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Comparative AnatomyDigestive System
Note Set 11
Chapter 13
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Digestive System
Six major subdivisions
Oral cavity
Pharynx Esophagus
Stomach
Small & large intestine Rectum
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Digestive System
Agnatha - straightdigestive tube
Coiled tube evolved withlengthening of tract
Figure 11.1: Simple to complex digestivesystems.
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Oral Cavity
Begins at mouth, ends atpharynx
Tongue in floor of cavity
Palate in roof of cavity
Primary palate
Secondary palate
Teeth
Figure 11.2: Human oral cavity.
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Palates
Primary palate inanamniotes- nasalpassageways empty into oral
cavity Ex: Salamander
Secondary palate of
amniotes- extends topharyngeal cavity
Internal naresFigure 11.3: Oral cavity of
amphibian (a) and mammal (b).
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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 11.4- Cross section of jaw.
Figure 11.5- Types of cusps.
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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 dayold owlet.
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Reptilian Teeth
Egg tooth- lizards and snakes
Actual tooth
Upper jaw
To penetrate egg shell
Figure 11.7: Monitor egg tooth..
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Aglyphous- no modificationsfor venom delivery
Solenoglyphous- retractable
teeth, fangs Proteroglyphous- fangs in front
of mouth
Opisthoglyphous- fangs in backof mouth
Modifications of Snake Teeth
Figure 11.8: Position, cross andlongitudinal sections of aglyphous (1),
opisthoglyphous (2), and solenoglyphous(3) fangs.
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Incisors For cutting
Ex: elephant tusks
Canines For piercing
Ex: walrus tusks
Premolars & Molars To matriculate food
Diastema- space withoutteeth; e.g., no canines
Figure 11.9: Mammalian teethspecializations.
Mammalian Teeth
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Mammalian Teeth
Heterodont dentition
Other varieties
Homodont- all teeth the same Bunodont- all teeth on single plain
Sectorial teethcarnassials; e.g., upper premolar andlower molar in carnivores
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Dental Formula
Figure 11.10: Dental formulae.
Catarrhines and humans have
2-1-2-3=16 x 2 = 32 total teeth
Canines: 3-1-4-2 and 3-1-4-3
If 0 is present, diastema is present
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Tongue
Immobile in jawed fish Fleshy in higher vertebrates
Frog- tongue shoots out and drawsback
Glandular field secretes sticky fluid
Immobile tongue- turtles, crocs,and some birds
Flexible tongue- nectar feedingbats and snakes
Forked tongue of snake
Figure 11.11: Jacobsons organ (sensing
apparatus) of snake and forked tongue.
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Oral Glands
Named based on location 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.
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Pharynx
In embryo, exhibits series of lateralpharyngeal 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.
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Pharynx
Figure 11.15: (a) Upper respiratory tract of human showing pharynx regions and(b) hyoid and larynx.
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Esophagus
Muscular tube connecting pharynxand stomach
Can be short
Crop- specialization in birds Outpocketing of esophagus
Used to store food
Pigeons milk
Figure 11.16: Esophagus and
crop of bird.
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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 withesophageal-like epithelia in gray and glandularepithelia in red.
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Stomach Structure
Greater and lesser curvature Messentaries
Greater omentumattaches along greater curvature
Lesser omentumattaches along lesser curvature
Cecum- increases surface area
2 parts in bird and crocodile stomach
Proventiculus-glandular
Gizzard- grinding mill (gastroliths)
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4-Chambered Stomachs
Figure 11.18: Stomach of calf.
Rumen- food enters Bacterial action
Reticulum- forms a bolus
Omasum- reswallowed grass Salivary action
Abomasum- food worked out
by gastric glands
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Small Intestine
Duodenum- 1stsegment
Bile and pancreatic ducts
Jejunum and Ileumsubdivisions
Figure 11.19: Digestive tract showing
regions of small intestine.
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Brunners Glands- mucous glands in duodenumand jejunum
Peyers Patches- lymphatic nodules in ileum
Crypts of Lieberkhns- intestinal glands at baseof villi
Lacteals- within villiinterior lymphatic vessels
Transport fat molecules to circulatory system
Valve of Kirckring- increases surface area
Small Intestine
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Small Intestine
Figure 11.20: Histology of alimentary canal of a mammalshowing various glands of small intestine.
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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.
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Figure 11.1, 11.3, 11.4, 11.5, 11.10, 11.15, 11.16, 11.17, 11.18 & 11.22- Kent, George C. and Robert K.Carr. Comparative Anatomy of the Vertebrates. 9th ed. McGraw-Hill, 2001.
Figure 11.2- http://www.mouth-cancer-symptoms.com/
Figure 11.6- http://gargravarr.cc.utexas.edu/owl/2002/
Figure 11.7- http://www.proexotics.com/collection_nonPE9.html
Figure 11.8- http://www.kingsnake.com/reptilia-italia/My_HomePage_file/snakesgeneral.htm
Figure 11.9- http://www.okc.cc.ok.us/biologylabs/Documents/zoology/22
Figure 11.11- http://www2.worldbook.com/features/reptiles/html/body_senorg.html
Figure 11.12- http://www.rspb.org.uk/birds/whatyoucando/attracthousemartins/index.aspFigure 11.13- http://people.eku.edu/ritchisong/342notes7.html
Figure 11.14- http://www.cortexity.com:8080/nicksblog/
Figure 11.19- http://www.yoursurgery.com/ProcedureDetails.cfm?BR=1&Proc=49
Figure 11.20- Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. McGraw Hill,2002.
Figure 11.21- http://www.becomehealthynow.com/popups/lrg_intest.htm
Literature Cited
Recommended