Transcript Unit 7: The Digestive Tract

Unit 7: The Digestive Tract
From the Liver: Bile
fluid containing water, electrolytes and a battery of
organic molecules including bile acids, cholesterol,
phospholipids and bilirubin :
• contains bile acids, which are critical for
digestion and absorption of fats and fat-soluble
vitamins in the small intestine.
•Many waste products are eliminated from the
body by secretion into bile and elimination in
feces.
From the pancreas:
• Bicarbonate is released to quickly neutralize
acid from the stomach
• Many enzymes are released to break down
proteins, fats and starches.
Macromolecules are broken down
Polysaccharides:
Starch, cellulose & glycogen
consist of linked glucose molecules
Triglycerides
• most abundant storage
form of fat in animals or
plants
• most important lipid
• composed of a molecule
of glycerol linked to three
fatty acid molecules
• must be broken down by
digestion to be absorbed
Cross-section of Digestive Tract
Blood & Lymph
Lymphatic System
Blood Vessels
•Arteries and
veins
infiltrate
villi.
•Arteries pick
up nutrients
•Veins take
away wastes.
•Vessels
infiltrate
villi.
•Lymphatic
fluid has
substances
to bind fat
and carry
it to blood
stream.
Blood from the Small Intestine goes
to the Liver first
Stomach Transit Time Varies
Digestive Transit Time
How long does it take?
Digestion and Absorption
• Over 90% of the protein, fat, & carbohydrate
we consume is digested and absorbed.
• Dietary fiber leaves digestive system in same
form as it entered.
• Humans have no enzymes to break down
fiber.
• Some fiber is digested in the large intestine by
bacteria.
Digestive Disorders:
common problems
• Heartburn, hemorrhoids, irritable bowel syndrome,
and duodenal and stomach ulcers are leading causes
of hospitalization among U.S. and Canadian adults
aged 20-44 years.
• Digestive disorders are common in children as well as
adults.
• At least one-third of U.S. adults experience
heartburn
• About 30% of school children experience
constipation.
Lactose Maldigestion
• Caused by genetically determined low
production of enzyme that digests lactose.
• After consuming milk  free lactose in large
intestine
• Symptoms: bloated feeling
• diarrhea due to fluid accumulation,
• gas and abdominal cramping
Low Lactose and Calcium Rich Foods
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• Dairy Ease Milk and Lactaid Milk
Buttermilk, Yogurt, Kefir
Cheeses, ice cream (lower than sherbet)
Fortified soy milk
Orange juice fortified with calcium
Often chocolate milk or small amounts of milk with
solid food is tolerated well.
• Lactaid pills or drops. Calcium pills with Vit D