Transcript Chapter 18: Nutrients and Digestion

 We need food to carry out our daily activities
 Does it matter what we eat??.....
 YES
 Our body needs a certain amount of nutrients
a day
 Nutrients are substances in food that provide
energy and materials for cell development,
growth and repair
 The body needs energy for every activity it
does, whether its voluntary or involuntary
 The amount of energy you need depends on
body mass, age and activity level
 Amount of energy in food is measured as
calories
 The number of calories varies depending of
the food that you are eating
4. Vitamins
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Are organic nutrients needed in small
quantities for growth, regulating body
functions and preventing some diseases
Most foods supply some vitamins, but no food
has them all
2 groups
Water Soluble
Need to be replenished daily
Fat Soluble
Stored in the body fat tissue
5. Minerals
 Inorganic (lack carbon)
 Your body uses 14 minerals
 Regulate chemical reactions in your body
 Build cells
 Send nerve impulses
 Carry oxygen to body cells
 Trace minerals are only needed by in small
amounts, like copper and iodine
 Table 1 pg 518
6. Water
 Is one of the most important factors for your
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survival
Can only live a few days without water
Other nutrients have to be dissolved in water
to be used
Human body is 60% water
2/3 of body water is located in your cells
Water leaves your body when you breathe,
sweat and you get rid of body wastes
 To replace water you need to drink 2L a day
 Water is also found in foods
 Water is important to cells because it aids in
chemical reactions
 Food is processed in four stages: ingestion,
digestion, absorption and elimination
 Digestion is the process that breaks down food
into small molecules so they can be absorbed
and moved into the blood
 2 types of digestion
1. Mechanical-food is chewed, mixed and
churned
2. Chemical- chemical reactions break down
food into small molecules
 Make chemical digestion possible
 Enzyme is a type of protein that speeds up the
rate of a chemical reaction
 They reduce the amount of energy needed for a
chemical reaction to begin
 Help you digest carbohydrates, proteins, and
fats
 Amylase helps speed up the break down of
complex carbohydrates (starch»sugar)
 Pepsin is found in the stomach and breaks
down proteins
 The pancreas releases enzymes into the
small intestine, which continue to break
down starches into glucose
 Also break down fats into fatty acids
 Enzymes also aid in the blood-clotting
process and in the process that builds your
body
 2 parts:
1. Digestive tract
 mouth, esophagus, stomach, small intestine,
large intestine, rectum and anus
2. Accessory organs
 (tongue, teeth, salivary gland, liver,
gallbladder and pancreas)
1. Mouth
 Mechanical and chemical digestion begin
 Mechanical digestion happens when you
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chew your food and mix it with your tongue
Chemical digestion happens when saliva is
mixed with your food
Ingestion is now over
Esophagus
Epiglottis covers your windpipe
About 25 cm long muscle
 Takes 4 to 7 s for food to move through the
esophagus into the stomach
 No digestion takes place
 Mucous glands keep the food moist
3. Stomach
 As food enters from the esophagus, the
stomach expands
 Food is digested both mechanically and
chemically
 Food is changed into chyme within 2-4 hours
 Little by little food moves into the small
intestine
4. Small Intestine
 Chyme leaves the stomach and enters the
duodenum, where most of the digestion
takes place
 Bile is released from your liver, and breaks up
the large fat particles
 Pancreas releases another solution that
breaks down carbohydrates, proteins and fats
 Pancreas also produces insulin, which always
glucose to pass from your bloodstream into
your cells
 The villi aids in the absorption of food
 Peristalsis forces the undigested food into your
large intestine
5. Large Intestine
 It’s main job is to absorb the water from the
undigested food
 This helps maintain homeostasis
 Chyme can stay in here for as long as 3 days
 Wastes are released by your rectum and anus
 Help break down intestinal material to make
vitamins
 Produce Vitamin K, which is needed for
blood clotting
 Make 2 B vitamins, niacin and thiamine,
which are important to you nervous system