Transcript DIGESTIVE SYSTEM

DIGESTIVE SYSTEM
Function:
Digestion, absorption and
eliminate waste.
Changing food so that they can
be absorbed and used by cells.
Type of Digestion
1.
Mechanical digestion
Chewing, swallowing, peristalsis etc. break
food into tiny particles, mix them well with
the digestive juices and move them along
the digestive tract.
2.
Chemical digestion
Breaks down large food molecules into
smaller molecular by digestive enzymes.
Reference:
http://www.amaassn.org/ama/pub/category/715
5.html
Digestion processes:
Mouth (mechanical and chemical digestion – teeth
and salivary gland)
esophagus (mechanical peristalsis)
stomach (chemical enzyme)
small intestine (chemical enzyme)
bile
gallbladder
pancreatic juice
large intestine
liver
pancreas
Digestive juices and enzymes
Enzyme digests
Resulting products
Saliva (accessory)
Amylase (ptyalin)
Starch
Maltose
Stomach (main)
Gastric juice
Pepsin (protease)
Hydrochloric acid
Lipase
Protein
Fat
(not significant)
Polypeptides
Fatty acid
Glycerol
Liver and gallbladder (accessory)
Bile
Emulsified large
fat droplets
Small fat droplets
Pancreatic juice (accessory)
Protease (trypsin)
Lipase
Amylase
Protein
Bile emulsified fat
Starch
Amino acid (A.A.), peptide
Fatty acid and glycerol
Maltose
Small intestine (main)
Intestinal juice
Peptidase
Sucrase
Lactase
Maltase
Peptide
Sucrose
Lactose
Maltose
Amino acid (A.A.)
monosaccharide
Food
Food is used as collections of nutrients in a
form which is eaten, digested and metabolized
to provide energy and materials that build and
maintain the structure, regulate the function
of the body.
Major nutritional sources:
1.
2.
3.
Organic compounds – carbohydrates
proteins
lipids
vitamins
Inorganic compound – water H2O
Minerals: Na, K, P, S, Ca, Fe… etc.
Energy balance:
30~40% of energy are used for normal growth,
development and activity. The rest is used for
maintain body temperature.
Food and Nutrition Board recommend:
female: 2,000 Kcal
male:2,700 Kcal
1Kcal: energy required to raise the temperature of 1 liter
of H2O from 15~16°C
Energy producing food:
protein:
4 Kcal/g
carbohydrate
4 Kcal/g
fat
9 Kcal/g
1. Organic Compounds
A. Carbohydrate
suggest intake: 50~100 g/day
primary energy source
eg. Sugar, starch
B. Lipid
60~90 g/day
fat containing compounds
fat soluble vitamins: A, D, E, K
Vitamin A: vision, bone, teeth, anticancer

Vitamin D: control optimal blood level of Ca, P

Vitamin E: antioxidant agent

Vitamin K: blood clot
Essential fat (lipid): linoleic acid

C.
Proteins
40~60 g/day, but in USA about 100 g/day

Essential amino acid:
eg. Lysine, leucine, isoleucine and tryptophan
Complete proteins from animal sources
Incomplete proteins from plants
eg. Peas and beans are good lysine source but low in
trptophan; nuts, seeds and cereals are good source in
tryptophan but low in lysine
Complementary diet is important for vegetarians
Body Mass Index (BMI)
Weight (lbs) x 704
(Height in inches)2
= BMI
BMI of 25 is ideal
Less than 25 is great
30 and above is very unhealthy