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Comparative Anatomy Digestive System

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Presentation on theme: "Comparative Anatomy Digestive System"— Presentation transcript:

1 Comparative Anatomy Digestive System
Note Set 11 Chapter 13

2 Digestive System Six major subdivisions Oral cavity Pharynx Esophagus
Stomach Small & large intestine Rectum

3 Digestive System Agnatha - straight digestive tube
Coiled tube evolved with lengthening of tract Figure 11.1: Simple to complex digestive systems.

4 Oral Cavity Begins at mouth, ends at pharynx Tongue in floor of cavity
Palate in roof of cavity Primary palate Secondary palate Teeth Figure 11.2: Human oral cavity.

5 Palates Primary palate in anamniotes- nasal passageways empty into oral cavity Ex: Salamander Secondary palate of amniotes- extends to pharyngeal cavity Internal nares Figure 11.3: Oral cavity of amphibian (a) and mammal (b).

6 Teeth On jaws normally Cheeks in mammals form pocket
Acrodont teeth- fish and snakes Bicuspid- amphibians Tricuspid- lizards Pleurodont teeth- snakes Thecodont teeth- crocodilians Figure Types of cusps. Figure Cross section of jaw.

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

8 Bird Teeth Egg caruncle- all egg layers Not actual tooth
Structure epidermal, horny, keratinized On tip of snout To penetrate egg shell Figure 11.6: Egg caruncle of 15 day old owlet.

9 Reptilian Teeth Egg tooth- lizards and snakes Actual tooth Upper jaw
To penetrate egg shell Figure 11.7: Monitor egg tooth..

10 Modifications of Snake Teeth
Aglyphous- no modifications for venom delivery Solenoglyphous- retractable teeth, fangs Proteroglyphous- fangs in front of mouth Opisthoglyphous- fangs in back of mouth Figure 11.8: Position, cross and longitudinal sections of aglyphous (1), opisthoglyphous (2), and solenoglyphous (3) fangs.

11 Mammalian Teeth Incisors Canines Premolars & Molars
For cutting Ex: elephant tusks Canines For piercing Ex: walrus tusks Premolars & Molars To matriculate food Diastema- space without teeth; e.g., no canines Figure 11.9: Mammalian teeth specializations.

12 Mammalian Teeth Heterodont dentition Other varieties
Homodont- all teeth the same Bunodont- all teeth on single plain Sectorial teeth – carnassials; e.g., upper premolar and lower molar in carnivores

13 Dental Formula Catarrhines and humans have
=16 x 2 = 32 total teeth Canines: and If 0 is present, diastema is present Figure 11.10: Dental formulae.

14 Tongue Immobile in jawed fish Fleshy in higher vertebrates
Frog- tongue shoots out and draws back Glandular field secretes sticky fluid Immobile tongue- turtles, crocs, and some birds Flexible tongue- nectar feeding bats and snakes Forked tongue of snake Figure 11.11: Jacobson’s organ (sensing apparatus) of snake and forked tongue.

15 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 11.12: Swift and nest.

16 Pharynx In embryo, exhibits series of lateral pharyngeal pouches
Gives rise to various glands Slits in pharyngeal region Figure 11.13: Embryonic pharyngeal arches and oral development. Figure 11.14: Adult regions of pharynx.

17 Pharynx Constant Features in Tetrapods
Glottis-slit to larynx Covered by epiglottis Eustachian tube- opening Esophagus- opening Pharynx further subdivided for food and air passage Foramen cecum- groove on back of tongue Vestigial structure the leads to embryonic thyroid gland

18 Pharynx Figure 11.15: (a) Upper respiratory tract of human showing pharynx regions and (b) hyoid and larynx.


20 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 11.16: Esophagus and crop of bird.

21 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 11.17: Stomach of mammals with esophageal-like epithelia in gray and glandular epithelia in red.

22 Stomach Structure Greater and lesser curvature Messentaries
Greater omentum – attaches along greater curvature Lesser omentum – attaches along lesser curvature Cecum- increases surface area 2 parts in bird and crocodile stomach Proventiculus-glandular Gizzard- grinding mill (gastroliths)

23 4-Chambered Stomachs Rumen- food enters Reticulum- forms a bolus
Bacterial action Reticulum- forms a bolus Omasum- reswallowed grass Salivary action Abomasum- food worked out by gastric glands Figure 11.18: Stomach of calf.

24 Small Intestine Duodenum- 1st segment Bile and pancreatic ducts
Jejunum and Ileum subdivisions Figure 11.19: Digestive tract showing regions of small intestine.

25 Small Intestine Brunner’s Glands- mucous glands in duodenum and jejunum Peyer’s Patches- lymphatic nodules in ileum Crypts of Lieberkühns- intestinal glands at base of villi Lacteals- within villi—interior lymphatic vessels Transport fat molecules to circulatory system Valve of Kirckring- increases surface area

26 Small Intestine Figure 11.20: Histology of alimentary canal of a mammal showing various glands of small intestine.

27 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 region at rectum Cecum- aids in absorption Terminates at vermiform appendix Cloaca- common chamber for digestive, urinary, and reproductive products to empty (includes monotremes) Figure 11.21: Large intestine of human.

28 Liver Liver is diverticulum of primitive gut Liver produces bile
Bile stored in gallbladder Common bile duct Ampulla of Vater- terminal portion Figure 11.22: Development of liver and pancreas.

29 Pancreas Pancreas – diverticulum of gut
Duct of Santorini- small, dorsal pancreas Duct of Wirsung- large, ventral pancreas Accessory duct- large duct after small, dorsal duct disappears Exocrine and endocrine glands Islets of Langerhans- endocrine glands

30 Rectal gland- diverticulum in sharks

31 Literature Cited Figure 11.1, 11.3, 11.4, 11.5, 11.10, 11.15, 11.16, 11.17, & Kent, George C. and Robert K. Carr. Comparative Anatomy of the Vertebrates. 9th ed. McGraw-Hill, 2001. Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. McGraw Hill, 2002. Figure

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