Digestion and Nutrition

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Digestion and Nutrition

• Chapter 30 (M)

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Food and Nutrients

• Food? Any substance, either raw or processed
  which is meant for human consumption
• Nutrients? The components of food that the body
  can use for growth, repair and energy

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How Nutrients are Obtained

• Heterotrophs get nutrients in various ways

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Types of Nutrients

• Carbohydrates
• Proteins
• Fats
• Vitamins
• Minerals
• Water

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Food as Fuel

• Carbohydrates, fats and proteins are all used to
  generate ATP
• Fats?9 Calories/gm, Proteins and Carbs?
  4Calories/gm
• 1 Calorie (kilocalorie) 1000 calories
• Basic Calorie need? 2200 for female teens, 2500
  males

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Essential nutrients

• Must be ingested, cell cant construct these
• Essential Fatty Acids? Linoleic Acid
• Essential Amino Acids? 8 AA
• Vitamins? water soluble (can be excreted) and fat
  soluble( excess might cause damages), reqd for
  enzyme function
• Minerals? reqd, but large amts can cause damage

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Nutrition and a Balanced Diet

• Balanced Diet? provides nutrients in adequate
  amounts and enough energy to maintain a healthful
  weight
• Balancing your diet
• Food labels
• Food guide pyramid

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The Food Guide Pyramid
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The Food Guide Pyramid

• Number of calories depends on
• Age
• Sex
• Size
• Whether or not you are a pregnant or
  breastfeeding woman
• Whether you have a chronic illness
• The National Academy of Sciences recommends the
  following calorie categories
• 1,600 calories - Many sedentary women and some
  older adults
• 2,200 calories - Children, teenage girls, active
  women and many sedentary men.
• Women who are pregnant may need around 500
  calories more per day and an additional 300
  calories for breast-feeding
• 2,800 calories - Teenage boys, active men and
  very active women
• The Food Guide Pyramid can be extremely useful -
  whether you want to gain weight, lose weight or
  maintain your weight. Eating a healthy diet is a
  little easier if you base your choices on the
  Food Pyramid.

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MyPyramid ? USDA's newest food pyramid guide

•  Encourages consumers to make healthier food
  choices
• To get regular exercise 
• Food groups are arranged in vertically bands,
  instead of horizontal ones
• Band width indicates portion size
• The wider the band, the more food from that group
  should be eaten.

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The Digestive System

• Converts food into small molecules that can be
  used by all cells of the body
• Food is processed in four phases by the digestive
  system

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Stages of Food Processing

• Ingestion eating or drinking
• Digestion Breaking food into smaller molecules
• Mechanical
• Chemical (Enzymes)
• Absorption nutrient molecules enter blood, the
  circulatory system transports it through out the
  body
• Elimination undigested material passes out of
  the body

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The Digestive System

• Functions like a series of tube like organs which
  pass through the body from the mouth to the anus?
  Alimentary Canal
• Alimentary Canal? can be about 30 long
• Accessory organs? Pancreas, Liver, Gallbladder?
  secrete enzymes that are released into the food
  tube

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Digestion in the Mouth
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It all begins in the mouth . . .

• Teeth, tongue
• Salivary glands
• Mucus
• Amylase
• Only carbohydrates are digested here

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SWALLOWING AND PERISTALSIS
GLOTTIS AND EPIGLOTTIS
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Peristalsis

• Rhythmic muscular contractions propel a bolus of
  food

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The human digestive system
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Digestion in the Stomach

• Muscular organ
• Acts as a reservoir where food is prepared for
  digestion in the SI
• Produces Gastric Juices

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Stomach Functions

• Food Storage
• Mechanical Digestion
• Chemical Digestion
• Secretions
• Mucus
• Enzyme?Pepsinogen
• HCL
• CHYME? semi-fluid food mixture leaves.

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Protection from Self-Digestion

• Protective lining
• Main enzyme -Pepsin is inactive Pepsinogen when
  secreted

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Digestion in the Stomach

• Pepsinogen ?Comes in contact with HCl? Pepsin
• Pepsin? converts proteins into peptones
• Acidity of Gastric juices ?kills some bacteria
  that enters with food
• Gastric Juices ? stimulated by psychological and
  chemical means
• Peristaltic process of moving chyme into the SI
  takes place for 6hrs

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Small Intestine

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Digestion in the Small Intestine

• Main stage of Digestion
• As chyme enters the SI secretes juices that are
  alkaline and neutralizes the acidity
• SI? maltase,lactase,sucrase? breaks disaccharides
• Liver secretes bile? emulsifies fats
• Dipeptidases ? dipeptides into AAs
• Pancreas
• Trypsin Chymotrypsin? break down proteins
• Amylase? converts starch into maltose
• Lipase? breaks fats
• Process is complete in about 4 hrs

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Pancreas

• Secretes
• Hormones
• Sodium bicarbonate
• Digestive enzymes
• Lipase
• Trypsinogen
• Amylase

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Liver

• Secretes
• Blood clotting enzymes
• Stores glycogen
• Bile
• Stored in gall bladder
• Emulsifies fat

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The structure of the Small Intestine
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LARGE INTESTINE COLON

• Anatomy
• Functions
• a. Reclaim water
• b. Synthesis of vitamins by E. coli
• Feces
• Rectum
• Anus
• Diarrhea
• Constipation

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Can you name the parts and tell what they do?