Hyoid bone Sternocleidomastoid Introduction of anterior triangle Sub-divisons Muscles in anterior triangle Vessels Carotid system Nerves Ansa cervicalis Lymph nodes Clinical anatomy Conclusion References

1. ANTERIOR TRIANGLE OF THE
NECK
MONIKA
Department of Public Health
Dentistry.

2. CONTENTS :
• Hyoid bone
• Sternocleidomastoid
• Introduction of anterior triangle
Sub-divisons
Muscles in anterior triangle
Vessels
Carotid system
Nerves
Ansa cervicalis
Lymph nodes
Clinical anatomy
Conclusion
References

3. HYOID BONE
• Hyoid bone is a U shaped bone
• Develops from second and third branchial arch
• Situated in anterior midline of neck between the chin
and thyroid cartilage
• At rest it lies at the level of the third cervical vertebra
behind and base of mandible

4. • It is kept in suspended position by muscles and
ligaments
• The bone consist of the central part ,two pairs of
cornua ,greater and lesser

6. STERNOCLEIDOMASTOID MUSCLE
• ORIGIN : sternal head superolateral part of the front
of the manubrium sterni
• Clavicular head :medial one third of the superior
surface of the clavicle
• Insertion :lateral surface of mastoid process,lateral
half of superior nuchal line

8. INTRODUCTION
• The anterior triangle of the neck lies between midline
of the neck and sternocleidomastoid muscle .
• BOUNDARIES
• Anteriorly by the median plane
• Posteriorly by the sternocleidomastoid muscle
• Superiorly by the base of mandible

11. • Apex of the triangle lies above manubrium sterni
• SURFACE LANDMARKS
• The mandible forms the lower jaw
• The body of the U shaped hyoid bone can be felt in
median plane .
• The thyroid cartilage of the larynx forms a sharp
protuberance in the median plane .

12. SUBDIVISIONS
• The anterior triangle is subdivided by the digastric
muscle and superior belly of omohyoid into :
• SUBMENTAL
• DIGASTRIC
• CAROTID
• MUSCULAR TRIANGLES

14. SUBMENTAL TRIANGLE
• This is a MEDIAN TRIANGLE
• BOUNDED BY:
• Laterally by DIGASTRIC MUSCLE
• Base formed by body of hyoid bone
• Apex formed by chin
• Floor is formed by right and left mylohyoid muscle and
median raphe uniting them

16. CONTENTS
• Two to four small submental lymph nodes are
situated in the superficial fascia between the anterior
bellies of digastric muscle .
• Small submental veins .

17. DIGASTRIC TRIANGLE
• BOUNDARIES
• Anteroinferiorly : anterior belly of digastric
• Posteroinferiorly : posterior belly of digastric and
stylohyoid
• Base : base of mandible and line joining the angle of
mandible to the mastoid process

19. ROOF OF DIGASTRIC TRIANGLE
• Roof is formed by :
A. skin
B. Superficial fascia containing the platysma ,cervical
branch of facial nerve and ascending branch of the
tranverse or anterior cutaneous nerve of neck
C. Deep fascia

20. FLOOR OF DIGASTRIC TRIANGLE
• The floor is formed by the mylohyoid muscle
anteriorly and by the hyoglossus posteriorly

22. CONTENTS OF DIGASTRIC TRIANGLE IN
ANTERIOR PART :
• Structures superficial to mylohyoid are :
A. Superficial part of the submandibular salivary gland
B. Submental artery
C. Mylohyoid nerves and vessels
• Structres superficial to hyoglossus
A. Submandibular salivary gland ,intermediate tendon of
digastric and stylohyoid , hypoglossal nerve

23. CONTENTS OF DIGASTRIC TRIANGLE IN
POSTERIOR PART :
• SUPERFICIAL STRUCTURES
A. Lower part of parotid gland
B. The external carotid artery before it enter parotid
gland
• Deep structures
A. The styloglossus………

24. • The stylopharyngeus , glossopharngeal nerve
• The pharngeal branch of vagus nerve, styloid process
• Deepest structure include :
 Internal carotid artery
 Internal jugular vein
 Vagus nerve

26. CAROTID TRIANGLE
• BOUNDARIES :
• Anterosuperiorly :posterior belly of digastric muscle
and the stylohyoid
• Anteroinferiorly :superior belly of omohyoid
• Posteriorly:anterior border of sternocleidomastoid

27. ROOF OF CAROTID TRIANGLE
• Skin
• Superficial fascia containing :
A. Platysma
B. Cervical branch of facial nerve
C. Tranverse cutaneous nerve of neck
• Investing layer of deep cervical fascia

28. FLOOR OF CAROTID TRIANGLE
• The middle constrictor of pharynx
• The inferior constrictor of pharynx
• Thyrohyoid membrane

30. Contents of carotid triangle :
 ARTERIES :
• The common carotid artery with the carotid sinus and
carotid body at its termination
• Internal carotid artery
• External carotid artery with its superior thyroid ,lingual,
facial, ascending pharygeal and occipital branches

31. VEINS :
• The internal jugular vein
• Common facial vein draining into internal jugular
vein
• Pharyngeal vein ends in the internal jugular vein
• Lingual vein terminates in the internal jugular vein

32. NERVES :
• The vagus run vertically downwards
• The superior laryngeal branch of the vagus dividing into
the external and internal laryngeal nerves
• The spinal accessory nerve running backwards over the
internal jugular vein
• The hypoglossal nerve running forward over the external
and internal carotid arteries

36. MUSCULAR TRIANGLE
• BOUNDARIES :
• ANTERIORLY :anterior median line of neck from hyoid
bone to sternum
• POSTEROSUPERIORLY :superior belly of omohyoid
muscle
• POSTEROINFERIORLY :anterior border of
sternocleidomastoid muscle

38. CONTENTS OF MUSCULAR TRIANGLE
• The infrahyoid muscle are the chief contents and the
muscles are :sternohyoid ,sternothyroid,thyrohyoid
and omohyoid ;also known as ribbon muscle
• Arranged in two layers :superficial and deep
• All are supplied by ventral rami of 1,2,3rd cervical
spinal nerves

39. MUSCLES IN ANTERIOR TRIANGLE
• Muscles can be grouped according to their location
relative to hyoid bone :
• Muscles superior to hyoid are classified as
suprahyoid :digastric ,stylohyoid ,mylohyoid
,geniohyoid .
• Muscles inferior to hyoid are infrahyoid muscles

41. SUPRAHYOID MUSCLE
MUSCLE ORIGIN INSERTI
ON
INNERVA
TION
FUNCTIO
N
Digastric
has two
bellies
united by
intermediat
e
tendon
Anterior
belly-
digastric
Fossa of
mandible
Posterior
belly-
mastoid
notch of
temporal
bone
Both heads
meet at
intermediat
e tendon
which
perforates
stylohyoid
and held by
fibrous
pulley to
hyoid
Anterior
belly by
nerve to
mylohyoid
Posterior
belly by
facial nerve
Depresses
mandible
when
mouth is
opened
widely
Pulls hyoid
bone
upward and
backward

44. SUPRAHYOID MUSCLE
MUSCLE ORIGIN INSERTI
ON
INNERVA
TION
FUNCTIO
N
GENIOHY
OID-short
and narrow
muscle lies
above
medial part
Inferior
mental
spine
(genial
tubercle)
Anterior
surface of
body of
hyoid bone
Branch
from
anterior
ramus of
C1,carried
along
hypoglossal
nerve
Elevates
hyoid
bone,may
depress
hyoid when
mandible is
fixed

46. MUSCLE ORIGIN INSERTIO
N
INNERVAT
ION
FUNCTIO
N
stylohyoid Posterior
surface of
styloid
process
Junction of
body and
greater cornua
of hyoid bone
Facial nerve Pulls hyoid
bone upward
in
posterosuperi
or direction
Mylohyoid-
flat triangular
muscle
Mylohyoid
line of
mandible
Posterior
fibres-body of
hyoid bone
Middle and
anterior
fibers-
medianraphe
between
mandible and
hyoid bone
Nerve to
mylohyoid
Elevates floor
of mouth in
first stage of
deglutition,ele
vates hyoid
bone

49. INFRAHYOID MUSCLE
MUSCLE ORIGIN INSERTION INNERVATIO
N
FUNCTION
sternohyoid Posterior
aspect of
sternoclavicul
ar joint and
adjacent
manubrium
sternum
Medial part of
lower border
of hyoid bone
Anterior rami
of C1 to
C3through
ansa cervicalis
Depress hyoid
bone after
swallowing
Sternothyroid Posterior
surface of
manubrium
sterni
Oblique line
on lamina of
thyroid
cartilage
Anterior rami
of C1 toC3
through ansa
cervicalis
Draws larynx
(thyroid
cartilage
)downward

51. MUSCLE ORIGIN INSERTIO
N
INNERVAT
ION
FUNCTION
Thyrohyoid Oblique line
on lamina of
thyroid
cartilage
Greater horn
and adjacent
aspect of body
of hyoid bone
C1 carried
along
hypoglossal
nerve
Depresses
hyoid bone
but when
hyoid bone is
fixed raises
larynx
Omohyoid:
It has inferior
belly,common
tendon,superi
or belly
Superior
border of
scapula
medial to
suprascapular
notch
Lower border
of body of
hyoid bone
just lateral to
attachment of
sternohyoid
Anterior rami
of C1 to C3
through ansa
cervicalis
Depress and
fixes hyoid
bone

53. Vessels in anterior triangle
• Passing through the anterior triangle of the neck are
common carotid arteries and branches , the external
and internal carotid arteries . These vessels supply all
structures of the head and neck
• Associated with this arterial system are internal
jugular vein and its tributaries .

54. Carotid system
• Right common carotid artery originates from the
brachiocephalic trunk immediately posterior to right
sternoclavicular joint and is entirely in the neck
throughout its course
• Left common carotid artery begins in the thorax as a
direct branch of the arch of aorta and passes superiorly to
enter the neck near the left sternoclavicular joint

56. • Both right and left common carotid artery ascend
through the neck just lateral to trachea and
oesophagus and artery runs upwards within the
carotid sheath
• At the level of upper border of thyroid cartilage
,artery ends by dividing into external and internal
carotid arteries

57. • At the bifurcation the common carotid artery and the
beginning of the internal carotid are dilated
• This dilation is the carotid sinus and contain receptors
that monitor changes in blood pressure and are
innervated by a branch of glossopharyngeal nerve
• Another accumulation of receptors in the area of
bifurcation is responsible for detecting changes in
blood chemistry primarily oxygen-carotid body

59. • The carotid body is innervated by branches from both
the glossopharyngeal and vagus

61. INTERNAL CAROTID ARTERIES
• After its origin the internal carotid artery ascends
towards base of skull
• It gives off no branches in the neck
• It supplies the cerebral hemisphere ,the eyes and the
contents of the orbit and the forehead

62. External Carotid Arteries
• It is the terminal branches of the common carotid
artery
• It lies anterior to the internal carotid artery and is the
chief artery supply to structures in the front of neck
and in the face

63. **

64. • ANTERIOR:
a) Superior thyroid
b) Lingual
c) Facial
• POSTERIOR:
a) Occipital
b) Posterior auricular

65. • MEDIAL
a) Ascending pharyngeal
• TERMINAL
a) Maxillary
b) Superficial temporal

67. SUPERIOR THYROID ARTERY
• It is the first branch
• It arises from the external carotid artery just below the
level of the greater cornua of the hyoid bone and passes
deep to infrahyoid muscle to reach upper pole of thyroid
gland
• Its relationship to the external laryngeal nerve which
supplies the cricothyroid muscle is important to surgeon
during thyroid surgery

68. • The superior thyroid artery and external laryngeal nerve
are close to each other higher up but diverge slightly near
the gland
• To avoid injury to the nerve the superior thyroid artery is
ligated as near to the gland as possible

69. LINGUALARTERY
• The lingual artery arises from the external carotid
artery opposite the tip of the greater cornua of hyoid
bone
• Its course is divided into three parts by hyoglossus
muscle

70. • The first part lies in carotid triangle, the characteristic
upward loop which is crossed by hypoglossal nerve .The
lingual loop permits free movements of the hyoid bone
• The second part lies deep to the hyoglossus along the upper
border of hyoid bone
• The third part is called arteria profounda linguae or deep
lingual artery
• During surgical removal of tongue the first part of artery is
ligated before it gives any branch to the tongue or to tonsil

71. Facial artery
• The facial artery arises from the external carotid just
above the tip of the greater cornua of hyoid bone
• It runs upwards first in the neck as cervical and then
on the face as facial part
• The course of artery in both places is tortuous

72. • The tortuosity in the neck allows free movements of the
pharynx
• On the face it allows free movement of the mandible,lips
and the cheek during mastication and during various
expressions
• The artery escapes traction and pressure during these
movements

73. OCCIPITALARTERY
• The occipital artery arises from the posterior aspect of
the external carotid artery opposite the origin of the
facial artery
• In carotid triangle the artery gives two
sternocleidomastoid branches
• The upper branch accompanies accessory nerve and
lower branch near the origin of occipital artery

74. Posterior auricular artery
• The posterior auricular artery arises from the
posterior aspect of the external carotid just above the
posterior belly of the digastric
• It supplies the back of the auricle,skin over mastoid
process and over the back of the scalp
• It is cut in incisions for mastoid operations

75. Ascending pharyngeal artery
• It is a small branch that arises from the medial side of
the external carotid artery
• It runs vertically upwards between the side wall of
the pharynx and the tonsil ,medial wall of the middle
ear and the auditory tube

76. Maxillary artery
• This is the largest terminal branch of the external
carotid artery
• It begins behind the neck of the mandible under cover
of the parotid gland continues medial to the neck of
mandible and into the infratemporal fossa and
continues through this area into pterygopalatine fossa

77. Superficial temporal artery
• It is one of the terminal branches and appears as an
upward continuation of the external carotid artery
beginning posterior to the neck of mandible it passes
anterior to the ear crosses the zygomatic process of
the temporal bone and above the point divides into
anterior and posterior branches

78. Veins
• Collecting blood from skull,brain,superficial face and
parts of neck the internal jugular vein begins as a
dilated continuation of the sigmoid sinus which is a
dural venous sinus
• The initial dilated part is refered to as the superior
bulb of jugular vein .Tributaries to each internal
jugular vein include the inferior petrosal and the
facial,lingual,pharyngeal,occipital,superior thyroid

79. NERVES IN ANTERIOR TRIANGLE
• Numerous cranial and peripheral nerves pass through
the anterior triangle of the neck to their final
destination , send braches to structures in or forming
boundaries of the anterior triangle

80. • Cranial nerves include facial , glossopharyngeal ,
vagus,accessory and hypoglossal nerves
• Spinal nerves include transverse cervical nerve from
cervical plexus and upper and lower roots of ansa
cervicalis

81. FACIAL NERVE
• After emerging from stylomastoid foramen facial
nerve gives off branches that innervate two muscle
associated with the anterior triangle :
• Posterior belly of the digastric ,stylohyoid also
innervates platysma muscle

83. Glossopharyngeal nerve
• As the glossopharyngeal nerve passes through the
area of anterior triangle of the neck it innervates the
stylopharyngeus muscle sends a branch to the carotid
sinus and supplies sensory branches to the pharynx

85. Vagus nerve
Branches of the vagus nerve as it passes through
anterior triangle of the neck include a motor branch to
the pharynx , a branch to the carotid body ,superior
laryngeal nerve which divides into external and
laryngeal branches and possibly a cardiac branch

87. Accessory nerve
• The accessory nerve gives off no branches as it
passes through the anterior triangle of the neck

88. Hypoglossal nerve
• Hypoglossal nerve which supplies the tongue does
not give off any branches as it passes through the
anterior triangle of neck

90. TRANSCERVICAL NERVE
• It is a branch of the cervical plexus arising from the
anterior rami of cervical nerves C2 to C3
• It continues across the neck and provides cutaneous
innervation to the area

92. Ansa cervicalis or Ansa hypoglossi
• It is a thin nerve loop that lies embedded in the
anterior wall of carotid sheath over the lower part of
larynx and supplies the infrahyoid muscle
• It is formed by a superior and an inferior root
• The superior root is continuation of the descending
branch of hypoglossal nerve ,fibers are derived from
1st cervical nerve

93. • The inferior root or descending cervical nerve is derived
from second and third cervical spinal nerve
• As this root descends it winds round the internal jugular
vein then contiues anteroinferiorly to join the superior
root in front of the common carotid artery
• DISTRIBUTION:superior root :to superior belly of
omohyoid ,upper parts of the sternohyoid and
sternothyroid muscle

95. • Ansa cervicalis gives off branches that innervate the
inferior belly of omohyoid and the lower parts of the
sternohyoid, sternothyroid muscles

96. Lymph nodes
• the deep cervical lymph nodes are situated along the
internal jugular vein and include the jugulodigastric
node,anteroinferior group below posterior belly of
digastric between angle of mandible and the anterior
border of the sternocleidomastoid main node draining
tonsil

97. • The jugulo-omohyoid node belongs to posteroinferior
group,lies above intermediate tendon of omohyoid main
lymph node draining the tongue
• Submental nodes :drain lymph from tip of tongue and
anterior part of floor of the mouth
• Submandibular lymph nodes :it is clinically important
because of their wide area of drainage ,nodes lie beneath
the deep cervical fascia, to name a few centre of
forehead ,nose,eye,upper and lower lip,tongue etc.

99. FEW STRUCTURE PRESENT IN MIDLINE
OF NECK
• The thyroid gland and parathyroid gland are
endocrine gland positioned anteriorly in the neck
• The thyroid gland is a large unpaired gland while
parathyroid glands ,four in number are on the
posterior surface of the thyroid gland
• Thyroid gland consist of two lobes and isthmus that
connects the lateral lobes

101. • Arterial supply by superior thyroid artery and inferior
thyroid artery
• Venous drainage superior thyroid vein ,middle and
inferior thyroid vein
• CLINICAL ASPECT:
• Commonest pathology is multinodular goitre may need
surgical excision

102. • A thyroidectomy is a relatively common surgical
procedure .
• This surgical procedure is usually carried out for benign
diseases such as multinodular goitre .

103. CLINICAL ANATOMY
• The carotid sinus is richly supplied by nerves ,in
some persons ,the sinus may be hypersensitive ,in
such persons sudden rotation of the head may cause
slowing of heart,called as carotid sinus syndrome
• The supraventricular tachycardia may be controlled
by carotid sinus massage due to inhibitory effects of
vagus

104. • The jugular venous pulse is an important clinical sign that
enables physician to asses the venous pressure and
waveform and is a reflection of the functioning of the
right side of heart
• In Ludwigs angina swelling is within the mouth as well as
chin
• Cut throat wounds are most commonly situated just above
or just below the hyoid bone

105. • The common anterior midline swellings of the neck are:
a) Enlarged submental lymph nodes and sublingual
dermoid in the submental region
b) Thyroglossal cyst and inflamed subhyoid bursa just
below hyoid bone
c) Goitre ,carcinoma of larynx and enlarged lymph nodes
in the suprasternal region

106. CONCLUSION
The anterior triangle of neck is the most important
triangle of the neck because of the regional location of
major structures ,structures can be identified as being
within a specific subdivision or passing through several
subdivisions while traversing the region

107. • References
GRAY’S ANATOMY SECOND EDITION
,RICHARD.L.DRAKE
HUMAN’S ANATOMY ,B.D.CHAURASIA’S FIFTH
EDITION,VOLUME 3
NETTER’S HUMAN ATLAS
www.elsevierhealth.com