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Vertebrate teeth
Unique among vertebrates, usually capped with enamel
Lacking teeth: turtle and birds
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General characteristics of teeth in lower vertebrates
Homodont: teeth similar in appearance throughout mouth
Polyphyodont dentition: teeth are continuously replaced; ensures rejuvenation of teeth if worn/ broken
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General Characteristics of tetrapods
Heterodont- teeth differ in appearance throughout mouth
Polyphyodont- repitles
- diphyodont: two sets of teeth (mammalian)
- --> 1st set: deciduous dentition- milk/early teeth
- --> 2nd set= permanent dentition- adult/ mature teeth (includes molars)
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Vertebrate teeth attachment
- acrodont
- pleurodont
- thecodont
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acrodont
teeth attached in shallow sockets within the top surface of the jaw bone (weakest)
--> not very strong
--> allows for rapid replacement
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Pleurodont
teeth attached on the inner side and upper side of the jawbone that increases jawbone attachment area
- --> still conducive to polyphodont, but not as much
- --> stronger than acrodont, supports rapid replacement
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Thecodont
- Teeth attached by roots that are firmly fixed into sockets within the jawbone
- - strongest vertebrate tooth attachment
- - Largest surface area of tooth to jawbone
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Specialized teeth of lower vertebrates: teleost fish
most teleost fish--> teeth form abrasive surfaces used to scrape algae from rocks
--> acrodont tooth attachment
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Specialized teeth of lower vertebrates: sharks
teeth have sharp, knifelike edges along sides to pierce the skin; acrodont tooth attachment
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Specialized teeth of lower vertebrates: salamanders
- Differences between larval and metamorphosed adults
- - larval: pointed cone-shaped
- - adults: specialized teeth are bicuspid (having 2 cusps) and crown sits upon a basal pedicel, attached by collagenous fibers
--> when tooth replaced, crown is lost and pedicel quickly resorbed for rapid tooth replacement (acrodont tooth attachment)
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Reptilian teeth
display acrodont (snakes), thecodont (alligators), and pleurodont (lizards) tooth attachment
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Carnivorous reptiles
- teeth have sharply pointed cusps that penetrate skin and provide a firm hold on prey
- --> reverse curved teeth in front of mouth
- --> tip of tooth inclined forward from the rest of the tooth: better for grasping prey/ preventing escape- maxillary teeth
- --> open groves down which oral secretions flow during feeding
- --> venomous snakes: fangs- ends fuse to form a channel for venom from venom duct
- --> polyphyodont (regular replacement)
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Mammalian teeth- attachment
thecodont
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Mammalian teeth- types of teeth
four- incisors, canines, premolars, molars
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Mammalian teeth- Crown variations
brachydont-low crowns (humans, pigs)
hypsodont- high crowns (horses)
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Mammalian teeth- Cusp variations
- -rounded peaks [omnivores])
- -lophodont (cusps drawn out into predominately straight edges [horses, rhinos])
- - selenodont (crescent-shaped cusps (camels, deer))
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Specialized mammalian teeth
sectorial teeth
carnassials
tusks
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sectorial teeth
modified teeth with ridges on opposing teeth that slice by one another to cut tissue
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carnassials
used to cut sinew and muscle
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Tusks
- modified, elongated teeth
- --> elephants (incisors), Narqhals (spiraled upper left incisor), walrus (downward upper canines)
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Oral glands
groupings of epithelial cells that line the buccal cavity and secrete mucous and serous fluids
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Oral glands- fish
fish- rarely present due to moistening from watery medium
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Oral glands- tetrapods
prevalent
- -lack watery medium to moisten food
- --> salivary glands- most common, form and secrete saliva
- --> saliva: contains mucous, salts, proteins, and enzymes such as amylase (starch digestion)
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Oral glands- amphibians
Amphibians: mucous glands on tonge and a large intermaxillary gland located within the palate
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Oral glands- birds
- birds: most birds, especially water feeding birds, lack oral glands
- --> some passerine birds (perching birds with 3 toes and 1 toe back) use mucous oral secretions to aid in nest building
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Oral glands- reptiles
strips of glandular tissue (supralabial and infralabial glands) along upper and lower lips
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Types of oral glands in reptiles
- - lingual and sublingual glands (tongue)
- - premaxillary and nasal glands (snout)
- - palatine glands (roof of mouth)
- - Lacrimal and Hardesian glands
- - Duvernoy's gland (non-venomous snakes):
- - Venom gland (Duvernoy's homolog in venomous snakes)
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lingual and sublingual, premaxillary and nasal, palatine
release mucous to lubricate prey during swallowing
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Lacrimal and Hardesian glands
secretions bathe the eye and vomeronasal organ
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Duvernoy's gland
Found along posterior upper lip and releases a serous secretion that may help in digestion
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Venom gland
secretes toxic and digestive chemicals
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Oral glands- mammals
most common oral gland= salivary glands to produce saliva for lubrication and digestion
Found in three major pairs: mandibular, sublingual, parotid
Zygomatic gland can be found below zygomatic arch in dogs, cats, and other carnivores
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Mandibular
release secretions into floor of buccal cavity
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Sublingual
release secretions into floor of buccal cavity
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parotid
release secretions into floor of buccal cavity
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Liver
All vertebrates possess a liver that has the same basic microscopic structure
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What is the structure of the liver?
composed of sheets of hepatocytes separated by blood sinuses where courses of venous blood returning from intestines and arterial blood from the hepatic artery are filtered through
Liver is composed of multiple lobes
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Liver- snakes
Snakes- elongated and narrow within the tubular body cavity
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Liver: Protochordates/ Amphioxus
cecum from gut found near embryonic liver in vertebrate embryos, sometimes called the hepatic cecum
function: site of enzyme production and food absorption
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Gallbladder
function: bile storage and release during digestion
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Gall bladder presence or absence
Absent in jawless fish, most birds, few mammals
Present in cartilaginous and bony fish, amphibians, reptiles, few birds, most mammals
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Pancreas
present throughout vertebrates as an exocrine (pancreatic cells-digestive enzymes) and endocrine (pancreatic islets- blood glucose regulation) gland, although distinction may not always be discrete
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pancreas- jawless fish
Jawless fish: exocrine pancreas dispersed throughout submucosa and on the liver; Endocrine pancreas distinct, near bile duct; has a diffuse pancreas
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pancreas- sharks
Sharks: forms discrete gland with associated exocrine and endocrine components
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Pancreas- sharks
have a dorsal and ventral pancreas with two distinct structures
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Pancreas: bony fish
distinct exocrine and endocrine pancreas with clearly delineated pancreatic islets
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Pancreas- tetrapods
exocrine and endocrine pancreas always present as discrete organs near the duodenum
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