Suspension feeders
-sift small food particles through water
Clams
oysters
baleen whales
Substrate-feeders
-live in or on their food
Caterpillars, worms
Fluid-feeders
may be parasites that live on the fluid of other organisms
-aphids (on phloem sap of plants)
-mosquitoes (on blood of mammals)
May not be parasites
-hummingbirds and insects on nectar
Bulk-feeders
-eat large quantity of food
-most animals
Digestion occurs in specialized compartments
The simplest is the
gastrovascular cavity
No anus
Wastes leave via the mouth
Crop
-moisten & store
Gizzard
-grind
Intestine/ceca
-absorb
Oral cavity
Bulk-feeders
-eat large quantity of food
-most animals
Human Digestive System
• True digestive structures vs. accessory
structures
• Mechanical digestion vs. chemical
digestion
Digestion begins in the oral cavity:
chewing (mechanical digestion) and addition of
saliva to food to form a bolus
Salivary amylase digests starch and glycogen (chemical digestion)
Antibacterial agents
pharynx
Involuntary
contractions of
smooth muscle
surrounding the
digestive tract
propels food
Occurs in esophagus
and the intestines
Stomach structure
secrete pepsinogen.
secrete HCl
HCl converts
pepsinogen into pepsin
An adaptation which
prevents stomach from
digesting itself
Mucus cells secrete mucus
-lubricates and protects
stomach
Helicobacter pylori
Bile  emulsifies fat
Physically breaks up fat globules
Made in Liver
Stored in gall bladder
Including bicarbonate
Pancreatic enzymes
(released into the duodenum via
a duct)
•
•
•
•
Trypsin (protein digestion)
Pancreatic amylase (glycogen/starch)
Lipase (fats)
Nucleases (nucleic acids)
Intestinal enzymes
(from wall of small intestine)
• Disaccharidases (maltase,
sucrase, lactase)
• Dipeptidases
Anatomy of the small intestine
Villi
Blood vessels
-absorbs amino acids
-absorbs monosaccharides
-takes nutrient rich blood to liver
LACTEAL
-part of lymphatic system
-contains fluid called lymph
-collects components of fat
digestion
-will eventually empty into blood
vessels
Hepatic Portal system
Large
intestine
(colon)
Small
intestine
End
of small
intestine
Rectum
Anus
Unabsorbed
food material
Cecum
Appendix
Cecum is blind pouch at the intersection of the small and large
intestines
In humans it is a vestigial organ called the ????
Fig. 21-13a
Stomach
Small intestine
Cecum
Colon
(large
intestine)
Carnivore
Herbivore