Friday, May 13, 2011

Your thirst and hunger centers tell you that you are dehydrated and hungry. You decide cold water and chicken wings will satisfy such desires. Specify the movements, muscles, bones and joints involved in opening your mouth and chewing the wings. Explain any and all movements individually across each joint involved specifying the actions involved (i.e. flexion, extension, etc.), the muscles causing such actions, the bones being pulled on by said muscles, the types of joints involved.

Mechanical digestion in the mouth results from mastication. Food is manipulated by the tongue, ground by the teeth, and mixed with saliva. Mastication is accomplished by a coordinated activity of the tongue, mandible, muscles of the mandible, and temporomandibular joints. Innervated by the fifth cranial nerve, the trigeminal nerve, the muscles involved in mastication – masseter, temporalis and pterygoid open and close the mouth. The lateral pterygoid muscles depress the mandible, opening the mouth, while the medial pterygoid, temporalis, and masseter elevate the jaw, closing the mouth. The jawbone itself, controlled by the temporomandibular joint (TMJ) - one of the only synovial joints with an articular disc, makes a rotational movement of opening and closing of the mouth. During jaw movements, only the mandible moves in excursions. Other muscles helping in the process of mastication are the cheeks, lips and tongue. Both intrinsic and extrinsic muscles of the tongue participate in mastication. The tongue maneuvers and crushes some of the food by pressing it against the hard palate, and forming it into a bolus, forcing it back of the mouth for swallowing. The cheeks and lips keep the food between the upper and lower teeth. Teeth participate as follows: Incisors cut into food; cuspids tear and shred; premolars and molars crush and grind.

Coleman, D. (Director). (2005). Anatomy for beginners: Lesson 3, Digestion. (Reality TV Show). United Kingdom.
Tortora, G.J., Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc. 

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