Document Detail

Developmental changes in the shape of the supralaryngeal vocal tract in chimpanzees.
MedLine Citation:
PMID:  15386289     Owner:  NLM     Status:  MEDLINE    
The hyoid bone and larynx in human neonates are positioned as high as in other mammals. However, during postnatal life, they descend relative to the hard palate more rapidly compared with the horizontal growth of the oral cavity. This process is completed through the descent of the laryngeal skeleton relative to the hyoid, and through the descent of the hyoid relative to the cranial base. Thus, the human supralaryngeal vocal tract (SVT) develops to form a two-tube configuration with equally long horizontal and vertical parts. Longitudinal studies on living chimpanzee infants show that the descent of the larynx is more rapid than the horizontal growth of the oral cavity. This is primarily attributed to the descent of their larynges relative to the hyoid bone, but this is not accompanied by the descent of the hyoid. The present study, using embalmed specimens of chimpanzees, also shows that the horizontal and vertical parts of the SVT grow in chimpanzees similarly to humans during infancy. However, in chimpanzees, the horizontal part of the SVT grows greatly, whereas the vertical part of the SVT grows only slightly during the juvenile period. As a result, the chimpanzee larynx does not descend rapidly relative to the oral elongation during that period. Such differences may be related to the structural and morphological development of the facial skeleton and mandible, which affects prognathism and hyoid descent. These results support the hypothesis that the descent of the larynx evolved in at least two steps during hominoid evolution.
Takeshi Nishimura
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  American journal of physical anthropology     Volume:  126     ISSN:  0002-9483     ISO Abbreviation:  Am. J. Phys. Anthropol.     Publication Date:  2005 Feb 
Date Detail:
Created Date:  2005-01-20     Completed Date:  2005-03-22     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0400654     Medline TA:  Am J Phys Anthropol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  193-204     Citation Subset:  IM    
Copyright Information:
2004 Wiley-Liss, Inc.
Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan.
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MeSH Terms
Maxillofacial Development
Pan troglodytes / anatomy & histology,  growth & development*,  physiology
Vocal Cords / anatomy & histology,  growth & development*,  physiology

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