1. Digestion System Ms. Day/ AP Biology

2. Nutrition There are two parts to Nutrition: Ingestion Digestion
process of taking food into the digestive system so that it may be broken down
Digestion
the breakdown of food (either chemically or mechanically) in order to use its nutrients

3. Types of Nutrients Micronutrients- vitamins, minerals, & water
Macronutrients- proteins, lipids, carbohydrates, etc…

4. Types of Nutrients (Macromolecules)
Carbohydrates
sugars for energy and carbon skeleton structure (carbon chains)
Fats
broken down into fatty acids and glycerol
phospholipids for cellular membrane
Proteins
amino acids for protein synthesis
Nucleic Acids
Nucleotides for RNA and DNA synthesis

5. Other Types of Nutrients
Vitamins
usually work with enzymes  water soluble (excess excreted) and fat soluble vitamins (excess stored)
Minerals
inorganic substance- ex: calcium
Water
helps regulate body temp
act as a solvent (hydrolysis)

6. Human digestive system
After chewing and swallowing, it takes 5 to 10 seconds for food to pass down the esophagus to the stomach, where it spends 2 to 6 hours being partially digested.
Final digestion and nutrient absorption occur in the small intestine over a period of 5 to 6 hours.
In 12 to 24 hours, any undigested material passes through the large intestine, and feces are expelled through the anus.

7. Introduction to Digestive System
Used for breaking down food into nutrients
Nutrients then pass into the circulatory system and are taken to where they are needed in the body

8. There are 4 stages to food processing:
Ingestion: taking in food
Digestion: breaking down food into nutrients
Absorption: taking in nutrients by cells
Excretion: removing any leftover wastes

9. Step #1: The Mouth Food enters mouth MAIN FUNCTION:
Food is physically broken down by the teeth
Mechanical digestion
Then food is chemically broken down by amylase
Amylase = enzyme (helper molecule) in saliva
breaks down carbohydrates (sugars)
A bolus (soft lump) is formed with saliva and the tongue

10. Step #2: Swallowing MAIN FUNCTION:
Bolus is passed to the pharynx (throat) and the epiglottis makes sure the bolus passes into the esophagus and not down the windpipe!

11. Step #2: Swallowing (& not choking)
Epiglottis
flap of cartilage
closes trachea (windpipe) when swallowing
food travels down esophagus

12. Step #3: Esophagus and Peristalsis
MAIN FUNCTION:
Esophagus pushes food down to stomach
Peristalsis =
series of involuntary wave-like (smooth) muscle contractions  moves food DOWN the digestive tract

13. Step #4: Stomach Muscular sac  temporarily stores food
Gastric juices are secreted
Pepsin (enzyme) breaks down proteins
Water
Hydrochloric Acid (HCl)
MAIN FUNCTION:
Mechanically and chemically breaks down bolus
Bolus  chyme (liquid food)

14. Step #5: Small Intestine
MAIN FUNCTION =
Most chemical digestion takes place here
Nutrients are absorbed into blood
More sugar and protein breakdown
Amylase
enzyme breaks sugars
Trypsin
enzyme breaks proteins
Fats and DNA/RNA are also broken down
Lipase
Enzyme breaks down small fats
Nuclease
break down DNA/RNA

16. Step #5: Accessory Organs
1. Pancreas
Makes pancreatic juice
Contains trypsin, lipase, amylase, and nucleases AND sodium bicarbonate  neutralizes stomach acid
Releases juice into small intestines

17. Step #5: Accessory Organs
2. Liver
Makes bile
What does bile do?
Breaks down BIG fats pieces (globules)
Emulsify fats

18. Step #5: Accessory Organs
3. Gallbladder
stores bile
Releases bile into small intestines

20. Absorption in Small Intestines
Uses villi & microvilli
finger-like projections
increase surface area for absorption

21. VILLI

22. Step #6: Large Intestine (aka- the colon)
MAIN FUNCTION=
Water is absorbed using villi
Feces (solid) is made
undigestible solids (fibers)
Rectum
Holds solid wastes
Releases feces from body through anus

23. Enzymes Involved in Digestion

24. Animation on Digestive System
Quizzes (online to practice)

25. Digestion and Homeostasis
The endocrine, nervous, digestive and circulatory systems all work together to control digestion
HOW DOES DIGESTIVE SYSTEM HELP MAINTAIN HOMESTASIS?
Absorbing chemicals into blood (ex: calcium, glucose and nutrients)

27. Animation of Blood Glucose Regulation

28. Disruption in Homeostasis (stomach)
ULCERS
erosion of the surface of the alimentary canal generally associated with some kind of irritant

29. Disruption in Homeostasis (water balance & large intestines)
CONSTIPATION
a condition in which the large intestine is emptied with difficulty.
Too much water is reabsorbed
the solid waste hardens

30. Disruption in Homeostasis (water balance & large intestines)
DIARRHEA
a gastrointestinal disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine
This results in increased, multiple, watery feces
This condition may result in severe dehydration, especially in infants

31. Disruption in Homeostasis (large intestines)
APPENDICITIS
an inflammation of the appendix due to infection
Common treatment is removal of the appendix via surgery

32. Disruption in Homeostasis (Gallbladder)
GALLSTONES
an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder
Can either be “passed” (OUCH!!) or surgically removed

33. Disruption in Homeostasis (stomach and esphogus)
HEART BURN
ACID from the stomach backs up into the esophagus