Human Nutrition

1. Human Nutrition

2. L.L. List as many parts of the human digestive system as you can recall, and put them in their correct order. List accessory organs separately.

3. Why do we need nutrients? • For energy, growth, repair, body functions, and regulation • Food must be digestible, absorbable, and useable for metabolism. • We require roughage (fiber) to help remove indigestible materials.

4. How many kinds of nutrients are there? • 1. Carbohydrates • 2. Lipids • 3. Proteins • 4. Minerals • 5. Vitamins • 6. Water

5. How many of these nutrients do we need? • The amount varies with sex, age, and physical activity * Energy in food is measured in calories. A food calorie is the amount of heat energy needed to raise 1Kg of water 1 degree Celsius.

6. How are these nutrients used? There are 3 categories: 1. Carbohydrates: (examples: _______) • Main source of energy (50% of daily energy needs) • Main source of roughage (fruits and vegetables) • Excess carbohydrates are stored as glycogen.

7. Lipids • Get more energy in smaller amount • Stored as fat when in excess • Needed by body for cell membrane structure, organ cushioning and insulation • Should not have more than 30% of your daily intake of calories • Saturated and unsaturated

8. 3. Proteins • Provides AA’s (amino acids) from which the body synthesizes all needed proteins (enzymes and proteins) • Provide materials needed for tissue growth and repair • Recommended amounts: male 56g 46g • 20 AA body requires, 8 of which can be called essential AA’s

9. Proteins (cont.) • For protein synthesis to occur all AA’s need to be present because they can’t store them. Missing any causes a stop in synthesis and all AA present to be deaminated (broken down) • Complete vs. incomplete protein foods

10. Functions of Organs &Structure of the Alimentary Canal • Mouth/Pharynx- -site of partial chemical digestion (enzymes in saliva) of carbohydrates (polysac->disac) -site of mechanical digestion (mastication) -BOLUS forms here

11. Epiglottis - covers opening of trachea when bolus or liquid is swallowed.

12. Esophagus -Peristalsis- initiated here

13. Cardiac Sphincter -food enters stomach through this (acts as a valve) -vomiting/heartburn (reverse peristalsis)

15. Stomach -site of mechanical digestion -site of chemical digestion of proteins (gastric protease) -HCl kills bacteria (pH 1.5-2.5)

16. Stomach (cont.) • Food-liquids become chyme • Stomach can EXPAND to hold 2 LITERS!! • OUTSTANDING!!!!!!!!!!!!!!!!!!!!! • Mucus gets secreted from glands and protects the stomach lining from destruction via ulcers

17. Rugae- folds in the stomach lining that allow it to expand with more food How do we vomit? http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion Rugae in the Stomach

18. Pyloric Sphincter • Pyloric Sphincter-food enters small intestine through this

19. Small Intestine • Primary site of chemical digestion of carbs, fats and proteins • Site of absorption of end products through intestinal wall- long folds are lined with villi which increase the surface area • Monosaccharide, AA and di-peptides get quickly absorbed • Alkaline environment (aided by pancreas and bile)

20. Pancreas • Looks like a salivary gland or in my opinion a grape cluster • Pancreatic duct delivers enzymes, etc. to aid in digestion • Islets of Langerhans: producers of insulin

21. Liver (many jobs) • Makes bile, prothrombin (used for clotting) • Breaks down toxic substances (alcohol, drugs, etc.) • Important in regulation • Removes NH2 from AA making urea • Stores vitamins A, D, E, and minerals • Regulates blood glucose

22. What is bile? • Emulsifies fats, aids in neutralizing intestines • Its chief pigment is bilirubin (if this pigment increases in body due to liver dysfunction) eyes->yellow… etc.

23. Transverse Colon: right to left Ascending Colon: Descending Colon: up the right side down the left side Cecum: sac on Sigmoid Colon: lower right side S-shaped Anatomy of the Large Intestine

24. Large Intestine: • Water absorption • E. coli present • Aid in synthesis of AA and vitamins • Chief source of vitamin K (byproduct)

25. Rectum: • Storage and elimination of undigested materials (feces get its “normal” color from breakdown of HgB in liver which is egested)

26. Functions of the Digestive System • Ingestion: intake of nutrients • Digestion: breakdown of large particles into smaller ones • Absorption: uptake of nutrient molecules • Defecation: elimination of undigested residues

27. Stages of Digestion • Mechanical: physical breakdown of food • Chemical: digestive enzymes hydrolyze food particles to break larger molecules into smaller ones • Some nutrients are absorbed with out digestion • Vitamins, minerals, cholesterol, water

28. Enzymes Involved in Chemical Digestion • Saliva: • Amylase: breaks down starch • Lipase: breaks down fats when it enters the stomach • Low pH of the stomach activates the enzyme

29. Enzymes Involved in Chemical Digestion • Stomach: • Digestive chemicals- • HCL: activates enzymes, breaks up foods, kills bacteria • Pepsin: digests proteins • Renin: digests milk • Gastric protease: breaks down proteins

30. Enzymes Involved in Chemical Digestion in the Small Intestine • Liver secretes bile that is active in the small intestine • Bile: aids in fat digestion and absorption • Activates pancreatic enzymes • Synthesized from cholesterol • Bacteria in the small intestine use bilirubin to make your feces brown • Gall bladder stores and concentrates bile

31. Enzymes Involved in Chemical Digestion in the Small Intestine • Pancreas: secretes pancreatic juice • Amylase: breaks down starch • Lipase: breaks down fats • Trypsin: breaks down proteins

33. Final Destinations of Digestion Products • Starches  bloodstream • Fats  lymph vessels (lacteals) • Proteins  bloodstream • Unusable materials are egested( defecated) through the large intestine to colon to anus