1. The Digestive System

2. Function~ Mechanical and chemical breakdown of food
Absorption of nutrients
Consists of alimentary canal and accessory organs

3. Characteristics of the Canal
Mucosa-protects tissues and carries absorption
Submucosa-glands, blood vessels, nerves
Muscular Layer-smooth muscle tissue, circular and longitudinal fibers, pushes food (PERISTALSIS)
Serosa-(serous layer) visceral perioneum, lubricates surfaces (serous fluid)

4. Digestion~ Contractions mix food with digestive juices.
Peristalsis – pushes food down the tube.

5. Ingestion~ Mouth mechanical digestion chemical digestion teeth saliva
breaking up food
chemical digestion
saliva
amylase
enzyme digests starch
mucin
slippery protein (mucus)
protects soft lining of digestive system
lubricates food for easier swallowing
buffers
neutralizes acid to prevent tooth decay
anti-bacterial chemicals
kill bacteria that enter mouth with food

6. Pharynx and Esophagus~
Pharynx – nasal and oral cavities: nasopharynx, oropharynx, and laryngopharynx
Esophagus – moves to the stomach
Cardiac sphincter – prevents food and chemicals from moving up out of stomach

7. mouth
break up food
moisten food
digest starch
kill germs

8. Stomach~ food storage disinfect food chemical digestion Functions
can stretch to fit ~2L food
disinfect food
HCl = pH 2
kills bacteria
breaks apart cells
chemical digestion
pepsin
enzyme breaks down proteins

9. mouth
break up food
moisten food
digest starch
kill germs
stomach
kills germs
store food
break up food
digest proteins
cardiac sphincter
pyloric sphincter

10. Small Intestine~ Function Structure
major organ of digestion & absorption
chemical digestion
digestive enzymes
absorption through lining
over 6 meters!
small intestine has huge surface area
Structure
3 sections
duodenum = most digestion
jejunum = absorption of nutrients & water
ileum = absorption of nutrients & water

11. Duodenum~ pancreas liver gall bladder 1st section of small intestines
acid food from stomach mixes with digestive juices from accessory glands:
pancreas
liver
gall bladder

12. Pancreas~ Digestive enzymes Buffers peptidases pancreatic amylase
reduces acidity
buffers acidity of material from stomach

13. mouth
break up food
moisten food
digest starch
kill germs
stomach
kills germs
break up food
digest proteins
store food
pancreas
produces enzymes to
digest proteins & starch

14. Liver~ Digestive System Functions Secretes bile
stored in gallbladder until needed
breaks up fats
maintains blood glucose
stores iron and vitamins
destroys damaged RBCs
removes toxic substances

15. mouth
break up food
moisten food
digest starch
kill germs
stomach
kills germs
break up food
digest proteins
store food
liver
produces bile
- stored in gall bladder
break up fats
pancreas
produces enzymes to
digest proteins & starch

16. Large Intestine~ Function not enough water absorbed back to body
re-absorb water
use ~9 liters of water every day in digestive juices
> 90% of water reabsorbed
not enough water absorbed back to body
diarrhea
too much water absorbed back to body
constipation

17. Rectum~ salts masses of bacteria undigested materials
Last section of colon (large intestines)
eliminate feces
undigested materials
extracellular waste
mainly cellulose from plants
roughage or fiber
salts
masses of bacteria

18. mouth
break up food
moisten food
digest starch
kill germs
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

19. Ulcers~ Used to think ulcers were caused by stress
Coevolution of parasite & host
Free of H. pylori
Colonized by H. pylori
Used to think ulcers were caused by stress
tried to control with antacids
Now know ulcers caused by bacterial infection of stomach
Helicobacter pylori
now cure with antibiotics
inflammation of stomach
inflammation of esophagus
H. pylori
cell damaging proteins
(VacA)
inflammatory proteins
(CagA)
cytokines
helper T cells
neutrophil cells
white blood cells