1. Digestive System
pp. 183 to 190

2. Digestive System

3. Digestive tract is one, long, thin, muscular tube
All parts of the “tube” are lined with muscle!
Why might this be important? (Think about how muscle tissue behaves...)
So it can stretch to accommodate food moving around.
All parts of the digestive tract are lined with mucus (some more than others)
Why might this be important?
So food slides down easily; and muscle is protected by mucus from stomach acid and enzymes.
The stomach is protected by the lower part of the ribcage?
To protect it from being punctured and stomach acid leaking into abdomen.

4. Oral Cavity & Salivary Glands
Teeth grind, hold, tear and chew
Tongue moves food, aids in swallowing = forms a bolus (ball of food)
Pharynx receives food (also air from nose)
Salivary glands-secrete saliva which contains amylase
(mechanical digestion)
(chemical digestion)
Carbohydrates (amylose) breaks down into maltose

5. 7 seconds for food to go down entire esophagus to stomach!
Muscular tube connecting mouth to stomach
Peristalsis (wave like contractions) push food down
(mechanical digestion)
7 seconds for food to go down entire esophagus to stomach!

6. Stomach Acidic environment (gastric juice)
Sphincters at start and end of stomach are muscles that control movement of food in/out of stomach
3 muscle layers contract to churn and mix food
Protein digestion begins
Mucus part of stomach lining = protects the stomach from gastric juices
Some absorption (water, alcohol and aspirin)
(chemical digestion)
(mechanical digestion)
(pepsin enzymes from gastric juices)

7. Small Intestines
7m - large surface area due to villi (finger like projections)
Duodenum (upper portion) site of digestion (including protein & carb digestion
(pepitidases for proteins  amino acids
(maltase for maltose  glucose)
Fat digestion starts here (aided by liver and pancreas)
Absorbs nutrients
Pancreatic juices from pancreas & bile from liver enter here
(chemical digestion)

8. Accessory Organs
Organs that are involved in digestion, but are not part of the continuous muscular tube of the digestive tract
Include:
Liver
Gall bladder
Pancreas
Does not directly digest food themselves… only contribute to the process!

9. Liver Secretes bile for fat digestion in intestines
“Emulsifier”  breaks fat down into small globules for further digestion
Stores carbs/vitamins & eliminates harmful substances

10. Gall Bladder Stores and concentrates bile
Releases bile into small intestine

11. Pancreas
Produces pancreatic juice contains enzymes to digest: carbs, proteins and fat
Makes bicarbonate to help acidity of stomach
Pancreas also part of Endocrine System
Pancreatic juices enter the small intestine at the duodenum
trypsin (long proteins  short proteins)
pancreatic amylase (starch  maltose)
lipase (fats  fatty acids)

12. Large Intestines (Colon)
1.5m long (colon)
Absorbs water (mostly), vitamins and minerals
Harmless bacteria (over 700 species!!) produce vitamin B & vitamin K (imp. for cell metabolism)
Secretes mucus to help with movement of food
Stores unused solid material till brain tells it to be voided
32 hours for food to pass!

13. Rectum Final straight portion of the large intestine
Stores solid waste and controls its release