the stomach, controlling the entry of food.entry of food.


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Glossary of Terms Pyloric sphincterPyloric sphincter – A gateway separating the – A gateway separating the

stomach and the small intestine, controlling the stomach and the small intestine, controlling the entry of chyme. entry of chyme.

ChymeChyme – A slushy acidic mixture of food and – A slushy acidic mixture of food and digestive juices.digestive juices.

Enzymes Enzymes – Protein molecules that increase the – Protein molecules that increase the speed of chemical reactions in the body. They speed of chemical reactions in the body. They work by combining with and altering the work by combining with and altering the molecules of other chemical substances. The molecules of other chemical substances. The digestive enzymes split large molecules of food digestive enzymes split large molecules of food into smaller units for absorption.into smaller units for absorption.


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Glossary of Terms

VilliVilli – Projections along the small intestinal – Projections along the small intestinal wall increasing area surface for greater wall increasing area surface for greater absorption.absorption.

HydrolysisHydrolysis – splitting of substances by – splitting of substances by adding wateradding water

GlycerolGlycerol – the combination of fats and – the combination of fats and oils.oils.


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The Odyssey The gastrointestinal tract:The gastrointestinal tract:

Includes the Includes the esophagus, gall bladder, liver, esophagus, gall bladder, liver, stomach, pancreas, small intestine, large stomach, pancreas, small intestine, large intestine, rectum, and anusintestine, rectum, and anus (which are both (which are both part of the large intestine). part of the large intestine).

Its entire length from the mouth to the anus Its entire length from the mouth to the anus is 6-8 meters long. is 6-8 meters long.

It is the tube that supplies nutrients and It is the tube that supplies nutrients and water to the body. water to the body.


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The GI Odyssey The nutrients are delivered to the liver by The nutrients are delivered to the liver by

way of the way of the hepatic-portal veinhepatic-portal vein and then they and then they are distributed throughout the body by the are distributed throughout the body by the circulatory system. circulatory system.

It takes the GI tract 1-3 days to eliminate the It takes the GI tract 1-3 days to eliminate the ingested food.ingested food.


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Mouth & Esophagus By chewing, grinding, mashing and softening food By chewing, grinding, mashing and softening food

particles, food becomes easier to swallow and particles, food becomes easier to swallow and becomes accessible to enzymes and other digestive becomes accessible to enzymes and other digestive substances that start the breakdown process. substances that start the breakdown process.

Smooth muscle contracts rhythmically causing the Smooth muscle contracts rhythmically causing the contents to move contents to move (peristalsis).(peristalsis).

This happens at zero gravity even if a person is This happens at zero gravity even if a person is turned upside down. turned upside down.

At the end of the esophagus is the esophageal At the end of the esophagus is the esophageal sphincter which is a one way ring of muscle that sphincter which is a one way ring of muscle that relaxes to allow the food to enter the stomach.relaxes to allow the food to enter the stomach.


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The Stomach

The stomach’s volume can range from .5 The stomach’s volume can range from .5 liters when empty to up to 6 liters when liters when empty to up to 6 liters when distended after an extremely large meal. distended after an extremely large meal.

Inside the stomach wall are gastric glands. Inside the stomach wall are gastric glands. These glands secrete hydrochloric acid and These glands secrete hydrochloric acid and other powerful enzyme containing digestive other powerful enzyme containing digestive juices that continually degrade the nutrients. juices that continually degrade the nutrients.


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The Stomach Carbohydrates are the easiest macronutrient Carbohydrates are the easiest macronutrient

to digest and leave the stomach most to digest and leave the stomach most rapidly, followed by proteins than fats. rapidly, followed by proteins than fats.

It takes between 1-4 hours to empty It takes between 1-4 hours to empty depending on the nutrient concentration and depending on the nutrient concentration and volume of the meal.volume of the meal.

The food mixes with a chemical substance The food mixes with a chemical substance called chyme, and then passes through the called chyme, and then passes through the pyloric sphincter into the small intestinepyloric sphincter into the small intestine


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The Small Intestine Approximately 90% of digestion (and essentially all Approximately 90% of digestion (and essentially all

lipid digestion) takes place in the first two sections of lipid digestion) takes place in the first two sections of the 3 meter long small intestine. the 3 meter long small intestine.

It is a coiled structure with three sections called the It is a coiled structure with three sections called the duodenum, jejunum and the ileum.duodenum, jejunum and the ileum.

There are tiny fingerlike protrusions along the walls There are tiny fingerlike protrusions along the walls of the small intestine called of the small intestine called villi.villi.

These structures absorb the carbohydrates, proteins, These structures absorb the carbohydrates, proteins, lipids, water, vitamins and minerals. lipids, water, vitamins and minerals.


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The Small Intestine The intestinal walls are made up of smooth muscle The intestinal walls are made up of smooth muscle

that contract and relax moving the food or chyme that contract and relax moving the food or chyme forward then slightly backward. forward then slightly backward. This gives the intestine additional time for This gives the intestine additional time for

absorption. absorption. Here the pancreas secretes 1.2-1.6 liters of alkali Here the pancreas secretes 1.2-1.6 liters of alkali

containing juice to help buffer the hydrochloric containing juice to help buffer the hydrochloric acid that mixes with the chyme and enters into acid that mixes with the chyme and enters into the small intestine from the stomach. the small intestine from the stomach.

Neutralizing this acid is crucial otherwise it causes Neutralizing this acid is crucial otherwise it causes ulcerations or ulcers.ulcerations or ulcers.


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The Large Intestine This is the final digestive structure. This is the final digestive structure. It consists of the It consists of the ascending and descending colon, ascending and descending colon,

transverse colon, sigmoid colon, rectum and anal transverse colon, sigmoid colon, rectum and anal canalcanal. It is 1.2 meters long. . It is 1.2 meters long.

By the time the digested food or chyme reaches the By the time the digested food or chyme reaches the large intestine, most of the nutrients have been large intestine, most of the nutrients have been absorbed. absorbed.

The primary role of the large intestine is to convert The primary role of the large intestine is to convert chyme into feces for excretion. chyme into feces for excretion.

Here the colon absorbs water from the chyme, Here the colon absorbs water from the chyme, changing it from liquid to solid. The large intestine changing it from liquid to solid. The large intestine does not contain villi.does not contain villi.


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The Digestive ProcessCarbohydrate digestion and absorptionCarbohydrate digestion and absorption Carbohydrates start breaking down in the mouth. Carbohydrates start breaking down in the mouth. The enzyme salivary amylase starts breaking up the The enzyme salivary amylase starts breaking up the

starches reducing it into smaller glucose molecules starches reducing it into smaller glucose molecules where in the stomach it continues to be broken where in the stomach it continues to be broken down further. down further.

Upon entering the small intestine the pancreas Upon entering the small intestine the pancreas releases the enzyme pancreatic amylase to help releases the enzyme pancreatic amylase to help complete the hydrolysis of starch into smaller complete the hydrolysis of starch into smaller chains of glucose molecules – monosaccharides, chains of glucose molecules – monosaccharides, which is 1 molecule of sugar. which is 1 molecule of sugar.


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The Digestive Process

(Carbohydrate digestion continued)(Carbohydrate digestion continued) The monosaccharides are absorbed into the The monosaccharides are absorbed into the

small intestine and delivered to the liver by small intestine and delivered to the liver by way of the hepatic portal vein. way of the hepatic portal vein.

After the liver processes the nutrients, the After the liver processes the nutrients, the nutrients enter into the blood stream nutrients enter into the blood stream circulating throughout the body. circulating throughout the body.


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The Digestive ProcessLipid or fat digestion and absorptionLipid or fat digestion and absorption In the stomach fats are broken down into glycerol In the stomach fats are broken down into glycerol

and fatty acids. and fatty acids. The digestion of fats starts in the stomach when The digestion of fats starts in the stomach when

mixed with the enzyme mixed with the enzyme lipase.lipase. The major part of the breakdown takes place in The major part of the breakdown takes place in

the small intestine. the small intestine. In the duodenum the enzyme In the duodenum the enzyme pancreatic lipasepancreatic lipase

furthers the process by breaking the fats down furthers the process by breaking the fats down from triglycerides to monoglycerides (which is 1 from triglycerides to monoglycerides (which is 1 fatty acid instead of 3 fatty acids connected to a fatty acid instead of 3 fatty acids connected to a glycerol molecule). glycerol molecule).


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The Digestive Process(Lipid/fat digestion and absorption continued)(Lipid/fat digestion and absorption continued) Bile is produce in the liver and secreted by the Bile is produce in the liver and secreted by the

gall bladder which increases the lipids solubility, gall bladder which increases the lipids solubility, breaking it down into droplets, making it easier breaking it down into droplets, making it easier for the small intestine to absorb. for the small intestine to absorb.

When foods with high lipid content enter the When foods with high lipid content enter the stomach, the hormone – stomach, the hormone – gastric inhibitory peptidegastric inhibitory peptide is released, slowing down movement flow out of is released, slowing down movement flow out of the stomach. the stomach.

This is why we feel full after eating high fat foods.This is why we feel full after eating high fat foods.


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Protein Digestion and AbsorptionProtein Digestion and Absorption Proteins are split into linked amino acids called Proteins are split into linked amino acids called

peptides and then into individual amino acids. peptides and then into individual amino acids. In the stomach the enzyme pepsin starts the In the stomach the enzyme pepsin starts the

breakdown of proteins into smaller units called breakdown of proteins into smaller units called polypeptides and peptides. polypeptides and peptides.

In the duodenum of the small intestine the In the duodenum of the small intestine the pancreatic enzymes trypsin and chymotyrpsin also pancreatic enzymes trypsin and chymotyrpsin also split proteins into polypeptides and peptides. split proteins into polypeptides and peptides.


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The Digestive Process(Protein Digestion and Absorption continued)(Protein Digestion and Absorption continued) In the jejunum of the small intestine an enzyme created In the jejunum of the small intestine an enzyme created

by the small intestine called peptidase splits the large by the small intestine called peptidase splits the large peptides into smaller peptides and than into amino acids. peptides into smaller peptides and than into amino acids.

All of these smaller protein fragments go directly to the All of these smaller protein fragments go directly to the liver by the hepatic portal vein. liver by the hepatic portal vein.

Once in the liver one of three things happens to the Once in the liver one of three things happens to the proteins: proteins: 1. It converts to glucose, 1. It converts to glucose, 2. It converts to fat or 2. It converts to fat or 3. It is directly released into the blood as amino acids.3. It is directly released into the blood as amino acids.


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Vitamin Absorption Vitamin Absorption Vitamins are absorbed mainly in the Vitamins are absorbed mainly in the

jejunum and ileum sections of the small jejunum and ileum sections of the small intestine. A, D, E, and K are the fat soluble intestine. A, D, E, and K are the fat soluble vitamins and they must be absorbed in vitamins and they must be absorbed in combination with fat. combination with fat.

Fat is the transport for which the vitamins Fat is the transport for which the vitamins are delivered to the liver. are delivered to the liver.


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(Vitamin Absorption Continued)(Vitamin Absorption Continued) The B’s and C vitamins are water soluble The B’s and C vitamins are water soluble

vitamins. vitamins. They start breaking down in the stomach They start breaking down in the stomach

and then throughout the small intestine. and then throughout the small intestine. They do not remain in the body’s tissues They do not remain in the body’s tissues

very long and the excess is passes on into very long and the excess is passes on into the urine.the urine.


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Mineral AbsorptionMineral Absorption Intestinal absorption of minerals increases Intestinal absorption of minerals increases

when the body is lacking the particular when the body is lacking the particular nutrient. nutrient.

Intestinal absorption of minerals decreases Intestinal absorption of minerals decreases when the body is not lacking the particular when the body is not lacking the particular nutrient. nutrient.


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Water AbsorptionWater Absorption Saliva, gastric secretions, bile, pancreatic acids and Saliva, gastric secretions, bile, pancreatic acids and

intestinal secretions take up approximately 7 liters intestinal secretions take up approximately 7 liters of water, when combined with an intake of an of water, when combined with an intake of an average of 2 liters of water ingested, the body is average of 2 liters of water ingested, the body is processing approximately 9 liters of water daily. processing approximately 9 liters of water daily.

72% is absorbed in the first half of the small 72% is absorbed in the first half of the small intestine, 20% is absorbed in the lower half of the intestine, 20% is absorbed in the lower half of the small intestine, and 6% is absorbed in the large small intestine, and 6% is absorbed in the large intestine.intestine.


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Digestion and Nutrient Absorption Presented by: Professor Steven Dion, Teresa Ward & Kelly Baker Salem State College - Sport, Fitness and Leisure Studies