Digestive Tract Anatomy

1. Digestive Tract Anatomy Digestive tract is interface between animal and environment All adaptations are compromises; a particular digestive tract anatomy enables an animal to do some things well and other things poorly

2. Avian Digestive Tract Beak Excellent example of adaptation to diet Galliform beaks undifferentiated Highly specialized beaks such as hummingbirds, crossbills, and snail kite Prepare food for swallowing Remove poorly digested portions (e.g. seed hulls, snail shells, bones)

3. Avian Digestive Tract Tongue � Has 3 primary roles Collecting food � sticky tongue of woodpeckers, long thin tongue hummingbirds Manipulating food in mouth Muscular tongue of finches and parrots for handling seeds Fish eating birds have stiff papilla Filter feeding birds have bristles that mesh with lamellae on bill to form sieve Swallowing � may have papilla to direct food items toward the back of the mouth

4. Avian Digestive Tract Figure 6-2B from King and McLelland

5. Avian Digestive Tract Taste buds � Birds have fewer than mammals, but they are functional Help bird assess the chemical content of food Example of grouse and acorns Salivary glands Lubricate food for swallowing Larger in birds that eat dry foods Amylase activity not significant Other functions:

6. Avian Saliva Gray jays use saliva to make balls of food to store in trees Sticky tongue of woodpeckers Swallow and swift nests Bird-nest soup

7. Esophagus Thin walled, highly folded tube, larger than in mammals Foods often in large pieces May serve as storage organ Crop Storage enables birds to consume a large amount of food and process later Food for young

8. Stomach � 2 parts Thin walled sacks in carnivores Proventriculus Glandular, produces acids and enzymes Ventriculus Muscular part of stomach (Gizzard) Grinds food into small particles (teeth) Large in herbivores

9. Small Intestine � Primary site digestion and absorption Pancreatic secretions Bicarbonate for buffering Proteases Amylase Lipase Liver secretions Bile salts

10. Ceca � blind pouches at junction of small and large intestine Contain microbes Fermentation Vitamins Nitrogen metabolism Water and electrolytes Large intestine Absorbs water and stores feces Cloaca

11. Herp GI-tract Larval form of amphibians often long undifferentiated tube Adult tract shorter Carnivorous reptiles have short tract Herbivorous species may have sites in large intestine for fermentation

12. Mammal Digestive Tract What advantage do most mammals have over most birds when it comes to digestion? Don�t have same weight restrictions Lips Assist in harvesting food and preparing for biting Tongue Many of the same functions as birds

14. Mammal Digestive Tract Teeth Incisors � Remove manageable sized bites Canines � Help carnivores capture and kill prey. Social function in many species. Molars and premolars � Reduce particle size and mix food with saliva Saliva Promotes taste by making chemicals soluble Enzymes break down starch Buffers acids in the rumen (bicarbonate) Proteins bind tannins

15. Mammal Digestive Tract Esophagus � tube from mouth to stomach Forestomach fermentation sites Ruminants most common, but also in camels, peccaries, hippos, kangaroos, leaf eating monkeys, hyraxes, and tree sloths Fermentation releases volatile fatty acids (fatty acids of 2, 3, or 4 carbons) which are energy source for animal Ruminants regurgitate food and chew it repeatedly.

16. Mammal Digestive Tract Rumen � Large sack with papillae. May have folds and sections Reticulum � Smaller sack with honey-comb appearance on inside. Is continuous with rumen Omasum � Chamber with folds like the pages of a book. Helps regulate which food particles are released from rumen Abomasum � Site of acid digestion

17. Ruminant Stomach

18. Mammal Digestive Tract Stomach of monogastic species is both a storage and digestive organ Carnivore stomach can hold large amounts of food Small intestine has same functions as we discussed in birds Ceca � Large blind pouch. Well developed in monogastric herbivores, esp. rodents, lagomorphs, horses

19. Mammal Digestive Tract Large intestine Site of fermentation in many herbivores Absorption of water and electrolytes from feces