1. Comparative Anatomy Digestive System
Kardong
Chapter 13
Part 11

2. Digestive System Agnatha - a straight digestive tube
Coiled tube evolved with lengthening of tract
Figure Simple to complex digestive systems—lower verts and birds (book figure 13.27).

3. Figure 11.2. Simple to complex digestive systems—m ammals (book figure 13.28).

4. Digestive System Six major subdivisions Buccal cavity Pharynx
Esophagus
Stomach
Small & large intestine
Rectum

5. Buccal Cavity Begins at mouth, ends at pharynx
Tongue in floor of cavity
Palate in roof of cavity
Primary palate
Secondary palate
Teeth
Figure Buccal cavity in
monkey and shark.

6. Palates
Primary palate in anamniotes- nasal passageways empty into buccal cavity
Ex: Salamander
Secondary palate of amniotes- extends to pharyngeal cavity
Internal nares
Figure Buccal cavity of amphibian (a) and mammal (b).

7. Teeth Figure 11.5. Types of cusps (book figure13.15).
On jaws normally
Cheeks in mammals form pocket
Acrodont teeth- fish
Bicuspid- amphibians
Tricuspid- lizards
Pleurodont teeth- snakes
Thecodont teeth-
crocodilians
Figure Types of cusps (book figure13.15).
Figure Cross section of jaw (book figure 13.10).

8. Cheek and Jaw Teeth Used for storage- rodents and squirrels
Modified placoid scales- sharks
Polyphyodont- permanent replacement of teeth
Diphyodont- two sets of teeth
Monophyodont- one set of teeth

9. Reptilian Egg Tooth Egg tooth - reptiles and snakes Actual tooth
Upper jaw
To penetrate eggshell
Figure Monitor egg tooth.

10. Bird Egg Tooth Egg caruncle- all egg layers Not actual tooth
Structure epidermal, horny, keratinized
On tip of snout
To penetrate eggshell
Figure Egg caruncle of 15 day old owlet.

11. Specialized Modifications of Snake Teeth
Aglyphous- no modifications for venom delivery
Solenoglyphous- retractable teeth, fangs
Proteroglyphous- fangs in front of mouth - cobras
Opisthoglyphous- fangs in back of mouth – rear-fanged
species (hognose snake)
Figure Position, cross and longitudinal sections of aglyphous (1), opisthoglyphous (2), and solenoglyphous (3) fangs.

12. Mammalian Teeth Incisors Canines Premolars & Molars
For cutting
Ex: elephant tusks
Canines
For piercing
Ex: walrus tusks
Premolars & Molars
To matriculate food
Diastema- have incisors but no canines
Figure Mammalian teeth specializations
(heterodont dentition).

13. Figure Deciduous and
permanent teeth (carnassials
shaded). (book figure 13.7)

14. Dental Formula Catarrhines, including humans, have
=16 x 2 = 32 total teeth
Canids: and
If 0 is present, diastema is present
Figure Dental formula
for mammals.

15. Tongue Immobile in jawed fish Fleshy in higher vertebrates
Frog- tongue shoots out and draws back
Glandular field secretes sticky fluid
Immobile tongue- turtles, corcs, and some birds
Flexible tongue- nectar-feeding bats and snakes
Forked tongue of snake
Figure Jacobson’s organ (sensing apparatus) of snake.

16. Oral Glands Named based on location Birds have few oral glands
Labial- near the lips
Palatal- near palate
Internasal
Sublingual- releases venom
Parotid- salivary gland
Submaxillary
Birds have few oral glands
Swifts
Figure Swift and nest.

17. Figure 11.15. Oral glands of reptiles

18. Pharynx In embryo, exhibits series of lateral pharyngeal pouches
Gives rise to various glands
Slits in pharyngeal region
Figure Embryonic pharyngeal arches and oral development.
Figure Adult regions of pharynx.

19. Pharynx Constant features in tetrapods
Glottis-slit to larynx
Covered by epiglottis
Eustachian tube- opening
Esohagus- opening
Pharynx further subdivided for food and air passage
Foramen cecum- groove on back of tongue
Vestigial structure that leads to thyroid gland

20. Pharynx
Figure (a) Upper respiratory tract of human showing phayrnx regions and
(b) hyoid and larynx.

21. Esophagus Muscular tube connecting pharynx and stomach Can be short
Crop - specialization in birds
Outpocketing of esophagus
Used to store food
Pigeon’s milk
Figure Esophagus, crop, and stomach of bird (see book figure 13.32).

22. Stomach Muscular chamber Secretes gastric juices
Different lining of stomachs
Esophageal-like epithelia
Glandular epithelia
Ruminant stomach
4 chambers: rumen, reticulum, omasum, abomasum
Human stomach
Cardiac sphincter- esophagus
meets stomach
Mostly lined with gastric epithelium
Figure Stomach of mammals with esophageal-like epithelia in gray and glandular epithelia in red.

23. Stomach Structure Greater and lesser curvature Messentaries
Greater omentum
Lesser omentum
Cecum - increases surface area
2 parts in bird and croc stomach
Proventiculus-granular
Gizzard- grinding mill (gastroliths)

24. Four-chambered Stomachs
Rumen - food enters
Bacterial action
Reticulum - forms a bolus
Omasum - reswallowed gras
Salivary action
Abomasum- food worked out by gastric glands
Figure Stomach of calf
(see book figure 13.43).

25. Small Intestine Duodenum - 1st portion Bile and pancreatic ducts
Jejunum and ileum subdivisions
Figure Digestive tract showing regions of small intestine in humans.

26. Small Intestine Brunner’s Glands- mucous glands in duodenum
Peyer’s patches- lymphatic nodules in ileum
Crypts of Lieberkühn - intestinal glands at base of villi
Lacteals- in villi within interior lymphatic vessels
Transport fat molecules to circulatory system
Valve of Kirckring- increases surface area

27. Small Intestine
Figure Histology of alimentary canal of a mammal showing various glands of small intestine.(book figure 13.26).

28. Large Intestine Fish and amphibians - straight and short
Amniotes - divided into colon and rectum
Ileocecal valve - allows passage from small intestine into large
Sigmoid flexure - S shaped at rectum
Cecum - aids in absorption
Terminates at vermiform appendix
Cloaca - common chamber for
digestive, urinary, and reproductive
products to empty
Figure Large intestine of human.

29. Liver Liver is endodermal diverticulum Liver produces bile
Bile stored in gallbladder
Common bile duct
Ampulla of Vater - terminal portion of common bile duct
Figure Development of liver and pancreas (book figure 13.38).

30. Pancreas Pancreas is a diverticulum
Most people have a single pancreatic duct
Duct of Santorini - small, dorsal (accessory)
Duct of Wirsung - large, ventral
- functional duct after small, dorsal accessory duct disappears
Exocrine and endocrine glands
Islets of Langerhans- endocrine glands

31. Rectal gland- diverticulum in sharks “A Notable Duct”
Duct of Cuvier or Common Cardinal
Cuvier was founder of Comparative Anatomy and Paleontology
2 ducts of Cuvier in most vertebrates – See Circulatory System