Digestive System

Origin• Stomodeum and Proctodeum

• Buccopharyngeal membrane and cloacal membrane

Major Components• Digestive Tract• Buccal Cavity• Pharynx• Alimentary Canal

• Accessory Glands

Components: Buccal Cavity• Teeth, tongue, palate• Functions: Mechanical and chemical breakdown

Components: Buccal Cavity - Palate• Roof of the mouth• Primary Palate: contains internal nares• Medial series: Vomer, Pterygoid, Parasphenoid• Lateral series: Palatine, Ectopterygoid

• Secondary Palate: some reptiles and mammals• Hard and soft palate

Components: Buccal Cavity - Teeth• Origin: ectodermal• Mechanical breakdown, holding, hunting

Components: Buccal Cavity - Tongue• Evolution: Hypobranchial muscles resting on Hyoid Apparatus• Sensory, feeding

Components: Buccal Cavity - Tongue• Ingestion• Intraoral transport• Deglutition - swallowing

Components: Buccal Cavity - Tongue• Lingual feeding

Components: Pharynx• Common passage for food and air• Derivatives: Pharyngeal pouches meeting with branchial grooves,

further developing into other organs

Components: Pharynx• Swallowing/Deglutition• Air vs food

Components: Alimentary Canal• Esophagus• Stomach• Small Intestine• Large Intestine

• Terminus: Cloaca or Anus

Alimentary Canal Design• Mucosa, submucosa, muscularis externa, adventitia

Alimentary Canal Origin• Endoderm – lining• Mesoderm – muscles, CT, BV

Alimentary Canal Components: Esophagus

• Distendible, secretes mucus• Modifications: for abrasion (histologic), for large amounts of food

(histologic and behavioural)

Alimentary Canal Components: Stomach

• Storage, absorption, digestion• Gastric juice – HCl, mucus, enzymes• Rugae• Sections:• Cardiac – mucus• Fundus – Parietal and Chief cells• Pylorus – Neutralize, mucus

Alimentary Canal Components: Small Intestine

• Villi, Microvilli (absorption)• Crypts of Lieberkuhn (enzymatic)• Intestinal juice• Duodenum, jejunum, ileum• Duodenum – pancreatic and hepatic

secretions, Brunner’s glands (neutralize)• Jejunum• Ileum – ileocolic valve

Alimentary Canal Components: Large Intestine

• Simple columnar, terminus: stratification• Internal and external anal spinchther

Accessory Glands• Oral Glands • Buccal cavity• Mucus and serous fluid• More common in tetrapods• Examples: Salivary glands, lacrimal glands, venom glands

Accessory Glands• Liver• Developmental: RBC production• Adults: RBC destruction, filtering of wastes, bile production (exocrine)• Origin: hepatic diverticulum

Accessory Glands• Pancreas• Origin: Dorsal and ventral pancreatic diverticulum• Ducts lead to duodenum, contains trypsin and chymotrypsin (exocrine)• Islets of Langerhans: insulin and glucagon (endocrine)

Adaptations and Specializations of the GI• Fish: • Ileal modification – spiral valve – primitive osteichthyans, elasmobranches• Rectal gland - sharks• Pyloric cecum/ceca (absorption) - osteichthyes

Adaptations and Specializations of the GI• Terrestrial Vertebrates

Adaptations and Specializations of the GI• Gizzards

Adaptations and Specializations of the GI• Extended ceca

Adaptations and Specializations of the GI• Coprophagia

Images• http://www.perinatology.com/images/primarypalate.jpg• http://www.walgreens.com/marketing/library/graphics/images/en/1121.jpg• http://1.bp.blogspot.com/_W19ZkFqGT-M/Sz2ri8ZKWiI/AAAAAAAADZI/MdwPyTQFogI/

s400/Cows%2Bteeth%2BFM%2Bgood.jpg• http://courses.washington.edu/vertebra/452/photos/amphib/giant_toothrow.jpg• http://3.bp.blogspot.com/-xv3NJkxbs68/UGs9bygAySI/AAAAAAAAB1Q/MTv8jiK0lb8/

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• http://www.peteducation.com/images/articles/ill_reptile_teeth.gif• http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pregastric/cheekteeth.jpg• http://www.patzner.sbg.ac.at/Gobiidae/Fotos/Gob_buc_6.jpg• http://sharkmans-world.eu/images/teeth.jpg• http://www.tigerhomes.org/animal/images/diamondback-teeth.jpg• http://lrrpublic.cli.det.nsw.edu.au/lrrSecure/Sites/Web/gondwana/

Animal_Fossils_of_Gondwana/lo/fossils_06/graphics/tooth1.jpg• http://www.neuro.fsu.edu/~mmered/vomer/images/Snake.gif• http://www.wild-facts.com/wp-content/uploads/2009/10/cheats-chameleon.jpg• http://kuwaitiful.com/wp-content/uploads/2011/04/cats-tongue-close-up-magnifiy.jpg• http://sepetjian.files.wordpress.com/2011/10/embryoes2116.jpg• http://blogs.bu.edu/bioaerial2012/files/2012/09/Pelican-Wins1.jpg• http://reptilis.net/index4/swallow2.jpg• http://www.anatomyatlases.org/MicroscopicAnatomy/Images/Plate192.jpg

• http://www.zoology.ubc.ca/~millen/oldvertebrate/spiral20valve.jpg• http://health.rush.edu/healthinformation/graphics/images/en/15873.jpg• http://2.bp.blogspot.com/_euq4iPQ9iQk/TKNkGaP5KPI/AAAAAAAACfQ/HKzE6_pek9c/

s400/Chicken%2BGizzards%2BScreen%2BSaver.jpg• http://bio1152.nicerweb.com/Locked/media/ch41/41_27GITractComparison_CL.jpg• http://naturallycuriouswithmaryholland.files.wordpress.com/2012/01/1-19-12-snowshoe-

hare-scat-img_7235.jpg• http://4.bp.blogspot.com/_

zHWK8oRfUrU/TS_4jcpKQfI/AAAAAAAABfg/yqO5lgn8nKY/s1600/DSC_0010.JPG• http://1.bp.blogspot.com/-XTvsIwo9ouk/ToUu3JKafPI/AAAAAAAAGCs/Ussb_Yxaq2U/

s1600/EBV%2BPythonBunny7.jpg• http://courses.washington.edu/chordate/453photos/gut_photos/fundus_esophagus.jpg• http://www.aps.uoguelph.ca/~swatland/s140.gif• http://1.bp.blogspot.com/-XTvsIwo9ouk/ToUu3JKafPI/AAAAAAAAGCs/Ussb_Yxaq2U/

s1600/EBV%2BPythonBunny7.jpg• http://courses.washington.edu/chordate/453photos/gut_photos/fundus_esophagus.jpg• http://www.aps.uoguelph.ca/~swatland/s140.gif• http://

rsbl.royalsocietypublishing.org/content/early/2011/05/23/rsbl.2011.0336/F2.large.jpg• http://methiscool.files.wordpress.com/2012/04/21_04bhumandigestivesys-l.jpg• http://us.123rf.com/400wm/400/400/CathyKeifer/CathyKeifer1101/

CathyKeifer110100004/8537840-a-bog-eyed-tree-frog-is-trying-to-catch-a-fly-with-his-tongue.jpg