1. The Digestive System
Chapter 22

3. Figure 41.6 Exploring: Four Main Feeding Mechanisms of Animals

4. Four stages of food processing

7. The Mouth Ingestion of food – Food ball = bolus Salivary glands
Mechanical digestion with teeth
Chemical digestion with saliva
Salivary glands
Secrete enzyme amylase
Starch breakdown starts here
Muscular tongue
Tasting
Helps with swallowing

8. The Pharynx Connects mouth to esophagus
Opens windpipe which leads to lungs
Epiglottis controls whether the pharynx is open to lungs or stomach

9. The Esophagus Muscular tube that connects pharynx to stomach
Moves food via peristalsis, waves of muscular contraction

10. The Stomach Large organ and functions as storage tank
Cells lining the stomach secrete gastric juice a fluid made up of
Hydrochloric acid
Digestive enzyme - pepsin for breaking down proteins into amino acids
Mucus – protects stomach
New product of stomach juices and food is now called chyme

11. Figure 41.11 The stomach and its secretions.

12. Stomach  Small Intestine Through the duodenum
First 10 inches of small intestine
Where most digestion occurs
Connected to
Liver
Gallbladder
Pancreas

13. Stomach  Small Intestine Pancreas
Pancreatic juices
Neutralize stomach acid
Contain enzymes that aid in digestion

14. Stomach  Small Intestine Liver and gall bladder
Gall bladder stores bile produced by liver
Bile has salts that
Break up fats
Contains dark pigments
Can crystallize into gall stones

15. Nutrient Absorption The Small Intestine
Without nutrient absorption we would eat and still starve.
The structure of the intestinal lining, or epithelium, is specialized for nutrient absorption
Lots of surface area!! (20 ft. long)
Villi
Microvilli

16. Figure 41.13 Nutrient absorption in the small intestine.

17. The Large Intestine
Twice as wide as small intestine – but shorter (5 ft. long)
At the junction of the small and large intestine is a small extension called the appendix.
The appendix contains white blood cells that make minor contributions to the immune system.
Appendicitis is a bacterial infection of the appendix

18. The Large Intestine – The colon
forms the main portion of the large intestine
absorbs water from the alimentary canal
produces feces, consisting of undigested material
About one-third of the dry weight of feces consists of bacteria from the colon

19. The Large Intestine – The rectum
The rectum, the last 15 cm (6 inches) of the large intestine, stores feces until they can be eliminated.
Two rectal sphincters regulate the opening of the anus
one voluntary
one involuntary
Relaxing the voluntary sphincter expels feces

20. Helpful review videos https://www.youtube.com/watch?v=s06XzaKqELk