Presentation on theme: "Comparative Anatomy Digestive System"— Presentation transcript:
1Comparative Anatomy Digestive System Note Set 11Chapter 13
2Digestive System Six major subdivisions Oral cavity Pharynx Esophagus StomachSmall & large intestineRectum
3Digestive System Agnatha - straight digestive tube Coiled tube evolved with lengthening of tractFigure 11.1: Simple to complex digestive systems.
4Oral Cavity Begins at mouth, ends at pharynx Tongue in floor of cavity Palate in roof of cavityPrimary palateSecondary palateTeethFigure 11.2: Human oral cavity.
5PalatesPrimary palate in anamniotes- nasal passageways empty into oral cavityEx: SalamanderSecondary palate of amniotes- extends to pharyngeal cavityInternal naresFigure 11.3: Oral cavity of amphibian (a) and mammal (b).
6Teeth On jaws normally Cheeks in mammals form pocket Acrodont teeth- fish and snakesBicuspid- amphibiansTricuspid- lizardsPleurodont teeth- snakesThecodont teeth-crocodiliansFigure Types of cusps.Figure Cross section of jaw.
7Jaw Teeth and Cheek Used for storage- rodents and squirrels Modified placoid scales- sharksPolyhyodont- permanent replacement of teethDiphyodont- two sets of teethMonophyodont- one set of teeth
8Bird Teeth Egg caruncle- all egg layers Not actual tooth Structure epidermal, horny, keratinizedOn tip of snoutTo penetrate egg shellFigure 11.6: Egg caruncle of 15 day old owlet.
9Reptilian Teeth Egg tooth- lizards and snakes Actual tooth Upper jaw To penetrate egg shellFigure 11.7: Monitor egg tooth..
10Modifications of Snake Teeth Aglyphous- no modifications for venom deliverySolenoglyphous- retractable teeth, fangsProteroglyphous- fangs in front of mouthOpisthoglyphous- fangs in back of mouthFigure 11.8: Position, cross and longitudinal sections of aglyphous (1), opisthoglyphous (2), and solenoglyphous (3) fangs.
11Mammalian Teeth Incisors Canines Premolars & Molars For cuttingEx: elephant tusksCaninesFor piercingEx: walrus tusksPremolars & MolarsTo matriculate foodDiastema- space without teeth; e.g., no caninesFigure 11.9: Mammalian teeth specializations.
12Mammalian Teeth Heterodont dentition Other varieties Homodont- all teeth the sameBunodont- all teeth on single plainSectorial teeth – carnassials; e.g., upper premolar and lower molar in carnivores
13Dental Formula Catarrhines and humans have =16 x 2 = 32 total teethCanines: andIf 0 is present, diastema is presentFigure 11.10: Dental formulae.
14Tongue Immobile in jawed fish Fleshy in higher vertebrates Frog- tongue shoots out and draws backGlandular field secretes sticky fluidImmobile tongue- turtles, crocs, and some birdsFlexible tongue- nectar feeding bats and snakesForked tongue of snakeFigure 11.11: Jacobson’s organ (sensing apparatus) of snake and forked tongue.
15Oral Glands Named based on location Birds have few oral glands Labial- near the lipsPalatal- near palateInternasalSublingual- releases venomParotid- salivary glandSubmaxillaryBirds have few oral glandsSwiftsFigure 11.12: Swift and nest.
16Pharynx In embryo, exhibits series of lateral pharyngeal pouches Gives rise to various glandsSlits in pharyngeal regionFigure 11.13: Embryonic pharyngeal arches and oral development.Figure 11.14: Adult regions of pharynx.
17Pharynx Constant Features in Tetrapods Glottis-slit to larynxCovered by epiglottisEustachian tube- openingEsophagus- openingPharynx further subdivided for food and air passageForamen cecum- groove on back of tongueVestigial structure the leads to embryonic thyroid gland
18PharynxFigure 11.15: (a) Upper respiratory tract of human showing pharynx regions and(b) hyoid and larynx.
20Esophagus Muscular tube connecting pharynx and stomach Can be short Crop- specialization in birdsOutpocketing of esophagusUsed to store foodPigeon’s milkFigure 11.16: Esophagus and crop of bird.
21Stomach Muscular chamber Secretes gastric juices Different lining of stomachsEsophageal-like epitheliaGlandular epitheliaRuminant stomach4 chambers: rumen, reticulum, omasum, abomasumHuman stomachCardiac sphincter- esophagusmeets stomachMostly lined with gastric epitheliumFigure 11.17: Stomach of mammals with esophageal-like epithelia in gray and glandular epithelia in red.
22Stomach Structure Greater and lesser curvature Messentaries Greater omentum – attaches along greater curvatureLesser omentum – attaches along lesser curvatureCecum- increases surface area2 parts in bird and crocodile stomachProventiculus-glandularGizzard- grinding mill (gastroliths)
234-Chambered Stomachs Rumen- food enters Reticulum- forms a bolus Bacterial actionReticulum- forms a bolusOmasum- reswallowed grassSalivary actionAbomasum- food worked out by gastric glandsFigure 11.18: Stomach of calf.
24Small Intestine Duodenum- 1st segment Bile and pancreatic ducts Jejunum and Ileum subdivisionsFigure 11.19: Digestive tract showing regions of small intestine.
25Small IntestineBrunner’s Glands- mucous glands in duodenum and jejunumPeyer’s Patches- lymphatic nodules in ileumCrypts of Lieberkühns- intestinal glands at base of villiLacteals- within villi—interior lymphatic vesselsTransport fat molecules to circulatory systemValve of Kirckring- increases surface area
26Small IntestineFigure 11.20: Histology of alimentary canal of a mammal showing various glands of small intestine.
27Large Intestine Fish and amphibians - straight and short Amniotes- divided into colon and rectumIleocecal valve- allows passage from small intestine into largeSigmoid flexure- S-shaped regionat rectumCecum- aids in absorptionTerminates at vermiform appendixCloaca- common chamber fordigestive, urinary, and reproductiveproducts to empty (includes monotremes)Figure 11.21: Large intestine of human.
28Liver Liver is diverticulum of primitive gut Liver produces bile Bile stored in gallbladderCommon bile ductAmpulla of Vater- terminal portionFigure 11.22: Development of liver and pancreas.
29Pancreas Pancreas – diverticulum of gut Duct of Santorini- small, dorsal pancreasDuct of Wirsung- large, ventral pancreasAccessory duct- large duct after small, dorsal duct disappearsExocrine and endocrine glandsIslets of Langerhans- endocrine glands
31Literature CitedFigure 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.FigureFigureFigureFigureFigureFigureFigureFigureFigureFigureFigure Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. McGraw Hill, 2002.Figure