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27 Cards in this Set
- Front
- Back
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The human TMJ and masticatory muscles are adapted for what kind of diet?
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That of carnivores and herbavores
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5 characteristics of carnivore occlusion?
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1. teeth with high cusps
2. TMJ restricted mobility 3. TMJ at level of tooth row 4. Emphasis on temporalis muscle 5. Zygotmatic arch narrow |
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What is the predominant masticating muscle in carnivores?
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Temporalis
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A TMJ with restricted mobility has what kind of advantage?
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more vertical force in mandible because of fewer degrees of freedom
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5 characteristics of herbavores?
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1. teeth flat, low cusps
2. TMJ highly mobile 3. TMJ elevated above tooth row 4. Emphasis on masseter/medial pterygoid. 5. Zygomatic arch wide |
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What is the significance of the TMJ elevated above tooth row in herbavores?
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It allows large volumes of food consumed at a given time
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When COULD a TMJ be loaded?
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When resultant is posterior to the bite point and the muscle force exceeds bite force
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What type of animal has an unloaded TMJ?
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Rat
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What does it mean to be an unloaded TMJ?
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the jaw closing muscles are positioned anteriorly and the resultant passes through the bite point
(The mandible does not function as a lever) |
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The load will generally be higher when the resultant is (closer/more distant) from the bite point
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more distant
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What are the 2 basic precepts of muscle design?
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1. The force generated by a muscle is directly proportional to the cross-sectional area of all of its fibers (large muscles generate more force)
2. Individual muscle fibers are capable of shortening approximately 1/2 of their length |
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What are strap muscles?
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Muscles organized to produce a large range of movement (fibers that run the entire length of the muscle belly)
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What is an example of a strap muscle?
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Sartorius muscle of the thigh
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What are pennate muscles?
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muscles that are involved in power generation to have many more fivers but do not extend the entire length of the muscle belly
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What is an example of a pennate muscle?
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Deltoid of the shoulder
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2 strap muscles of the head?
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Lat. pterygoid (superior and inferior head) and digastric (anterior and posterior belly)
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2 multipennate muscles of the head?
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Masseter and med. pterygoid
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name a bipennate muscle of the head
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Temporalis
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On the head, where is the fulcrum of a first class system?
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on the axis of cervical spine
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Why is the first class lever system most efficient in the jaw?
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It yields the most work for the least amount of force
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Example of a second class lever?
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Wheelbarrow, nutcracker, mastication
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What is the fulcrum in a second class system?
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the opposing TMJ
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What type of efficiency do second class systems have?
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Intermediate efficiency
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2 examples of a third class system?
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drawbridge, biting
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What is the fulcrum in a third class system?
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TMJ
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What types of movements does a third class system produce?
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rapid, low force jaw movements
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T/F Third class systems generate large forces
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F they are inefficient for generating large forces, but are involved in other functions such as speech
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