Digestion and Human Nutrition

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Digestion and Human Nutrition

• Starr/Taggarts
• Biology
• The Unity and Diversity of Life, 9e
• Chapter 42
• And Other References

2
Key Concepts

• Interactions among systems supply cells with
  materials and dispose of wastes
• Most digestive systems have regions for
  transport, processing, and storage
• Energy intake must balance energy output by way
  of metabolic activity and physical exertion
• Nutrition involved the intake of foods, vitamins,
  and minerals

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Tasks Involved in Complete Digestive Systems

• Mechanical processing and motility
• Secretion of enzymes
• Digestion
• Absorption
• Elimination

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food, water intake
oxygen intake
DIGESTIVE SYSTEM
RESPIRATORY SYSTEM
elimination of carbon dioxide
nutrients, water, salts
oxygen
carbon dioxide
CIRCULATORY SYSTEM
URINARY SYSTEM
water solutes
elimination of food residues
rapid transport to and from all living cells
elimination of excess water salts, wastes
Fig. 42.2, p. 729
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Human Digestive System
6
taste bud
sensory receptor
Fig. 42.8, p. 733
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Fig. 42.13, p. 739
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Pathway of Food in the Body
Mouth gt Labial Cavity gt Teeth gt Buccal
Cavity gt Oral pharynx gt Nasal Pharynx gt
Larygeopharynx gt Respiratory Digestive Chiasm
gt Esophagus gt Stomach gt Small Intestine
gt Large Intestine gt Anus \gt Veriniform
Appendix
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Human Teeth
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The Stomach

• Mix food
• Protein digestion
• Controls passage of food
• Gastric fluid
• HCl Pepsin Mucus Chyme

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The Stomach

• The three parts of the stomach
• Cardiac near the heart
• Fundus bulk of stomach
• Pylorus lower stomach

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Fig. 42.10a, p. 736
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The Small Intestine

• 3 regions
• Duodenum - next to the stomach
• Most of digestion
• Receives secretions from
• Pancreas, liver and gallbladder
• Jejunum bulk of the small intestine
• Ileum next to the large intestine

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INTESTINAL LUMEN
bile salts

MICELLES
carbohydrates
monosaccharides
EMULSIFICATION DROPLETS
FAT GLOBULES (triglycerides)
free fatty acids, monoglycerides
proteins
amino acids
EPITHELIAL CELL
CHYLOMICRONS
INTERNAL ENVIRONMENT
Fig. 42.11, p. 737
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Bile and Fat Digestion

• Secreted by liver
• Salts, cholesterol, lecithin, pigments
• Stored in gallbladder
• Function
• Emulsification of fats

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Controls Over Digestion

• Nervous and Endocrine Systems
• Stretch reflex pathways
• Hormonal control
• Gastrin
• Secretin
• Cholecystokinin (CCK)
• Gastric Insulinotropic peptide (GIP)

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Absorption in the Small Intestine

• Main absorption site
• Large folds
• Villi Microvilli
• Passive and active transport
• Micelle formation of fats
• Movement of substances
• Peristalsis
• Segmentation

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Pathways of Organic Metabolism
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The Large Intestine

• Colon
• Continued absorption of ions and water
• Appendix
• Conditions
• Appendicitis
• Constipation
• Diarrhea
• Cancer

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Human Nutritional Requirements

• Food Pyramid
• Carbohydrates
• Energy
• Protein
• Building, repair, structures
• Fats
• Insulation, some vitamins, linoleic acid
• Caloric intake must equal expenditure to maintain
  body weight

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Fig. 42.15, p. 741
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Vitamins and Minerals

• Vitamins
• Fat Soluble
• A, D, E, K
• Water Soluble
• B1, B2, Niacin, B6, Folate, Pantothenic acid,
  B12, Biotin, C

• Minerals
• Calcium, Chloride, Copper, Fluoride, Iodine,
  Iron, Magnesium, Zinc, Phosphates, Potassium,
  Sodium, Sulfur

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Weight Guidelines for Women
Weight Guidelines for Men
Starting with an ideal weight of 100 pounds for a
woman who is 5 feet tall, add five additional
pounds for each additional inch of height.
Examples
Starting with an ideal weight of 106 pounds for a
man who is 5 feet tall, add six additional pounds
for each additional inch of height. Examples
Fig. 42.16, p. 744
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In Conclusion

• Nutrition refers to the processes of digestion,
  absorption, and the use of food by the body
• A complete digestive system involves a tube that
  connects mouth to anus as well as specialized
  regions
• Mechanical and chemical processing of foods
  begins in the mouth and continues throughout
  certain structures

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In Conclusion

• Secretions, digestion, absorption, and
  elimination are all processes that proceed in the
  digestive system
• Digestion is completed and most nutrients are
  absorbed in the small intestine
• The pancreas secretes the main digestive enzymes
  whereas bile emulsifies fats

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In Conclusion

• Substances are absorbed by diffusion, and passive
  and active transport mechanisms
• The nervous and endocrine system regulates
  digestive activity
• Nutritionists advise intake of foods in certain
  proportions for energy, building, repair and
  maintenance
• developed by M. Roig