Tongue
THE TONGUE and it’s MUSCLES
Adapted from: Advance for Speech-Language Pathologists & Audiologists
May 26, 2003
Adult Tongue
The adult human tongue is specialized for speech. Its ability to change shape allows for articulation of every vowel and consonant that is in the repertoire of any language. The way the tongue changes shape for the different speech sounds is very important. Every shape is directly related to an individual sound of speech. The human tongue movements during speech are very different from tongue movements of other mammals.
The tongue is a hydrostat, which means that when a portion of the tongue contracts to shorten, another part of the tongue becomes wider, and vice versa.
Basic Anatomy of the Tongue
1. Longitudinal muscle: contraction shortens and widens the tongue
2. Vertical muscle: narrows and lenghtens the tongue
3. Transverse muscle: narrows and lenthens the tongue
These muscle orientations allow the different areas of the tongue to work independently. This allows the tongue to acheive the different shapes for speech articulation.
Muscle Fibers
2 Types
1. Slow (type I): These are involved in activities requiring precise control
of low force movements
2. Fast (type II): These are active in movements requiring a great amount of
force.
Recent Study
This study found that 56 percent of the human tongue muscle fibers are slow
muscle fibers, which is significantly greater than that any other mammalian
tongue. This data indicated that the ability to control small amounts of force
is unique to the human tongue muscle. The study also found that babies are born
with significantly reduced amounts of slow muscle fibers when compared to the
normal adult tongue. Infant tongue muscle fibers are more like that of monkeys
and other apes.
Another interesting finding was that the tongue of an adult with Parkinson’s disease had lost much of the specialized features that make the adult tongue unique.