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

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Presentation on theme: "Digestive System Overall Function Ingestion Digestion (physical & chemical) Absorption Waste elimination."— Presentation transcript:

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

2 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


4 Endoderm Foregut Midgut Hindgut


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


8 Gut motility Peristalsis Segmentation



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


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

14 Snake venoms


16 Teeth Dermal armor, dermal plates Placoid scales Homology to teeth


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


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


22 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


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


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


28 Feeding Teeth New teeth forming


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


32 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


34 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


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


38 HerbivoreHerbivore

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


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

42 Esophagus Can close in fish so stomach doesnt 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


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



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



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



53 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


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

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

57 Digestive system Stomach Spiral valve


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



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

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

64 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



67 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

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


70 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


72 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?

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


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

76 Cloaca Receives digestive, urinary and genital structures below placental mammals


78 Key Points Name the four stomachs of the ruminant.

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