Digestion, Absorption and Metabolism
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Transcript Digestion, Absorption and Metabolism
Digestion, Absorption and Metabolism
Presented by
Janice Hermann, PhD, RD/LD
OCES Adult and Older Adult Nutrition Specialist
What Is Digestion
Process whereby the body breaks down food
into absorbable nutrients.
Digestive tract is a long tube surrounded by
muscles.
The muscles alternate contracting and
relaxing pushing food along.
Mouth
Teeth grind food to reduce the size.
Saliva released to help moisten food.
Some carbohydrate digestion begins.
Tongue pushes food to the back of the mouth
to start swallowing reflex.
Food passes through the esophagus and
enters stomach.
Stomach
Distended pouch. Strong circular muscles at
each end control food entering and leaving.
Mixes food by muscular contractions causing
food to break up further.
Secretes hydrochloric acid:
Begins protein digestion.
Kills microorganisms in food.
Nutrients not absorbed except water and
alcohol.
Small Intestine
Most digestion and absorption occurs in small
intestine.
Bile released to emulsify (break up) fat.
Pancreatic enzymes released to digest
carbohydrates, proteins and fats.
Final digestive enzymes in intestinal lining
break down carbohydrates, proteins and fats
into absorbable units.
Final Digestion Products
Final digestion products absorbed by cells
lining small intestine.
Carbohydrates:
Monosaccharides
Proteins:
Amino acids
Chains of 2 or 3 amino acids
Fats:
Fatty acids
Glycerol
Monoglycerides
Vitamins, minerals, water and some larger fat-like
compounds such as cholesterol are not broken
down before they are absorbed.
Absorption
Water-soluble nutrients and short fatty acids
released directly into the bloodstream.
Longer fatty acids, fat-soluble vitamins, and
fat-like compounds such as cholesterol are
not water-soluble.
Triglycerides reform in intestinal wall.
Packaged into a chylomicron and released into
lymphatic system.
Indigestible Matter
After digestion and absorption of nutrients,
indigestible matter, such as fiber moves into
the large intestine.
Indigestible matter is compacted by removing
water.
Little nutrient absorption occurs in large
intestine.
Metabolism
Chemical reactions that occur in the body:
Building and maintaining body tissues
Regulating body functions
Supplying energy
For metabolism to occur the body needs:
Water
Energy
Oxygen
Nutrients