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A Three-Dimensional Atlas of Human
Tongue Muscles
IRA SANDERS
1
AND LIANCAI MU
2
*
1
Alice and David Jurist Institute for Biomedical Research, Hackensack University Medical
Center, Hackensack, New Jersey
2
Upper Airway Research Laboratory, Department of Research, Hackensack University
Medical Center, Hackensack, New Jersey
ABSTRACT
The human tongue is one of the most important yet least understood
structures of the body. One reason for the relative lack of research on the
humantongueisitscomplexanatomy.Thisisarealbarriertoinvestiga-
tors as there are few anatomical resources in the literature that show this
complex anatomy clearly. As a result, the diagnosis and treatment of
tongue disorders lags behind that for other structures of the head and
neck. This report intended to fill this gap by displaying the tongue’s anat-
omy in multiple ways. The primary material used in this study was serial
axial images of the male and female human tongue from the Visible
Human (VH) Project of the National Library of Medicine. In addition, thick
serial coronal sections of three human tongues were rendered translucent.
The VH axial images were computer reconstructed into serial coronal sec-
tions and each tongue muscle was outlined. These outlines were used to
construct a three-dimensional (3D) computer model of the tongue that
allows each muscle to be seen in its in vivo anatomical position. The thick
coronal sections supplement the 3D model by showing details of the com-
plex interweaving of tongue muscles throughout the tongue. The graphics
are perhaps the clearest guide to date to aid clinical or basic science inves-
tigators in identifying each tongue muscle in any part of the human
tongue. Anat Rec, 296:1102–1114, 2013. V
C2013 Wiley Periodicals, Inc.
Key words: tongue; intrinsic and extrinsic tongue muscles; neu-
romuscular compartments; tongue movement;
speech; swallowing; respiration; 3D reconstruction
In humans, tongue function is critical for normal
speech, swallowing, and respiration (Hiiemae and Palmer,
2003); and tongue dysfunction can result in aphasia, dys-
phagia, 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
in our knowledge is that all tongues fall into the category
of muscular hydrostats; muscular organs whose biome-
chanical properties are more akin to a hydraulic system
then the more familiar mechanical levers that constitute
the skeletal muscle system (Kier and Smith, 1985). Mus-
cular hydrostat (MH) is composed of muscle groups ori-
ented in different directions and this makes them
Grant sponsor: Shannon Award and NIH from National Insti-
tute on Deafness and Other Communication Disorders; Grant
number: R01 DC004684, R01 DC004728.
*Correspondence to: Liancai MU, M.D., Ph.D., Upper Airway
Research Laboratory, Department of Research, Hackensack
University Medical Center, Hackensack, New Jersey 07601.
E-mail: lmu@humed.com
Received 23 July 2012; Accepted 3 April 2013.
DOI 10.1002/ar.22711
Published online 6 May 2013 in Wiley Online Library
(wileyonlinelibrary.com).
THE ANATOMICAL RECORD 296:1102–1114 (2013)
V
V
C2013 WILEY PERIODICALS, INC.
particularly hard to study by gross dissection or routine
histological methods.
Although the tongues of some birds, amphibians, rep-
tiles, and mammals have been studied (Abd-El-Malek,
1938a; Lombard and Wake, 1976; Hellstrand, 1980,
1981; Gans and Gorniak, 1982; Bhattacharyya, 1985;
Delheusy et al., 1994; Herrel et al., 1998; Nishikawa
et al., 1999; Mu and Sanders, 1999, 2010), we are far
from understanding the relationship between muscle
structure and function within tongues. Gross tongue
motion caused by contraction of any individual muscle is
dependent on the activity of surrounding muscles.
Because of this complexity there are few studies that
demonstrate the activity of any intrinsic tongue muscle,
either by electromyographic recording during gross
tongue movement, or by electrical stimulation of a single
isolated muscle. Therefore, the actions of the individual
tongue muscles are largely assumptions based on their
anatomical arrangement and extrapolation from animal
experiments (Abd-El-Malek, 1938a; Hellstrand, 1981;
Gilliam and Goldberg, 1995). At present, gross tongue
movements are believed to result from a complex mix-
ture of individual tongue muscles acting as agonists,
antagonists, or stabilizers (Lowe, 1980). However, the
details of how any movement is accomplished are
unknown.
TONGUE BASE, BODY, AND BLADE
Anatomists and speech scientists use different termi-
nology to describe the parts of the tongue and this can
be a source of confusion. In this study, the tongue is di-
vided into three parts: the blade, body, and base. The
base, or root, is that part of the tongue posterior to the
sulcus terminalis, the line of circumvallate papillae taste
receptors. The body extends from the circumvallate pap-
illae to the frenulum, the anterior part of the genioglos-
sus (GG) muscle. The blade is the region of the tongue
anterior to the frenulum. The body is the largest seg-
ment and it convenient to arbitrarily separate the body
into an anterior and posterior part. The anterior body is
inferior to the hard palate; the posterior body lies infe-
rior to the soft palate.
Basic Tongue Muscular Anatomy
The tongue muscles of most mammals are divided into
two main groups: the extrinsic and the intrinsic (Sonn-
tag, 1925). The extrinsic muscles have one attachment
to a bone (mandible, hyoid bone, or styloid process) while
the other end inserts within the tongue. In contrast, the
intrinsic muscles originate and insert within the tongue
and have no bony attachments. Generally, the extrinsic
muscles tend to move the position of the whole tongue
while the intrinsic muscles change its shape.
Some authors describe a greater number of extrinsic
muscles than those in this study. We excluded the pala-
toglossus (PG), the muscle of the anterior tonsillar pillar;
the glossopharyngeus (GP), a slip from the superior pha-
ryngeal constrictor (SPC) that connects to the tongue;
and the chondroglossus (CG), a small muscle that is
sometimes considered to be part of the hyoglossus (HG)
muscle. These muscles are not thought to make large
contributions to tongue movements and were excluded
as they would make the three-dimensional (3D) model
needlessly complex.
In this article, the term tongue is used to refer to the
intrinsic tongue, that part of the tongue encapsulated by
connective tissue. The intrinsic tongue includes all of
the intrinsic muscles plus the internal parts of the ex-
trinsic muscles. The extrinsic tongue refers to those
parts of the extrinsic muscles outside the tongue. The
whole tongue refers to the intrinsic tongue plus the
external parts of the extrinsic muscles. The dorsum
refers to the superior surface of the tongue.
The main connective tissue structures in the tongue
include: the medium septum, a thick sheet of fascia in
the midline of the tongue that serves as origin for the
transverse muscle; the paramedian septum, fascia that
separate the GG muscle from the inferior longitudinal
(IL) muscle; the lateral septum, connective tissue that
envelopes the IL muscle.
BASIC CONCEPTS OF TONGUE
BIOMECHANICS; THE TONGUE IS A
MUSCULAR HYDROSTAT
The tongue, like the tentacles of an octopus or trunk
of an elephant, is a MH (Kier and Smith, 1985). MHs
are muscular structures without bones whose biome-
chanics are more like a hydraulic system than the me-
chanical lever arms used by most skeletal muscles. The
connective tissue keeps the volume of the organ constant
during muscle contractions. Therefore, if a muscle con-
tracts to shorten the MH, the MH becomes wider. Simi-
larly, contraction of muscles that are oriented in the
cross-sectional plane of the muscular hydrostat will nar-
row the MH and simultaneously lengthen it. In addition
to shortening and lengthening, MHs can twist in various
directions depending on muscle arrangement and selec-
tive activation.
The same principles are believed to apply to tongue
movement. For example, isolated contraction of the lon-
gitudinal muscles would be expected to shorten and
thicken the tongue. However, contraction of a muscle ori-
ented in the cross-sectional plane of the tongue, such as
the vertical and transverse (V/T) muscles, thins, and
lengthens the tongue. If both groups contract simultane-
ously, they work against each other and the tongue
adopts a rigid position. If the longitudinal muscles on
one side are more active the tongue bends to that side.
The whole tongue can move as a unit, change its
shape to elongate or shorten, or articulate its different
parts. Movement of the entire tongue posteriorly is
called retrusion while anterior movement is called pro-
trusion. Curving the tongue tip superiorly is called dor-
soflexion while inferior curving is called ventroflexion.
Movement of the tongue superiorly is called elevation
and inferiorly is called depression. Simultaneous depres-
sion of the tongue body with elevation of the base is
called retroflexion.
Moreover, the anatomy and physiology of the human
tongue is more complex than that of other species.
Clearly the human tongue performs unique movements
during speech and swallowing; however, the anatomical
specializations that underlie these unique tongue move-
ments are almost completely unknown. All of the named
tongue muscles can be identified as discrete entities in
some region of the tongue. However, in other parts of
HUMAN TONGUE MUSCLES 1103
the tongue each muscle separates into smaller muscle fas-
cicles that interweave with those other tongue muscles.
The result is that in large parts of the tongue, muscle fas-
cicles from two or more muscles are indistinguishable.
On the basis of what is available in the literature it is
difficult for new investigators to understand the 3D
anatomy of human tongue muscles and almost impossi-
ble for them to identify individual muscles in histological
sections. The most referenced study on the internal
anatomy of the human tongue is that of Abd-El Malek
(1938b). Abd-El-Marek’s written descriptions of the
muscles and fascial planes of the human tongue are
highly detailed and include seven photographs of tongue
coronal sections at anterior to posterior levels. Although
these photographs still are the best depiction of human
tongue anatomy their resolution is poor. More recent
publications by Miyawaki (1974), Takemoto (2001), and
Miller et al., (2002) are all valuable contributions but still
do not convey the 3D complexity of the tongue muscles.
The objective of this study was to provide graphical
depictions of the human tongue that present its complex
anatomy in a simplified manner. The first aim was to
construct a 3D model of the human tongue that shows
the position of each muscle. The second aim was to pro-
vide a set of serial reconstructions of the human tongue
in all three of the main anatomical axes: axial, coronal,
and sagittal. The third aim was to provide an easily
understandable explanation of tongue anatomy based on
these graphical images. The intent was not necessarily
to introduce new anatomical information on the human
tongue, although some novel observations are reported.
Instead the goal was to report a relatively complete but
easily understood study of the 3D anatomy of the human
tongue. The lack of this information in the literature
appears to be the main obstacle for researchers and
clinicians. Hopefully, this report will be of value to them
and advance the study of normal and abnormal tongue
anatomy and physiology.
MATERIALS AND METHODS
Visible Human Project (http://nlm.nih.gov)
The Visible Human (VH) Project was an initiative of
the National Library of Medicine that began in 1986 and
is still continuing. The aim of the project was to estab-
lish a database of normal male and female human anat-
omy. One male (age 37) and one female (age 59) were
embedded in ice and completely serially sectioned in the
axial plane. The various anatomical planes are illus-
trated in Fig. 1: the axial plane is perpendicular to the
axis of the body and was the original plane of sectioning
of the VH; the sagittal plane passes through the midline
of the tongue and bisects into two symmetrical
Fig. 1. The anatomical planes in the Visible Human: sagittal (left),
axial (middle), and coronal (right). The Visible Human Male and Female
were frozen in a block of ice and serially sectioned in the axial plane,
the cross-sectional plane that is perpendicular to the long axis of the
body. Each section was digitally photographed at high resolution. The
background photograph of this figure is part of section #1184 of the
Visible Human Male converted to grayscale. This section passes
through the tongue, which is in the middle of the photo. The midline
septum of the tongue is marked by an arrow and the transverse
muscle passes laterally from this septum throughout the length of the
tongue. As the digital photographs were taken at high resolution the
area of the tongue can be magnified and cropped from the original
image and still show reasonable detail. As the sections from the Visi-
ble Humans were precisely cut at constant intervals (1 mm for the
male and 0.33 mm for the female) the serial axial images can be
reconstructed into any other plane by computer programs. An exam-
ple of reconstructed tongue images are shown for the sagittal plane
and coronal plane. A, anterior; S, superior.
1104 SANDERS AND MU
hemitongues; the coronal plane is perpendicular to the
long axis of the tongue.
The male was sectioned at 1 mm intervals resulting
in a total of 1,871 sections. Each cryosection was photo-
graphed at a resolution of 2,048 31,216 pixels with a
color depth of 24 bytes, resulting in a data file of 7.5
megabytes for each section (Fig. 1). For the female the
section interval was decreased to 0.33 mm. This interval
equals the pixel size in the X- and Y-axis so that the X-,
Y-, and Z-planes were equal, making it easier to develop
3D reconstructions. There are 5,189 images in the visi-
ble female data set, and the total amount of data exceeds
40 gigabytes. In August 2000 a second data set of higher
resolution digital photographs was released for the
human male. Each is a 70 mm photograph digitized at
4,096 32,700 pixels in RAW data format with a total
file size of 31.8 megabytes each.
The images from the VH data have the advantages
that the original axial photographs can be reconstructed
by computer programs into other anatomical planes.
Therefore, the same specimen can be examined with se-
rial sections from many different anatomical planes of
section (Fig. 1). This has proven to be uniquely valuable,
as the extremely complex muscular anatomy of the
tongue requires these multiple views. An additional
advantage of the VH data is that it originates from
intact cadavers so the tongues are in their natural, in
vivo position. This advantage is easy to underestimate;
however, normal histological processing of excised
tongues introduces many artifacts that further compli-
cate the interpretation of the images.
Some computer science departments have developed
software specifically to reconstruct the VH data in vari-
ous forms. One of the most useful for studying the
tongue is the Visible Human Slice and Surface Viewer
(VHSSV) located at the Computer Science Department
of the Ecole Polytec Federale De Lausanne in Lausanne
Switzerland (Director, Professor R.D. Hersch). By access-
ing their internet site (http://visiblehuman.epfl.ch/) the
user can retrieve reconstructed images from the VH
data sets in any anatomical plane. Using the VHSSV,
total reconstructions of the male and female tongue
were retrieved in the coronal, sagittal, and axial planes.
The clearest tongue data set is that of the female, and
the frontal serial section data was used for the 3D com-
puter reconstruction. Unfortunately, the male has multi-
ple teeth missing from the left side and the tongue is
deformed in this area.
Three-Dimensional Tongue Model: Surfdriver
(http://www.surfdriver.com)
Tongue anatomy is inherently 3D and it is difficult to
understand this anatomy from 3D images alone. This
structure is best communicated by 3D models, and to our
knowledge there are no 3D models available for the
human tongue. Until recently, 3D reconstructions
required the use of expensive software running on speci-
alized computer workstations. A recently released pro-
gram, Surfdriver (Developed at the University of Hawaii
and the University of Alberta by Drs Scott Lazanoff and
David Moody, respectively) allows construction of 3D
models from serial sections on a personal computer. The
3D models could provide valuable anatomical data on the
individual tongue muscles, which are useful not only for
researchers, but also for clinicians and students.
The 3D model of the tongue was reconstructed from
70 equally spaced digital coronal sections of the visible
female data set obtained from the VHSSV (Fig. 2). All
images were in jpg format and in direct alignment. Each
image was opened in Surfdriver and the regions of inter-
est (ROI) were manually outlined with a closed polygon.
As the cross-sectional perimeters of each tongue muscle
was manually traced, the reproducibility of the method
was tested. Each of the tongue muscles or muscle groups
was outlined by two investigators, respectively. We
revealed a high interobserver agreement (>96%) for de-
marcation of each muscle or muscle group on the cross-
sections of the VHs. After entering all outlines, each
ROI was individually reconstructed into a 3D object. The
ROIs were the mandible, the tongue mucosa, the supe-
rior longitudinal (SL) muscle, IL, geniohyoid (GH), GG,
HG, and styloglossus (SG) muscles, and the midline fas-
cial septum of the tongue. The V and T muscles were
outlined as a single unit (V/T) as they were too closely
intertwined to be outlined separately. Overlapping vol-
umes are difficult to trace and display so that the model
reflects those areas where a muscle exists as a distinct
entity. Therefore, areas of overlap between muscle
groups are ignored, as it would make the model overly
complex. For example, the GG muscle has fascicles that
pass through practically every other muscle. A different
color was given to each muscle to easily differentiate
between them (Fig. 2).
The Surfdriver software has several features that are
useful for manipulating the image to highlight different
aspects of tongue structure. One feature is the ability to
render any structure invisible, thereby allowing visual-
ization of interior structures. The amount of translu-
cency can be adjusted so that an object such as the
surface of the tongue can be retained as a ghost outline
that allows the muscles to be seen in their normal posi-
tion relative to this key landmark. Another feature is
that the model can be rotated into any position, magni-
fied, or reduced, or has the surface of objects replaced
with various textures or colors. One disadvantage of the
model is that it is difficult to render muscles with the
orientation of the muscle fibers displayed on the surface.
Thick Human Tongue Sections
The images from the VH are almost too clear and
properly aligned to be used as a guide to histological sec-
tions, which lack clear landmarks and are almost always
skewed and misshapen. A depiction of anatomy interme-
diate between the VH and histological sections was
obtained from thick tongue sections. Three tongues
obtained from autopsies (2 males, ages 55 and 75, and 1
female, age 60) performed at the Mount Sinai Hospital
were fixed in formalin and sectioned in the coronal plane
at thicknesses from 1 to 3 mm on a rotary microtome.
The thick sections were processed as whole mounts by
acetylcholinesterase staining as they were initially pre-
pared to study motor endplate locations within the
muscles. Although the staining was unsuccessful the
process rendered the thick sections translucent. When
examined by transilluminated light these sections add a
dimension of depth that provides some helpful 3D infor-
mation. Moreover, the sections could be examined by
HUMAN TONGUE MUSCLES 1105
dissecting microscopes at higher resolutions than the
photographs from the VH data. In addition the sections
have some of the artifact that is present to a much
greater extent in histological sections: although they
were carefully aligned during sectioning, there is some
obliquity introduced during the sectioning process so
that one side is slightly more anterior than the other. In
some parts of the tongue this introduces surprisingly
large anatomical asymmetries. In addition to the asym-
metrical artifacts introduced during sectioning, the sec-
tions unfold to some degree. In the dorsum of the tongue
a large connective tissue boundary keeps the muscles in
their original position. However, in the inferior tongue,
around where the GG muscle enters the tongue, the
muscles are not as well restrained and their position
shifts relative to their original in vivo locations.
These technical issues were evident in histologic sec-
tions. The sections were between 10 and 50 lm in thick-
ness and were more malleable than the thick sections
described above. Large technical artifacts were present
despite great care in orienting and mounting the speci-
mens correctly on the microtome.
RESULTS AND DISCUSSION
The main goal of this study was to provide a guide to
the muscular anatomy of the human tongue. Using
images of the tongue from the VH Project (Fig. 1) a 3D
model of the tongue and its muscles was constructed
(Fig. 2). Below is a review of terminology regarding the
tongue’s anatomy and movements (Figs. 3–5), followed
by descriptions of the shape and position of each muscle
from the 3D model (Figs. 2–4) and from serial sections
in the coronal plane (Fig. 6), sagittal plane (Fig. 7), and
axial plane (Fig. 8).
Description of Tongue Muscle Anatomy
The anatomy of each tongue muscle will be described
from anterior to posterior in serial coronal sections. The
3D rendering of each muscle is shown in Figs. 3 and 4.
Serial coronal sections of the tongue are in Fig. 6. Fig-
ures 7 and 8 show serial sections from the sagittal and
axial planes, respectively.
Some intrinsic tongue muscles overlap so extensively
that they are sometimes best considered as single entity
rather than separate muscles. The most important
example is the T/V muscles where we term the combined
entity the T/V. A second important example is in the in-
ferior aspect of the anterior tongue where four of the
longitudinally oriented tongue muscles (IL, GG, HG, and
SG) interdigitate and become indistinguishable. For con-
venience we have named this the combined longitudinal
muscle (CL).
Fig. 2. Three-dimensional model of the human tongue. (A) Anterior
view of the 3D model of human tongue and mandible. (B) Lateral view
of 3D model with the surface removed. Note that each muscle is ren-
dered in a different color and the legend for each tongue muscle color
is shown above the tongue. SG, styloglossus; HG, hyoglossus; SL,
Superior longitudinal; TV, transverse/vertical; IL, inferior longitudinal;
GG, genioglossus. (C) Lateral view of the 3D model with the thee
boundaries shown between the base, body, and blade. (D) A mid-sag-
ittal view of the Visible Human showing the approximate boundaries
between base, body, and blade, and each muscle marked with its
abbreviation in the muscle’s color in the 3D model.
1106 SANDERS AND MU
Extrinsic Tongue Muscles
Genioglossus (GG) muscle (Figs. 2, 3G–I, 4D, 6–
8). Although it is absent from the tongue blade the GG
muscle’s large volume, central position, and its passage
though most of the intrinsic muscles makes the GG mus-
cle the most important landmark in the coronal plane. As
the GG muscle fascicles are oriented at different angles,
the degree to which its fascicles appear vertical or hori-
zontal indicates whether a coronal section is from the an-
terior or posterior aspect of the tongue, respectively.
The GG are paired muscles that originate from the
inner midline of the mandible and fan out in a 90arc.
All GG muscle fascicles enter the intrinsic tongue and
pass between fascicles of the T/V and SL muscles and
terminate in the connective tissue of the dorsum. As
such the GG actually constitutes the V muscle in these
areas. The lateral fascicles of the oblique GG do not pass
directly vertical but course slightly obliquely, and this
oblique orientation increases in the tongue base. When
it is relevant to distinguish the two parts of the GG, the
part of the GG outside the tongue we term the extrinsic
GG, and the part within the tongue the intrinsic GG.
Although the intrinsic and extrinsic components of the
GG appear to be continuous, the components are inner-
vated by different branches of the hypoglossal nerve and
may actually be composed of separate muscle fibers
arranged in series.
Anteriorly the GG is thin and its fascicles are verti-
cally oriented. The most anterior fascicles compose the
frenulum, an external landmark that defines the border
Fig. 3. This figure shows the positions of the intrinsic and extrinsic
muscles in the tongue and also demonstrates the options available for
presenting anatomical data with the 3D model. (A) An oblique frontal
view of the complete tongue model including the mandible. (B) The
tongue is now seen in the same orientation as A and the mandible is
made transparent. (C) The tongue surface is made translucent so that
the muscles inside the tongue can be seen. The amount of translu-
cency can be adjusted. The ghost outline of the tongue surface serves
as a reference for the internal muscles, although it does obscure them
to some extent. (D) The tongue surface is made transparent. Now the
tongue muscles can be clearly seen. In this orientation the superior
longitudinal (SL) muscle drapes over the transverse/vertical (T/V) mus-
cle group. (E) The SL muscle is made translucent. (F) As the muscles
all overlap in E the view is still not optimum so that the model is
rotated to an oblique inferior view and the transparent mandible is
restored to aid in orientation. (G) The extrinsic muscles are seen from
above through a translucent surface. (H) The tongue surface is
removed and the muscles are clearly seen. (I) Rotation of the model to
a frontal view helps to show the spatial relationship between the
muscles. GG, genioglossus muscle; HG, hyoglossus muscle; IL, infe-
rior longitudinal muscle; SG, styloglossus muscle.
HUMAN TONGUE MUSCLES 1107
between the tongue blade and the tongue body (Figs. 6–
8). In coronal sections the anterior GG muscle is narrow,
its fascicles are thin and they are sectioned lengthwise.
In sections from more posterior levels the entire GG
muscle as well as its fascicles become wider and change
their orientation from vertical to oblique (Fig. 8).
The most posterior part of the GG has long been con-
sidered a separate muscular compartment called the
horizontal, and it is separated from the remaining
oblique GG by a thin layer of connective tissue (Doran
and Baggett, 1972). The horizontal compartment is ana-
tomically simple, it originates from the mandible and
courses directly posterior to insert into the hyoid bone or
connective tissue above it. The horizontal compartment
is believed to function largely in the respiratory actions
of the tongue, moving the hyoid and base of tongue ante-
riorly during inspiration to dilate the airway (Mu and
Sanders, 2000).
The oblique compartment of the GG is quite different
from the horizontal compartment (Doran and Baggett,
1972; Mu and Sanders, 1999, 2000, 2010). The oblique
GG has two parallel rows of large distinct muscle fas-
cicles. These fascicles fan out from their origin on the
mandible to insert throughout most of the length of the
tongue. The oblique GG is thin anteriorly and becomes
progressively wider toward the posterior aspect of the
tongue. Around the centerline of the tongue the fascicles
of the GG pass directly between the fascicles of the T
and SL muscles to insert into the dorsal mucosa of the
tongue.
The GG is surrounded by the paramedian septum and
is bordered laterally by the IL and HG muscles.
The GG is the muscle that is the most different in
humans relative to other mammals. In dogs the GG is a
thin sheet that is restricted to the midline of the tongue
(Mu and Sanders, 1999, 2000). In humans the GG is
much larger and has expanded its insertion laterally,
especially in the tongue base. The main role ascribed to
the GG is tongue protrusion, caused by the horizontal
compartment and the posterior fascicles of the oblique
compartment (Mu and Sanders, 2010). Additional actions
believed to be performed by the GG are: depression of
the body of the tongue by the more vertically oriented
fascicles in the middle of the oblique GG; ventroflexion
and possibly retrusion of the tongue tip by the most ante-
rior muscle fascicles. In addition to these actions, the
insertion of the GG around the midline of the tongue dor-
sum is believed to cause the concave cross-sectional
shape of the superior tongue surface that is a distinctive
feature of speech and swallowing movements.
Fig. 4. Muscles of the human tongue. (A) The superior longitudinal
(SL) muscle is the only unpaired muscle of the tongue, which spans
the length of the tongue just beneath the mucosa of its superior sur-
face. (B) The inferior longitudinal (IL) muscle spans the length of the
tongue just above the mucosa of its inferior surface. (C) The trans-
verse and vertical (T/V) muscles. The T muscle connects the medial
septum to the lateral aspect of the tongue. The V muscle connects
the inferior surface to the superior surface. (D) The genioglossus (GG)
muscle is midline muscle, which originates from the posterior surface
of the mandible. (E) The styloglossus (SG) muscle originates from the
styloid processes and insert along the inferior-lateral margins of the
tongue. (F) The hyoglossus (HG) muscle originates from the hyoid
bone and also insert into the inferior-lateral margins of the tongue. The
muscles are all rendered as separate objects for the sake of clarity,
but in reality there is extensive overlap. One example is that the GG
muscle becomes the vertical muscle in the medial third of the tongue.
The other example is that the T/V muscles are rendered as a single
object.
1108 SANDERS AND MU
Hyoglossus (HG) muscle (Figs. 2B, 3G–I, 4F, 6B,
7, 8). The HG originates from the body and greater
cornu of the hyoid bone. The HG is bordered by the GG
and IL muscle medially and the SG muscle laterally. It is
thin planar muscle near its origin but separates into dis-
tinct fascicles that fan out and insert along the length of
the tongue. The most posterior fascicles of the HG course
superiorly and medially across the posterior surface of
tongue base and appear to be continuous with the origin of
some of the SL muscle. The middle fascicles of the HG
course obliquely superiorly and insert on the lateral edge
of the tongue. These fascicles appear continuous with the
insertion of some fascicles from the T and GG muscles. The
anterior fascicles of the HG course anteriorly along the lat-
eral edge of the tongue to insert into the CL, which in turn
inserts into the tongue cap. The action of the HG is retru-
sion and depression of the lateral margin of the tongue.
Styloglossus (SG) muscle (Figs. 2B, 3G–I, 4E,
6B, 8). The SG originates from the styloid process and
stylomandibular ligament and is the most lateral of the
tongue muscles. It appears to have two components: a
smaller posterior compartment merges into and possibly
passes through the lateral surface of the HG muscle at
the tongue base; and a larger anterior compartment
courses along the lateral aspect of the and merges with
the IL muscle and other muscles to form the CL (Figs. 7
and 8). The SG is thin and comparatively small and is
often difficult to distinquish from the larger HG muscle.
The action of the SG is retrusion and elevation of the
lateral margin of the tongue.
Palatoglossus, glossopharyngeus, chondroglos-
sus muscles. At least three small muscles (PG, GP,
and CG) insert into lateral margin of the tongue other
than the SG and HG. These muscles are generally not
thought to significantly contribute to tongue movement
(Pernkopf Anatomy, 1989) and were not included in the
3D model. In Pernkopf Anatomy (1989), these muscles
are not considered to be extrinsic tongue muscles or
even as distinct muscles at all and will only be briefly
mentioned.
Fig. 5. Movements of the human tongue. The human tongue is ca-
pable of changing its shape in multiple ways; however, some basic
patterns are often described and are a source of confusion. The upper
left corner shows the 3D model in relation to the mandible and the
upper right corner reproduces this is a simpler schematic form. This is
the rest or neutral position and is the reference for all the movements
described. When the tongue is moved posterior it is said to retract
and the various ways that this can be done are shown in column 1.
Retrusion is the posterior movement of the whole tongue with little
change in shape. Retrusion is probably performed by extrinsic
muscles, specifically the hyoglossus (HG), and styloglossus (SG).
However, the appearance of retraction can be obtained by changing
tongue shape so that the blade shortens. This shortening is likely due
to the action of the muscles that are oriented lengthwise, primarily the
superior (SL) and inferior longitudinal (IL) muscles. As the tongue’s vol-
ume is constant shortening causes the tongue to become thicker. In
actual tongue movements retraction is usually cause by combining
retrusion with shortening. When the tongue moves anteriorly in the
mouth is said to protrude (column 2). Anterior movement can be done
by moving the entire tongue forward (protrusion), which is most likely
causes by the posterior fascicles of the genioglossus (GG) muscle.
However, a similar appearance can be obtained by elongating the
tongue. Elongation is caused by contraction of the muscles oriented
in the coronal plane, specifically the vertical and transverse (T/V)
muscles. In column 3 basic bending motions of the tongue are shown.
Dorsiflexion is the superior bending of the tongue tip. This is likely
caused by contraction of the SL muscle. Ventroflexion is the inferior
bending of the tongue tip, most likely caused by IL and/or combined
longitudinal muscle contractions. Retroflexion is the superior move-
ment of the tongue base. This movement combines the superior and
posterior pull of the SG muscle aided by depression of the midtongue
by vertically oriented muscle fascicles of the GG.
HUMAN TONGUE MUSCLES 1109
Fig. 6. Continued
1110 SANDERS AND MU
The PG muscle, also called the GP muscle, arises from
the anterior surface of the soft palate, courses inferiorly
to compose the palatopharyngeal arch, and inserts into
the lateral margin of the tongue. It originates from the
aponeurosis of the soft palate and inserts into the lateral
margin of the tongue just medial to the SG muscle.
Some of its fibers spreading over the dorsum, and others
passing deeply into the substance of the organ to inter-
mingle with the T muscle.
The GP muscle is the most inferior part of the SPC
muscle, and it inserts medial to the PG muscle.
The CG muscle is sometimes described as a part of
the HG muscle, but is separated from it by a lateral fas-
cicle of the GG muscle that passes to the side of the
pharynx. It arises from the medial side of the lesser
cornu and passes directly upward to blend with the
intrinsic muscular fibers of the tongue, between the HG
and GG muscles.
Intrinsic Tongue Muscles
Superior longitudinal (SL) muscle (Figs. 2B,
D; 3E, F; 4A, 6–8). The SL muscle spans the length
of the tongue just beneath the mucosa of the superior
surface of the tongue. It is well demarcated in coronal
sections as it is separated from the T muscle inferiorly
by a thin layer of connective tissue. Grossly the SL
appears as to be a muscular sheet that is thickest in the
posterior tongue body and thins to insert into the tongue
cap anteriorly, and connective tissue and possibly hyoid
bone posteriorly. On closer examination the SL is com-
posed of many individual fascicles oriented longitudi-
nally (Mu and Sanders, 1999, 2010). Between these
fascicles the vertical muscle fascicles pass to reach the
connective tissue of the tongue dorsum. The SL is dis-
tinctive for its high content of connective tissue that
appears to couple it biomechanically to the connective
tissue of the tongue dorsum. The SL is thick in the pos-
terior body of the tongue but thins anteriorly where it
inserts into the cap and also posteriorly in the tongue
base. Contraction of the SL shortens the tongue and also
dorsiflexes the tip of the tongue. The SL is perhaps the
easiest muscle to identify in frontal sections.
Inferior longitudinal (IL) muscle (Figs. 2B,
3D–F, 4B, 6B, 7, 8). The IL muscle originates near
the tongue base and passes anteriorly to join the GG,
HG, and SG to form the CL. The IL appears to have two
parts: a smaller part in the tongue blade lies within the
CL and is oriented parallel to the long axis of the
tongue; the larger part originates from the hyoid and
Fig. 6. (A) Coronal sections of the tongue blade and anterior tongue
body. Human tongue muscles are seen best in the coronal plane as
most muscles of the tongue are oriented lengthwise and, except for
the tongue base, they are seen in cross section. In the left upper cor-
ner the lateral view of the 3D model is shown with the color legend for
each muscle to its right. Beneath the 3D model is a line with markers
showing the approximate location of the 12 coronal sections seen in
this figure. The 12 samples of the human tongue in the coronal plane
are arranged from anterior to posterior levels. At each level the thick
human tongue (HT) section is shown on the left and the reconstructed
images of the visible human (VH) male are shown on the right. Levels
are marked by their distance in millimeters from the tongue tip begin-
ning at 10 mm. On the right side of each specimen the muscles are
outlined with lines of the same color used for that muscle in the 3D
model. One exception is the combined longitudinal muscle (CL), which
is not present in the 3D model and is outlined in black in the sections.
Tongue blade (0–15 mm): The tongue blade extends from the tip of
the tongue to the frenulum. The anatomy within the human tongue
blade most resembles that of other mammals. Specifically, the struc-
ture is relatively simple and symmetrical. Longitudinally oriented mus-
cle fascicles line the perimeter of the tongue while the central core
contains muscle fascicles oriented in the cross-sectional plane. As
this basic pattern is present throughout the tongue blade only a single
specimen from this level is included (15 mm). Note that the thick sec-
tions is skewed such that the left side of the section is from a more
posterior level than the right and the size of the left side is therefore
larger than the right side. The superior longitudinal (SL) muscle is rela-
tively thin in the tongue blade. Below the SL the transverse and verti-
cal (TV) is quite prominent. Inferior to the TV is the CL, a combined
longitudinally oriented muscle largely formed by the inferior longitudi-
nal (IL) and styloglossus (SG). Anterior tongue body (20–35 mm): In
this study the tongue body refers to the part of the tongue extending
from the frenulum anteriorly to the sulcus terminali posteriorly. The
tongue body can be divided into an anterior half, which is shown in
this panel (20–35 mm), and a posterior half, which is seen in Fig. 6B.
The internal anatomy of the tongue body is markedly different from
the blade because of the presence of the genioglossus (GG), and the
size of the GG as well as the degree to which it is cut obliquely is
helpful in identifying the anterior–posterior level of the section. The
tongue body has a distinctive mushroom shape: the simple structure
of the tongue blade appears to be elevated and displayed by an
increasingly enlarging GG muscle. Throughout the tongue body two
rows of thick GG fascicles are seen. Anteriorly in the tongue body the
GG fascicles are vertically oriented and in coronal sections they are
cut lengthwise. The GG fascicles pass through the TV and SL to insert
into the dense connective tissue of the dorsum. In most sections the
full course of the GG is obscured by the TV but at least in the 25 mm
VH and HT sections, some of the GG fascicles can be seen for their
entire length. At progressively more posterior levels the GG muscle is
seen at more oblique angles and until it appears in cross-section at
the base of the tongue (compares level 25 mm with 50 mm). Although
a fascial plane called the paramedian septum separates the GG from
the CL, it is often difficult to find this plane in histological sections. A
good landmark is the lingual artery (red dot), which passes between
the GG and CL in the anterior tongue body, and between the GG and
the IL in the posterior tongue blade. (B) Coronal sections of the poste-
rior tongue body and tongue base. Posterior tongue body (40–50
mm): Superiorly, the SL is very sharply delineated and is thickest in
the posterior body (see 50 mm). Directly below the SL is the combined
TV. The TV is also well demarcated superiorly and inferiorly, although
it becomes more obscure laterally. In contrast to the SL, the TV is
larger in the anterior tongue body. The CL is a single mass until about
40 mm when its individual components begin to separate. The IL is
the most difficult muscle to appreciate, and is best seen as a separate
muscle at about VH sections 45–55 mm. The GG has a large distinct
fascicle in its supero-lateral margin that is easy to mistake for the IL
(white line). Tongue base (55–65 mm): The tongue base begins at the
level of the circumvallate papillae. Overall the structure of the tongue
deteriorates as the muscles divide into smaller fascicles and the
amount of fat and other soft tissue increases. A midline groove
appears in the superior surface of the tongue and progressively
enlarges until the tongue separates into two halves posteriorly. This
groove is much more pronounced in the HT sections, and may be an
artifact of intubation. The transverse muscle is largest in this area and
those of the GG and IL separate its fascicles as they pass to insert
into the tongue base. The vertical muscle is small in this region. In
contrast, the HG and SG muscles are best seen in this area as they
are sectioned close to their origins.
HUMAN TONGUE MUSCLES 1111
connective tissue and hyoid medial to the origin of the
HG muscle. The larger part courses obliquely straight
from the tongue base to the blade without following the
curvature of the tongue as the SL does. In most mam-
mals the action of the IL is tongue shortening and ven-
troflexion. In addition in the human the orientation of
the larger part seems ideal for retroflexion of the tongue
base. Interestingly, the IL is very prominent and easy to
identify in the tongues of nonhuman mammals, but is
probably the most difficult muscle to identify in coronal
sections of the human tongue.
Transverse (T) muscle (Figs. 2B, D, 3D–F, 4C,
6–8). The T muscle originates from the median septum
and course laterally. The more superior fascicles of the T
muscle pass between the fascicles of the SL to insert
into connective tissue of the lateral tongue surface. The
more inferiorly situated insert on the connective tissue
overlying the IL, HG, or CL. The T muscle is relatively
enlarged in the human in comparison to other mamma-
lian tongues and it extends further anterior and poste-
rior than the vertical muscle. The action of the
transverse is to narrow the tongue thereby simultane-
ously increasing its sagittal depth and causing elonga-
tion of the tongue body and blade.
Vertical (V) muscle (Figs. 2B, D, 3D–F, 4C, 6–
8). The V muscle is a continuation of the GG in the
medial third of the tongue. More laterally it originates
on the connective tissue overlying the IL, HG, and CL.
The V muscle fascicles pass between the fascicles of the
SL to insert into the dorsum of the tongue. The action of
the V muscle is to flatten the tongue thereby simultane-
ously increasing its width and elongating it.
SUMMARY
Human tongue anatomy, while complex, has certain
patterns that make it understandable. One helpful way
Fig. 7. Sagittal sections of the human tongue. This figure shows the
appearance of the VH male tongue in the sagittal plane beginning in
the mid sagittal plane. Subsequent sections are not evenly spaced but
were chosen for to demonstrate specific muscles. The striking aspect
of the sagittal view is the curvature of the human tongue. The GG
muscle is organized in a fan shape to insert throughout the tongue. At
the GG origin a tendon extends from the mandible to allow room for
this large muscle. Except for the horizontal GG the fascicles of the GG
appear to be of equal length. The overall organization is neat and sim-
ple: two muscle groups, the SL, and TV follow the curvature of the
tongue throughout its length. Both muscles are sharply demarcated
throughout most of their lengths. Note that the density of muscle of all
types is least in the tongue base. In the 0 mm section, the double
headed arrows mark the boundaries of the SL and TV muscles. The
SL is thickest in the posterior tongue body while the TV is thinest in
the same area. The TV depth is greatest in the tongue base but its
density is the least there. The extent of the GG is delineated by the
long curved line. The GG has two bellies, the horizontal GG (hGG)
inferiorly and the fan shaped oblique GG (oGG) superiorly. The genio-
hyoid (GH) muscle is beneath the hGG and it is difficult to separate
the two muscles. In the 5 mm section, as the sections go laterally the
GG disappears anteriorly and is progressively replaced by the CL. The
CL is partly composed by the IL which has a small medial part that is
horizontally oriented. In the 7 mm section, a lateral, larger part of the
IL is oriented more obliquely. Note that the IL does not follow the cur-
vature of the tongue. In the 12 mm section, the HG originates from
the hyoid bone and its initial course is lateral to the IL. In the 16 mm
section, we discern at least three distinct parts of the HG: (1) A small
posterior group of fascicles passes superiorly at the tongue base and
eventually merge or are continuous with fascicles of the SL muscle;
(2) The largest part of the HG inserts into the lateral edge of the
tongue; (3) A small part of the HG courses superior and anterior to
merge into the CL.
1112 SANDERS AND MU
to visualize the human tongue is that it is composed of
two basic parts. A wedge shaped GG in the midline sepa-
rates the tongue muscles into two longitudinal masses.
The easiest muscle to identify in any coronal section of
the tongue is the SL muscle. A second important land-
mark is the GG muscle, which composes the bulk of the
midtongue posterior to the frenulum. Just lateral to the
GG muscle is the paramedian septum and the lingual
artery, which separate the GG from the IL muscle. This
study introduced the novel concept of the combined lon-
gitudinal muscles, the longitudinal muscle mass located
inferiorly in the anterior half of the tongue. It was used
to describe a complex spatial relationship that has been
seldom discussed in previous studies.
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1114 SANDERS AND MU
