1. The Digestive System
9th BIOLOGY

2. The Digestive System Ingests food
Breaks food into smaller pieces for absorption and use by the body.
Protein amino acids (building of body tissue)
Carbohydrates monosaccharides (glucose for synthesis of ATP, short term energy production)
Lipids fatty acids (long term energy storage)
Assimilation: using biomolecules to make new cellular tissue ( you are what you eat )

3. Types of Digestion: Mechanical digestion- Chemical digestion-
Chewing, churning of stomach (stomach is lined with smooth muscle)
Chemical digestion-
Breakdown of large molecules small using enzymes
Ex. Amylase in saliva

5. Organs of the Digestive System
Esophagus- muscular “food tube” from mouth to stomach
Moves food along via peristalsis- rhythmic contractions of involuntary smooth muscle
Epiglottis- small plate of cartilage that covers trachea when you swallow

6. Talk to a partner
Does any type of digestion occur in the esophagus? Which type?
What happens if food goes into your trachea?

7. Organs, cont. Stomach- “holding tank” for food
Gastric glands secrete hydrochloric acid (HCl) for pH of 2
Lined with mucus producing cells to protect stomach lining from acidic conditions
Pepsin released to digest proteins
Alcohol and aspirin are absorbed into bloodstream from stomach
Empty stomach- volume of 50ml, can expand to 2-4L when full

8. Stomach

9. Organs, cont.
Small intestine- 7 m long, 2.5cm diameter, pH in small intestine is 7
Intestinal walls continue peristalsis
Chemical digestion done with help from pancreas, liver, gallbladder
Pancreas- produces enzymes to digest food, also produces insulin, hormone that helps with glucose metabolism
Liver-produces bile to break down fats, 1L produced daily
Gallbladder- stores bile

10. Small Intestinal Villi: Structural folding increases absorptive surface area

11. Organs, cont. Large intestine-1.5 M long, 6.5cm diameter
Includes colon, rectum, appendix
Contains beneficial bacteria that produce vitamin K and some B vitamins
Primary function to absorb water
Indigestible material- feces
Contains intestinal cells, bacteria, cellulose, bile pigment
Expelled from body through rectum and anus

12. Large Intestine (Colon)

13. Talk to a partner
How do the large intestine and small intestine compare to each other?

14. Digestive Enzymes:
Bile and Lipase- (emulsifies fats)- breaks down lipids fatty acids
Pepsin- breaks down proteins amino acids
Amylase-breaks down carbohydratesmonosac charides (glucose)

15. Digestive Hormones:
Insulin- released by pancreas to allow glucose to enter cells for cellular respiration
No insulin produced?
Type I Diabetes, insulin injections necessary
Insulin resistant cells?
Type II diabetes, cells no longer respond to insulin, do not allow entry of glucose
Dietary changes, medications necessary

16. Digestive Hormones:
Glucagon: released by pancreas to induce the liver to release storage of glucose for use in cellular respiration.

17. Think-pair-share
What other body systems interact closely with the digestive system based on the information you learned today?