Human tongue neuroanatomy: Nerve supply and motor endplates.
ABSTRACT The human tongue has a critical role in speech, swallowing, and respiration, however, its motor control is poorly understood. Fundamental gaps include detailed information on the course of the hypoglossal (XII) nerve within the tongue, the branches of the XII nerve within each tongue muscle, and the type and arrangement of motor endplates (MEP) within each muscle. In this study, five adult human tongues were processed with Sihler's stain, a whole-mount nerve staining technique, to map out the entire intra-lingual course of the XII nerve and its branches. An additional five specimens were microdissected into individual muscles and stained with acetylcholinesterase and silver staining to study their MEP morphology and banding patterns. Using these techniques the course of the entire XII nerve was mapped from the main nerve to the smallest intramuscular branches. It was found that the human tongue innervation is extremely dense and complex. Although the basic mammalian pattern of XII is conserved in humans, there are notable differences. In addition, many muscle fibers contained multiple en grappe MEP, suggesting that they are some variant of the highly specialized slow tonic muscle fiber type. The transverse muscle group that comprises the core of the tongue appears to have the most complex innervation and has the highest percentage of en grappe MEP. In summary, the innervation of the human tongue has specializations not reported in other mammalian tongues, including nonhuman primates. These specializations appear to allow for fine motor control of tongue shape. Clin. Anat., 2010. (c) 2010 Wiley-Liss, Inc.
The Anatomical Record 07/1964; 149:279-97.
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Article: Organization of the hypoglossal motoneurons that innervate the horizontal and oblique components of the genioglossus muscle in the rat.[show abstract] [hide abstract]
ABSTRACT: Anatomical studies have shown the genioglossus muscle of the tongue of mammals to have at least two subdivisions. One is horizontal and the other fans out obliquely. In the dog, the hypoglossal nerve appears to have separate branches for each muscle subdivision. In the rat, genioglossus muscle motoneurons have been reported in the lateral and centrolateral subnuclei of the ventral hypoglossal nucleus. Here, retrograde labeling documented that these two hypoglossal sub-nuclei separately supply the two components of the genioglossus muscle. In so doing we add new data concerning the myotopic organization of the hypoglossal nucleus and further clarify the functional organization of the hypoglossal-tongue complex into protrusor and retrusor subdivisions.Brain Research 10/2002; 950(1-2):321-4. · 2.73 Impact Factor