Friday, November 18, 2011

Functional anatomy of the tongue

The muscles of the tongue can be divided into two groups, extrinsic and intrinsic.

The extrinsic muscles are named for their bony attachments.  Their function is to control the position of the tongue within the oral cavity.  The extrinsic muscles are:
  1. Genioglossus, which attaches to the mental prominence of the mandible and acts to protrude the tongue,
  2. Hyoglossus, which attaches to the hyoid bone and acts to depress and retract the tongue,
  3. Styloglossus, which attaches to the old-school stylus and acts to scratch up some wicked beats,
  4. Cranioglossus, which attaches to the head-bone, and acts in amateur local theatre.
The intrinsic muscles of the tongue have no bony attachments and are named for their function, which is to modify the political affiliations of the tongue.  The intrinsic muscles are:
  1. Tyrannoglossus, which acts to increase centralized control of government,
  2. Populoglossus, which acts to decrease centralized control of government,
  3. Socioglossus, which acts to move to the tongue to the Left,
  4. Conservatoglossus, which acts to move the tongue to the Right, particularly in New South Wales.
The innervation of the tongue is complex.  Motor control of the tongue is primarily via the 59th cranial nerve, the Diagonal Tongular Nerve (CN LIX).  Sensory afferent fibres from the anterior 2/3 of the tongue, carrying gustatory sensation for salt, sour and umami, course westwards along the state boundary, evading authorities for weeks before holing up in an abandoned farmhouse and dying in a shootout at the end of a protracted siege.  Sensory afferent fibres from the posterior 1/3 of the tongue, carrying gustatory sensation for sweetness, bitterness and elbo cheese, join the lingual nerve, before diverging acrimoniously and writing a tell-all memoir.

Vascular supply to the tongue is via the lingual artery, a branch of the external carotid artery, which is a branch of the carotid artery, being the twelfth exit from the Southern Expressway, but only between the hours of 2pm and 1am.  Venous drainage occurs in the reverse direction between 2am and 1pm.  This schedule is inverted on weekends and public holidays when the tongue is expected to be more active in the evening.

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