1. Digestion

2. Journey of a cheeseburger

3. What is digestion?
Digestion is the mechanical and chemical breakdown of food into usable molecules
The Alimentary Canal (GI Tract) extends from the mouth to the anus with acessory organs (liver and pancreas)
It is a 9 meter long tube
Your entire body can be thought of as a tube within a tube.
Movement through the tube is by wavelike motion called peristalsis

4. Peristalsis
(The British spelling of esophagus is “oesophagus”)

5. Major Parts and Function of the Digestive System:
Mouth
Teeth begin digestion mechanically
Chewing (“mastication”) breaks apart food
2 sets of teeth
Primary or “baby teeth” (20 in all)
Permanent teeth (32 in all)
Incisors for cutting
Canines “fangs” for tearing
Premolars and molars for grinding
Tooth has a crown and a root
Pulp contains the nerve and blood supply for nutrients and waste removal

6. Tooth Diagram

7. Digestive System
Saliva - begins chemical digestion of carbohydrates & secrete amaylase (digestive enzyme)
Tongue - Pushes food back towards throat
Palate (hard and soft) - roof of oral cavity
Palatine tonsils - lymphatic tissue
Pharyngeal tonsils (adenoids) - lymphatic
Pharynx - connects nasal and oral cavities

8. Digestive system
Esophagus - food passageway (heartburn is caused by the effects of gastric juice on the esophagus)
Stomach - secretes gastric juices (pepsin, hydrochloric acid) which digest proteins and creates a paste of food called chyme.
Pancreas - secretes pancreatic juice which helps digest carbs, fats, and nucleic acids and proteins.

9. Digestive system functions:
Liver has many functions. The major are:
production of bile, which helps carry away waste and break down fats in the small intestine during digestion
production of certain proteins for blood plasma
production of cholesterol and special proteins to help carry fats through the body
conversion of excess glucose into glycogen for storage (This glycogen can later be converted back to glucose for energy.)

10. Digestive system functions:
Liver functions (continued):
regulation of blood levels of amino acids, which form the building blocks of proteins
processing of hemoglobin for use of its iron content (The liver stores iron.)
conversion of poisonous ammonia to urea (Urea is one of the end products of protein metabolism that is excreted in the urine.)
clearing the blood of drugs and other poisonous substances

11. Digestive system functions:
Liver functions (continued):
regulating blood clotting
resisting infections by producing immune factors and removing bacteria from the blood stream
stores vitamin D
Gall Bladder
Stores bile, releases through bile duct
Bile in the gall bladder can precipitate and form solids or “stones”

12. Digestive System functions
Small Intestine
Receives secretions from pancreas and liver,completes digestion of nutrients in chyme, absorbs products of digestion through fingerlike projections called villi; transports residues to large intestine
3 major sections
Duodenum
Jejunum
Ileum
Connected by mesentery which suspends these portions from abdominal wall

13. Digestive System Components
Large Intestine
Absorbs water and electrolytes from chyme, forms and stores feces
Cecum = beginning of large intestine
Appendix - small closed part, no longer serves a digestive function, but contains lymphatic tissue
Colon - 4 sections
Ascending colon, begins at cecum
Transverse colon
Descending colon
Sigmoid colon

14. Digestive System Rectum Anus Last part of large intestine
Expels waste - two sphincter muscles guard the anus (one under involuntary control ,the other, and final one, is under voluntary control)

15. Nutrients 4 major nutrients
Carbohydrates - supply energy (1 calorie per gram)
Lipids - supply energy for cellular processes and for building cells, stores energy (9 calories per gram)
Proteins - control metabolic rates, clotting factors, keratin of skin and hair, source of energy (1 calorie per gram)

16. Vitamins
Organic compounds required in small amounts for normal metabolic processes. Must come from foods.
Vitamins A,C,D, and E appear to have anticancer effects. Most vitamins function as coenzymes to help an enzyme accomplish a function
Fat soluble - A,D,E,K
Water-Soluble - Thiamin, Riboflavin, C, Niacin, B6, Folate, B12, Biotin, Pantothenic acid

17. Vitamins A for healthy eyes, skin, bones and hormone synthesis
C for collagen, detoxification
Folate needed for DNA and RNA metabolism
Niacin, Biotin, Thiamin needed for energy metabolism

18. Minerals Concentrated in bones and teeth
Major minerals are calcium and phosphorous
The body needs 7 - potassium, sulfur, sodium, chloride and magnesium in addition to trace amounts
Fats and sugars have few minerals.

19. Minerals Phosphorus needed for bone and tooth formation
Magnesium needed for bone, tooth, and enzyme formation
Sulfur needed for cartilage, tendon, and proteins
Sodium needed for nerve impulse transmission
Potassium - nerve function
Chloride - gastric juices and electrolyte balance

20. More Minerals Iron - for hemoglobin Iodine for thyroid function
Fluoride - for bones and teeth
Zinc for insulin, sperm production
Selenium is an antioxidant
Copper helps produce hemoglobin
Chromium for energy metabolism
Manganese and molybdenum are components of enzymes