Chapter 18: Nutrients and Digestion

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Chapter 18 Nutrients and Digestion
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Aim Why do you eat?
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• 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

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• 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

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Aim What are the classes of nutrients?
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• Vitamins
• 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

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• 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

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• Water
• Is one of the most important factors for your
  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

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• 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

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Aim What are the functions of the digestive
system?
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Functions of the Digestive System

• 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
• Mechanical-food is chewed, mixed and churned
• Chemical- chemical reactions break down food into
  small molecules

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Enzymes

• 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 (starchsugar)

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• 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

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Aim What role do the organs of the digestive
system play?
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Digestive System

• 2 parts
• Digestive tract
• mouth, esophagus, stomach, small intestine, large
  intestine, rectum and anus
• Accessory organs
• (tongue, teeth, salivary gland, liver,
  gallbladder and pancreas)

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• Mouth
• Mechanical and chemical digestion begin
• Mechanical digestion happens when you 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

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• 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
• 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

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• 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

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• The villi aids in the absorption of food
• Peristalsis forces the undigested food into your
  large intestine
• Large Intestine
• Its 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

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Bacteria

• 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