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Lecture 19

Lecture 19 zoo.doc

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ZOO 2090
Fred Laberge

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November 21 2011 Circulation Adptations -Blood shunt in the skin to disapate or keep it in the body -heat conservation by counter-current exchange -recycled heat is maintained close to body core, minimizing losses to the environment -between the blood and the vessel there is no gas exchange because the walls are too thick but heat can go through -exchanged with the blood that goes through the body -temperature is much lower the blood that goes through the fin -gradient of exchange is minimized at the tip of the fin -heat exchange between the blood vessels -temperature of the arteriolar blood and -same principle can be used using a carotid rete and turbinate bones to cool the brain -cool air come into extensive contact with blood in the turbinate’s, warming air before it gets to the lungs but also cooling blood that runs through the nose -this cool venous blood from the nose enters the carotid rete, where vessels multiple and are organized in opposite direction to the incoming carotid artery supplying the brain  selective brain cooing -might be involved in brain protection from heat stress or conservation of body water during exertion -saving water Lecture 19. diversity in digestive, urinary and reproductive systems Teeth -derived from bony dermal armor -composed of dentin, surmounted by a crown of enamel -used to eat and/or for defense Tooth Attachment -Acrodont  teeth attached to the outer air of the jawbone (most fishes) -Pleurodont attached to inner side (anurans, salamanders, many lizards) -thecodont teeth roots held in jawbone sockets( some fishes, crocodilians, fossil birds, mammals) Tooth Variation -Homodont teeth all the same size and shape -Heterodont teeth vary morphologically Tooth Replacement -Polyphodont teeth replace continuously throughout life -Diphyodont- Mammalian Teeth -heterodont dentition with species-specific number of teeth  evolved along with ability to chew -from front to rear: • Incisors (holding, cropping, or gnawing) • Canines (piercing flesh) • Premolars and molars  cheek teeth (shearing and grinding) Human formula: 2/2, 1/1, 2/2, 3/3 or 2-1-2-3(upper jaw –same as lower) -teeth of carnivores and herbivores are morphologically very different. The jaw has a diastema if tooth types are missing -flesh eater: their molars are designed to cut (blade like that go against each other) -herbivores: designed to grind (flatter surface) Trends in Terrestrial Vertebrates (see online) Stomach -better differentiated in tetrapods compared to fishes 1. Esophageal region only secretes mucus 2. Cardiac region (mammals only) only secretes mucus 3. Fundus secretes digestive en
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