_T. p._, Tensor palati; _L. p._, levator palati, concealed part
indicated by dotted line; _Pt. p._, pterygo-pharyngeus; _P. p._,
palato-pharyngeus; _St. p._, stylo-pharyngeus; _C. a._,
crico-arytenoideus post.; _C. th._, crico-thyroideus; _Th. c._,
thyroid cartilage (wing); _Th. h._, thyro-hyoideus; _K. h._,
kerato-hyoideus; _Th. c._, thyroid cornu; _S. c._, small cornu; _L.
p._, lingual process; _F. p._, foliate papilla; _Fu. p._, fungiform
papillæ. Part of great cornu is removed and indicated by dotted
line.
]
2. =Hyo-glossus.=—This is a wide, flat muscle, somewhat thicker than the
preceding. It lies on the lateral part of the root and body of the
tongue, partly under cover of the preceding muscle. Its deep face is
related to the genio-glossus. It arises from the lateral aspect of the
hyoid bone, from the lingual process to the oral extremity of the great
cornu, and from the thyroid cornu. The fibers pass obliquely forward and
upward, and for the most part turn toward the median plane of the dorsum
of the tongue. Its action is to retract and depress the tongue.
(It is usually possible to recognize in this muscle three portions,
which would correspond to the baseo-, kerato-, and chondro-glossus of
human anatomy.)
3. =Genio-glossus.=—This is a fan-shaped muscle, which lies parallel to
the median plane of the tongue. It is separated from the muscle of the
opposite side by a quantity of fat and connective tissue. It arises from
the inner surface of the ramus of the mandible near the symphysis. From
the tendon the fibers pass in a radiating manner, some toward the tip,
others toward the dorsum, and others toward the root of the tongue; some
fibers pass from the posterior end of the tendon to the body and small
cornu of the hyoid bone. The muscle as a whole is a depressor of the
tongue, and especially of its middle portion; when both muscles act, a
median groove is formed on the dorsum. The posterior fibers protrude the
tongue, the middle fibers depress the tongue, and the anterior fibers
retract the tip of the tongue.
=Vessels and Nerves.=—The arteries of the tongue are the lingual and
sublingual branches of the external maxillary artery. The sensory nerves
are the lingual and glosso-pharyngeal, and the muscles are innervated by
the hypoglossal nerve.