1. The Digestive System

2. The Digestive System (Do Not Copy)
a system of organs that:
- takes in and breaks down food
- absorbs nutrients
- removes solid waste from the body
There are more similarities than differences among animal digestive systems

3. The Human Digestive System
There are 4 stages of digestion in humans: 1) Ingestion: taking in food (eating) 2) Digestion: physical and chemical breakdown of food a) physical: chewing action of teeth and churning action of stomach

4. The Human Digestive System
2) Digestion (continued)
b) chemical: enzymes in saliva, stomach and small intestine chemically break down food into small molecules (nutrients)
 liver, gall bladder & pancreas release substances (including enzymes) into small intestine

5. The Human Digestive System
Absorption:
nutrients, water, vitamins and minerals from the small and large intestine are absorbed into the bloodstream
 then can travel to other cells in the body
4) Egestion:
removal of solid waste products through the colon, rectum and anus

6. The Human Digestive System

7. The Human Digestive System
esophagus
stomach
liver
gall bladder
pancreas
small
intestine
large intestine
appendix
rectum
anus 7

8. Cool Facts (Do Not Copy)
Small intestine is lined with millions of villi (folds of the membrane) to maximize surface area for absorption
If all villi were unfolded, they would take up the area of a tennis court
Large intestine is full of “good” bacteria that help produce vitamins from nutrients
Our salivary glands produce
2 litres of saliva/day

9. Bacteria in our digestive system

10. Digestive Systems in Other Animals
Herbivores have much longer digestive systems than carnivores of the same size.
Why?
 Plant products are more difficult to digest
 More time and
surface area needed

11. The Fish Digestive System
Most fish are carnivores
Use teeth to grasp and swallow prey
(no physical digestion)
Long straight stomach allows fish to swallow animals almost the same size

12. The Fish Digestive System
Pyloric caeca (where stomach and intestine meet) carries out most digestion and absorption
Remaining nutrients absorbed in intestine with egestion through anus

13. The Bird Digestive System
Birds collect food in beak, but little physical digestion occurs there
Crop: special storage pouch
Food travels into first stomach segment – digestive juices added
Then into the gizzard that contains small stones to grind food
Absorption in intestine and egestion through cloaca (all- purpose “hole”)

15. The Frog Digestive System
Mouth is adapted to capture prey
Long tongue is sticky and moves very quickly to catch prey
Two types of teeth in upper jaw to hold prey as it is swallowed (no physical digestion)
Food can be held in gullet (wide, elastic esophagus)
Rest is similar to human, but egestion occurs through cloaca

16. The Frog Digestive System

17. The Frog Digestive System
Esophagus
Liver
Lungs
Gall bladder
Pancreas
Stomach
Small Intestine
Spleen
Large Intestine
Cloacal vent
Cloaca

19. Homework
Digestive System Comparison Worksheet