Digestive System and Nutrition
Organs
Process of Digestion
Nutrition
Path of Food through the Digestive System
mouth
pharynx
esophagus
Produces
peptidases,
maltase,
lactase
Produces
pepsin, HCl
stomach
small
intestine
large
intestine
anal canal
Peristalsis: Muscular contractions that move food through the digestive system
Accessory Organs and Glands
Produce
salivary
amylase
salivary
glands
Produces
bile
Produces
pancreatic
amylase,
trypsin,
lipase
liver
gall
bladder
Stores bile
pancreas
Process of Digestion and Absorption
• Mouth
– Teeth chew food into
smaller pieces
– Salivary amylase
(enzyme in saliva)
begins starch
digestion
– Tongue mixes food
with saliva to form Starch in bun has
been broken into
bolus to be
smaller chains of
swallowed
sugars
Process of Digestion and Absorption
• Stomach
– HCl acid unfolds
proteins
– Pepsin (enzyme)
begins protein
digestion, breaking
some peptide bonds
esophagus
sphincter
muscularis
layer has
three layers
of muscle
pyloric
sphincter
mucosa layer
has rugae
gastric pit
gastric gland
Protein in beef has
been broken into
smaller chains of
amino acids
cells that
secrete
gastric
juice
Contains pepsin,
HCl, mucus
Process of Digestion and Absorption
• Small Intestine
villus
– Large surface area due
to numerous villi
– Bile emulsifies lipids
– Pancreatic and intestinal
enzymes digest
carbohydrates, lipids,
venule
proteins
– Amino acids and sugars
arteriole lymphatic
absorbed into blood
vessel
– Lipids absorbed into Carbohydrate,
Protein and Fat
lymphatic system
have been digested
and absorbed
lacteal
blood
capillaries
Digestion occurs by Hydrolysis of Macromolecules
Emulsification: physical
dispersion of lipids into
smaller droplets
carbohydrate
pancreatic amylase
Hydrolysis:
chemical
separation of
subunits
maltase
cell of
intestinal
villus
protein
+
bile salts fat globules
trypsin
emulsification
droplets
peptides
hydrolysis
peptidase
lipase
Hydrolysis
glucose
amino acids
pH = basic
pH = basic
pH = basic
blood capillary
Carbohydrate digestion
blood capillary
Protein digestion
lymphatic
capillary
Fat digestion
Process of Digestion and Absorption
• Large Intestine
– Absorbs water
– Absorbs salts (minerals)
– Absorbs some vitamins
– Stores waste for later
elimination
Calcium from
cheese has been
absorbed. Fiber
from tomatoes and
lettuce remains.
Distribution and Use of Nutrients
• Liver
– regulates nutrient entry into
blood
– detoxifies blood
– stores iron and fat-soluble
vitamins
– makes plasma proteins
– stores and releases glucose
– produces urea from amino acids
– produces bile
– destroys old red blood cells
– helps regulate blood cholesterol
Applying Your Knowledge
1.
2.
3.
4.
A.
B.
C.
D.
Stomach
Mouth
Large Intestine
Small Intestine
Where are fats digested?
Where do proteins unfold?
Where does starch digestion begin?
Where is water absorbed?
Nutritional Recommendations
• Macronutrients
– Carbohydrate
– Fat
– Protein
• Water
• Micronutrients
– Vitamins
– Minerals
Use fats in small amounts
June 2011 Recommendations
Balancing Calories
• Enjoy your food, but eat less.
• Avoid oversized portions.
Foods to Increase
• Make half your plate fruits and
vegetables.
• Make at least half your grains
whole grains.
• Switch to fat-free or low-fat
(1%) milk.
Foods to Reduce
• Compare sodium in foods like
soup, bread, and frozen meals,
and choose the foods with
lower numbers.
• Drink water instead of sugary
drinks.
Carbohydrates: Dietary
Recommendations
• 58% of calories from carbohydrates
• No more than 10% of calories from simple,
refined sugars
• Emphasize
– Complex Carbohydrates
• Starch
• Fiber (cellulose)
– Naturally-occurring simple carbohydrates
• Fructose from fruit
• Lactose from milk
Fats: Dietary Recommendations
•
•
•
•
< 30% of calories from fats
< 10% of calories from saturated fats
Limit cholesterol to 300 mg/day
Avoid “trans” fatty acids in partially
hydrogenated products
• Emphasize
– Unsaturated fatty acids from
vegetables, fish, legumes, and nuts
– Oils: mono- or polyunsaturated
Proteins: Dietary
Recommendations
• 12% of calories from proteins
• 8 essential amino acids obtained
from
–Lean sources of animal protein
–Complementary plant proteins
• Beans + Grains
• Beans + Seeds
Vitamins
• Organic compounds used in metabolic
reactions as coenzymes or
antioxidants
• Water Soluble: B vitamins, C
• Fat Soluble: A, D, E, K
• Adequate amounts come from a varied
diet that includes vegetables and fruits
• May prevent cancer and cardiovascular
disease
Minerals
• Inorganic substances required by the
body
• Macrominerals needed in large
amounts, eg. calcium
• Microminerals needed in smaller
amounts, eg. iron
• May need to emphasize certain foods
to obtain iron or calcium
• May need to limit foods high in sodium
Applying Your Knowledge
1.
2.
3.
4.
5.
Calcium
Vitamin C
Lipid
Carbohydrate
Protein
A. Which one is a mineral?
B. Which macronutrient should supply the
greatest number of calories in the diet?
C. Which one may protect against cancer?
Reading a
Nutrition Label
More info at
http://www.fda.gov
Calorie Percentage Calculations
Number of grams
Caloric value
12 x 9/250 = 0.432 x 100 = 43.2%
3 x 9/250 = 0.108 x 100 = 10.8%
31 x 4/250 = 0.496 x 100 = 49.6%
5 x 4/250 = 0.080 x 100 = 8.0%
5 x 4/250 = 0.080 x 100 = 8.0%
These should add to 100%.
Total calories