1. health and fitness
2. disease
3. cholesterol

Digestive system and
Nutrition
WHAT IS DIGESTION?
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HOW DOES YOUR BODY
ABSORB NUTRIENTS?
!
WHAT DO WE KNOW ABOUT
THE DIGESTIVE SYSTEM?
!
-the digestive system functions to break down the
macromolecules found in your diet into usable
forms for the body
!
-products of digestion are used for energy,
building blocks, and as enzymes and/or
coenzymes
Secretion
Site of production
Function
saliva
mouth
contributes to starch digestion via salivary
amylase; lubricates the inside of the mouth to
assist in swallowing
mucus
mouth, stomach, small
intestine, and large intestine
protects the cells lining the innermost portion of
the digestive tract; lubricates food as it travels
through the digestive tract
enzymes
mouth, stomach, small
intestine, and pancreas
promote digestion of food masses into particles
small enough for absorption into the
bloodstream
acid
stomach
promotes digestion of protein
bile
liver (stored in gall bladder)
suspends fat in water, using bile salts,
cholesterol, and lecithin to aid digestion of fats in
small intestine
bicarbonate
pancreas and small intestine
neutralizes stomach acid when it reaches the
small intestine
hormones
stomach, small intestine, and stimulate production and/or release of acid,
pancreas
enzymes, bile, and bicarbonate; help to regulate
peristalsis
Anatomy of the digestive system:
Alimentary Canal
Accessory Digestive Organs
ingests
teeth
digests
tongue
absorbs
large digestive glands
defecates
liver
gallbladder
pancreas
Alimentary Canal (GI tract)
mouth: mechanical breakdown of food, begins chemical
pharynx: connects mouth with the esophagus
esophagus: peristalsis pushes food to the stomach
stomach: secretes acids and enzymes to begin digestion
of proteins
small intestine: mixes food with bile and pancreatic fluid,
main site of nutrient absorption
large intestine: absorbs water and electrolytes to form
feces
Rectum:regulates emission of feces
Anus: exit vent
Accessory organs:
salivary glands: secrete saliva which contains enzymes
that initiate breakdown of carbs
!
Liver: produces bile which emulsifies fats
!
Gallbladder: Stores bile and secretes it into the the
small intestine
!
Pancreas: Produces and secretes pancreatic fluids
into the small intestine
Layers of the alimentary canal
Lumen: the cavity (not a layer)
Inner-most layer is the mucosal layer(secretes mucous and
absorbs nutrients from ingested material)
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submucosa: blood vessels, glands, vessels move nutrients to
other parts of the body.
Muscular layer: contracts and releases to move food
Serosa: outer covering, secretes fluid to keep layer moist
and lubricated so all organs slide freely against each other.
Mouth (pg 404)
Uvula
Epiglottis
oral cavity
tongue
Nasal cavity
pharynx
Soft and Hard Palate
Hyoid
Lingual Frenulum
Naso, oro, laryngo
Salivary glands
Pharynx and Esophagus (pg410)
Read about swallowing mechanism
straight
collapsible tube
about 25 cm long
passageway for
food
Movement is caused
by
Peristalsis
Stomach
pyloric sphincter
Gastric secretions
Food and acids=
Chyme
Stomach
Stomach is for digestion
Only chemicals absorbed by the stomach are aspirin and
alcohol
Contains pepsin: a protein digesting enzyme
Hydrochloric acid: activates pepsin, prevents microbial
growth
Mucous prevents acid from digesting stomach lining
!
Pancreas
Pancreatic juice:
proteolytic enzymes
lipase
Liver
Can weigh 3 lbs
-role in carbohydrate metabolism by maintaining normal
glucose levels in the blood.
-oxidizes fatty acids
-protein metabolism
-makes urea
-converts amino acids to other amino acids
-stores vitamin A, D and B12, Iron, glycogen
-destroys damaged red blood cells
-Main function pertaining to digestion is Bile production
4 Lobes
!
Right, Left,
Quadrate, caudate
What is Bile?
water, bile salts, bile pigments, cholesterol, electrolytes
So what is bile?
a bitter greenish-brown alkaline fluid that aids
digestion and is secreted by the liver and stored in
the gallbladder
Gallbladder
-Pear shaped sac near the liver
-stores bile and concentrates bile
-Gallstones are cholesterol that have precipitated out of
solution.
SOOOO
The Liver, Gallbladder and Pancreas all secrete
enzymes, and fluids to aid in the breakdown of
ingested food. But each has its own important
function
Liver: Makes bile, oxidizes fatty acids,
Gallbladder: stores bile
Pancreas:pancreatic juices, proteolytic enzymes
-Chyme is pushed into the duodenum of the small intestine
where most digestion occurs.
!
-Moves on to the jejunum then the ileum where absorption
occurs. 90% absorption takes place in the small intestine.
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-accessory organs secrete juices to aid in digestion
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- villi are finger-like structures that create greater surface
area
Lacteal: lymphatic capillary that absorbs fat, eventually
empties into the bloodstream
Large intestine
Main functions: water absorption, houses bacteria,
produces feces.
xray swallowing
crash course
2 min video on digestion
bozeman Science