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Human Tongue Anatomy
By peace | June 30, 2006
In humans, tongue function is critical for normal speech, swallowing and respiration; and tongue dysfunction can result in aphasia, dysphagia, and obstructive sleep disorders, respectively. At present there is a large discrepancy between the obvious importance of the tongue and our meager understanding of its structure and function. A major reason for this gap is that all tongues fall into the category of muscular hydrostats (MH); muscular organs whose biomechanical properties are more akin to hydraulic devices then the more familiar mechanical levers that constitute the skeletal muscle system1. MH are composed of muscle groups oriented in different directions and this makes them particularly hard to study by gross dissection or routine histological methods.
Tongue anatomy
The base of the tongue is located in the throat just above the larynx (voice box) and extends to the hyoid bone. The tongue is wrapped in the lingual membrane, which is studded with tiny projections called papillae. These papillae are responsible for the tongue’s textured surface. At the back, sides and tip of the tongue are the taste buds. These help to distinguish basic food flavours including bitter, salty, sweet and sour. There are about 9,000 taste buds on the average adult tongue. Some taste buds are found in the throat and palate.
The receptive cells for the sensation of taste are arranged in the form of taste-buds which are found chiefly on the tongue, but occur also in the soft palate and neighbourhood. The taste-buds are distributed very irregularly over the tongue, but are most numerous on its upper surface.
They are specially well marked along a A-shaped line near the back of the tongue, where they are grouped on the sides of papillae; these papillae are designated circumvallate, from the fact that each is surrounded by a little trench and wall.
Taste-buds are small ovoid bodies consisting of hair cells and supporting cells. The hair cells form a group in the centre of each bud, the hairlets projecting towards the free surface through a small opening termed the gustatory pore; the supporting cells are arranged around them somewhat like the staves of a barrel.
The terminal filaments of the nerves Gustatory pore and of taste surround the deeper ends of the hair cells. In the anterior two-thirds of the tongue the nerves of taste are the dendrites of cells of the geniculate ganglion - a sensory ganglion on the seventh cerebral nerve. The axons of these ganglion cells run inwards to the medulla and form arborisations around cells of a nucleus at the anterior end of the glossopharyngeal nucleus.
The pathway is continued from this into the opposite nesial fillet and thence to the cerebral cortex. The nerves of taste for the posterior third of the tongue are dendrites of cells of a ganglion on the glosso-pharyngeal nerve. The axons terminate round the glosso-pharyngeal nucleus whence the pathway of the impulses is continued through the opposite mesial fillet to the cerebral cortex.
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