Digestive System
•	Anatomy and Function
•	Functions
•	Convert food into smaller molecules that can be absorbed by cells
•	Remove solid waste
B. 2 Major components
	1. The Alimentary Canal (your food tube)
	2. Digestive glands
•	How does digestion relate to cellular respiration?
Digestive System
II. The Alimentary Canal
•	Mouth – Two types of digestion 
•	Mechanical digestion – Tear & crush food (chewing)
•	Chemical digestion
•	Saliva – produced by salivary glands, moisten food making it easier to chew
•	Contains amylase (breaks down carbs) and lysozyme (kills bacteria)
Digestive System
•	Pharynx (throat)
•	Connects mouth to esophagus
•	Swallow chewed up food ball called a bolus
•	Epiglottis covers the trachea – Why?
Digestive System
•	Esophagus
•	Moves food to the stomach by peristalsis (Fig. 38-11)
Digestive System
•	Stomach
•	Food mixes with hydrochloric acid (HCl) and pepsin to form chyme.
Digestive System
•	HCl activates pepsin
•	Pepsin breaks down large protein molecules into small chains of ????
Digestive System
•	After 1-2 hours, pyloric valve opens and chyme flows into the small intestine. 
Digestive System
F. Small Intestine
•	This is where most of your food is digested and absorbed
	3 Sections:
•	Duodenum (~ 1 foot long)
•	Digestive enzymes from the pancreas and the liver are added to the food.
•	The gall bladder adds bile
•	The pancreas adds sodium bicarbonate is also added…WHY?

Digestive System		
•	Jejunum (~ 3 feet) and Ileum (~ 6 feet)
•	The inside of the intestine is not smooth but has many small folds called villi and the villi have many microscopic folds called microvilli.
•	Why all of the folds?
•	Once absorbed, how do nutrients get to cells?
Where is your appendix?
Digestive System
•	Large Intestine (Colon)
•	Reabsorbs water from undigested material
What happens when too much water is absorbed? Too little? 
•	Bacteria in colon produce Vitamin K and live off undigested organic material (e.g. E. coli)
•	Bacteria generate gases (methane and hydrogen sulfide) as a by-product of their metabolism 
Large Intestine (Colon)
Alimentary Canal 
(Gastrointestinal “GI” Tract)
Accessory Organs
III. Digestive Glands
•	Liver
•	Detoxifies the blood
•	Stores vitamins and minerals
•	Converts foodstuffs from one form to another
•	Produces bile
III. Digestive Glands (cont)
•	Gall Bladder
1. Stores and releases bile
2. Bile emulsifies fats
•	Pancreas
•	Produces ???? And ????

Digestion Recap…