Digestive System Overall Function Ingestion Digestion (physical & chemical) Absorption Waste elimination

Development Coelom forms from splitting of lateral plate mesoderm (hypomere) This is the pleuroperitoneal cavity through reptiles Parietal peritoneum Visceral peritoneum Dorsal & Ventral mesentery are folds of peritoneum

Endoderm Foregut Midgut Hindgut

General Morphology Typical gut wall has MUCOSA, SUBMUCOSA, MUSCULARIS, SEROSA

Gut motility Peristalsis Segmentation

Oral cavity/Oropharyngeal cavity Tongue – can extend from mouth beginning with amphibians Anchored by hyoid Helps to capture food, chew, swallow, taste food

Glands Venom Saliva Including several enzymes Anticoagulant in lampreys Nutrients in catfish Mucus

Snake venoms Copy and paste URL to link to original images at BIODIDAC http://biodidac.bio.uottawa.ca/thumbnails/filedet.htm?File_name=Rept005b&File_type=GIF

Teeth Dermal armor, dermal plates Placoid scales Homology to teeth

Teeth Dentin forms the majority of tooth and is a bone-like material made by odontoblasts

Teeth Enamel is the hardest substance in the body due to mineral content and is made by ameloblasts

Teeth The pulp cavity of the tooth contains the blood vessels and nerves The cementum covers the root of tooth and is made of acellular bone

Tooth attachment Acrodont – peak of jaws, teleosts Pleurodont – inner surface of jaws, amphibians, lizards Thecodont – sockets, crocodiles, extinct birds and mammals

Sets of teeth Polyphydont – many sets, typical of most vertebrates Diphydont – two sets, most mammals Monophydont – one set, platypus

Feeding Teeth New teeth forming

Shape of teeth Homodont – fish, amphibians, most reptiles, some marine mammals

Shapes of teeth Heterodont – later reptiles, most mammals Incisors - cutting teeth, chisel shaped Canine teeth – pointed for piercing & tearing Premolars – grinding teeth with 1-2 roots Molars – grinding teeth with 3 roots

Dental formulas Human: 2-1-2-3/2-1-2-3 = 32 Cat: 3-1-3-1/3-1-2-1 = 30 Cow: 0-0-3-3/3-1-3-3 = 32

Key Points What do you find unusual about the cow’s dental formula? What does this tell you about their eating habits? Can you think of another animal that would have the same unusual feature?

Herbivore Copy and paste URL to link to original images at BIODIDAC http://biodidac.bio.uottawa.ca/thumbnails/filedet.htm?File_name=mamm003b&File_type=GIF

Pharynx Fish – respiratory (gill) in function Tetrapods – throat, swallowing, location of tonsils in mammals

Pharynx in Tetrapods Common opening to airways via glottis Opening to middle ear via auditory tubes Opening to esophagus

Esophagus Can close in fish so stomach doesn’t become filled with respiratory water Birds may have CROP – sometimes has digestive enzymes & allows hoarding of food Pigeon milk is an esophageal secretion in doves for nestlings

Stomach Gastr- Anatomy –one or more chambers Pylorus, pyloric sphincter Greater & Lesser curvature Greater omentum, mammals only

Stomach Proventriculus – Contains digestive enzymes in birds (& crocodiles) Gizzard –grinding mill in bird

Ruminant Stomachs Rumen – cellulase & mucus release Reticulum – bolus formation for regurgitation Omasum – holding tank Abomasum – glandular portion

Stomach Physiology Receives, stores, liquefies, mixes food Chyme Zymogenic cells make pesinogen which breaks down protein Parietal cells make HCl which breaks down protein, activates pepsinogen & is anti-microbial

Stomach Physiology Most gastric secretions come from the goblet cells which make mucus to protect the lining of the stomach from its contents

Intestine Fish Straight No small & large intestine Typhlosole = spiral valve Coils Cecum/cecal

Digestive system Stomach Spiral valve

Intestine in Tetrapods Small Intestine Duodenum –mammals Jejunum –mammals Ileum –mammals Villi to increase surface area Blood vessels & lacteals for absorption

Small Intestine Function Finish chemical digestion Most nutrient absorption occurs in small intestine

Key Points Name two anatomical features that supports the function of the small intestine

Large Intestine in Tetrapods Cecum/ceca may be present in amniotes Colon is the majority of large intestine Rectum is the terminal segment of large intestine Function is formation & storage of feces, some water reabsorption, fermentation in herbivores

Liver & Gall Bladder Embryology – formed from diverticula of foregut and midgut Lesser omentum supports ducts & vessels & travels from lesser curvature of stomach to liver Bile duct – Common Bile Duct is formed by hepatic and cystic ducts & goes to duodenum

Key Point What are diverticula? What does the root “cyst-” mean?

Liver & Gall bladder Falciform ligament – liver to ventral body wall Function includes glucose storage, bile secretion, amino acid deamination, clotting factors, blood formation in fish Gall bladder store bile

Key Points You are investigating why hundreds of birds in a certain location died. You primarily are interested in conducting tests on the liver. Why? What would this tell you?

Pancreas Exocrine portion makes digestive juices that travel through pancreatic duct Acinar cells are the exocrine cells Juice contains amylase, lipase, protease

Key Points What does the pancreas make besides the exocrine juices?

Cloaca Receives digestive, urinary and genital structures below placental mammals

Key Points Name the four stomachs of the ruminant.