What is the purpose?
Carbohydrates
monosaccharides (simple sugars)
Mouth
Proteins
amino acids
[minor energy source, major building block]
- mechanical digestion begins here
[major energy source, major building block]
fatty acids and glycerol
Lipids
- ingested food is pushed from the mouth by the tongue into the esophagus
Also absorbed: various vitamins and minerals and water
Salivary Glands
- chemical digestion is started by amylase, the enzyme present in saliva
- it breaks carbohydrates into polysaccharides and disaccharides
Intracellular Digestion
- There is no digestive activity
- cells take in and break down their own food
Extracellular Digestion (with no true digestive system)
Esophagus
Extracellular Digestion (with a true digestive system)
- the straight tube connecting the pharynx to the stomach and is 25cm in length.
Extracellular Digestion (true digestive system)
- digestive cavity or tube (serves as mouth and anus)
- gastrovascular cavity with no specialization
- wave-like muscle contractions called peristalsis move food to the stomach
- produces pepsin, hydrochloric acid, and digestive enzymes
Complete Digestive System
- two openings (mouth and anus)
- mostly one way passage of food
- mixes with a churning action
- largest gland in the body
- digestive tract (alimentary canal) usually broken into specialized regions
- produces bile, which is stored in the gall bladder
- Ex. earthworms, vertebrates
- bile breaks down fat into droplets
- produces an alkaline solution that neutralizes the acid in the stomach
- inner wall lined with villi
- Reabsorbs water and minerals into the blood
- transmits waste products to accumulate as feces in the rectum, which are then expelled from the body through the anus
- absorb nutrients through walls
- produces enzymes for digestion