1. Digestive System
Midterm Content

2. 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.

3. Mouth Teeth - mechanical digestion Saliva - chemical digestion
break up food
Saliva - chemical digestion
amylase enzyme digests starch
All that in spit

4. Esophagus –Swallowing (& not choking)
Epiglottis
flap of cartilage
closes trachea (windpipe) when swallowing
food travels down esophagus
Peristalsis
involuntary muscle contractions to move food along
PHARYNX goes to the esophagous that carries food to stomach and also connects to TRACHEA that carries air to lungs

5. Small intestine Functions digestion absorption digest carbohydrates
amylase from pancreas
digest proteins
trypsin & chymotrypsin from pancreas
digest lipids (fats)
bile from liver & lipase from pancreas
absorption
nutrients move into body cells by:
diffusion
active transport
About every 20 seconds, the stomach contents are mixed by the churning action of smooth muscles.
As a result of mixing and enzyme action, what begins in the stomach as a recently swallowed meal becomes a nutrient-rich broth known as acid chyme.
At the opening from the stomach to the small intestine is the pyloric sphincter, which helps regulate the passage of chyme into the intestine.
A squirt at a time, it takes about 2 to 6 hours after a meal for the stomach to empty.

6. Absorption in Small Intestines
Nutrient absorption through villi
finger-like projections
increases surface area for absorption
SMALL INTESTINES 6 meters long, but can stretch to cover a tennis court

7. Liver & Gall Bladder Produces bile breaks up fats
gallbladder only stores bile
that’s why you can have your gall bladder removed
bile contains colors from old red blood cells collected in liver =
iron in RBC rusts & makes feces brown

8. Large intestines (colon)
Function
re-absorbs water
not enough water re-absorbed
Diarrhea
too much water re-absorbed
constipation

9. Rectum Last section of large intestines eliminate feces
what’s left over?
undigested materials
mainly cellulose from plants
called roughage or fiber
keeps everything moving & cleans out intestines
masses of bacteria

10. You’ve got company!
Living in the large intestine is a community of helpful bacteria
Escherichia coli: E. coli
Help digest cellulose
digests fruits & vegetables
produce vitamins
vitamin K & B vitamins
BUT generate gases
by-product of bacterial metabolism
methane, hydrogen sulfide
STINKY!

11. mouth
break up food
digest starch
kill germs
moisten food
stomach
kills germs
break up food
digest proteins
store food
liver
produces bile
- stored in gall bladder
break up fats
small intestines
breakdown food
- proteins
- starch
- fats
absorb nutrients
pancreas
produces enzymes to
digest proteins & carbs
large intestines
absorb water

12. Trivia 1 The function of the digestive system is to . . .
chemically break down food
absorb nutrient materials
mechanically break apart food
all of the above

13. Trivia 2
The villi of the small intestine allow for an increase in the rate of . . .
nutrient absorption
acid production
cellulose digestion
bile production
absorption

14. Enzymes in saliva begin the chemical digestion of . . . fat Protein
Trivia 3
Enzymes in saliva begin the chemical digestion of . . .
fat
Protein
carbohydrates
vitamins
carbohydrates

15. Where does protein digestion start in the human body?
Trivia 4
Where does protein digestion start in the human body?
the mouth
the stomach
the small intestine
large intestine
Stomach and then small intestine

16. The main function of the large intestine is to: store waste
Trivia 5
The main function of the large intestine is to:
store waste
absorb water from digested food
digest proteins
none of the above
Absorb water