ANTERIOR
TRIANGLE OF
NECK
ANTERIOR REGION OF NECK
The triangular area on
the front of the neck
between the two
sternocleidomastoid
muscles is called
anterior region of the
neck.
BORDERS:
Above - lower border of the body of mandible and
line extending on either side from the angle of the
mandible to the mastoid process.
Below - Suprasternal notch.
The anterior region of the
neck is divided by the
anterior median line
(extending from
symphysis menti to the
jugular notch) into two
anterior triangles of the
neck.
ANTERIOR
TRIANGLE
OF NECK
ANTERIOR TRIANGLE OF NECK
The anterior triangle of
the neck is a large
triangular space
on each side of the neck,
in front of
sternocleidomastoid.
Apex : directed
downwards
Base : directed upwards
BOUNDARIES:
Anterior: Anterior median line of the neck.
Posterior: Anterior border of the
sternocleidomastoid muscle.
Base: Lower border of the body of mandible
and a line extending from the angle of
mandible to the mastoid process.
Apex: Suprasternal
notch at the meeting
point between anterior
border of
sternocleidomastoid and
anterior median line.
Roof: Investing layer of
deep cervical fascia.
DIVISIONS OF ANTERIOR TRIANGLE OF NECK
The Anterior triangle has been subdivided, by the Digastric
muscle and superior belly of Omohyoid muscle, into :
• SUBMENTAL TRIANGLE
• DIGASTRIC (Submandibular)
TRIANGLE
• CAROTID TRIANGLE
• MUSCULAR TRIANGLE
DIGASTRIC MUSCLE
OMOHYOID
MUSCLE
SUBMENTAL TRIANGLE
SUBMENTAL TRIANGLE
It is actually a
median triangle
on the front of
neck below the
chin and above
the hyoid bone
BOUNDARIES:
On each side: Anterior belly of digastric
muscle.
Base: Body of Hyoid bone.
Apex: Chin or symphysis menti
Floor: by two Mylohyoid muscles
Roof: Investing layer of Deep Cervical Fascia
CONTENTS:
• Submental lymph
nodes (3 or 4 in
number)
• Submental veins
• Anterior jugular veins.
CLINICAL CORRELATION:
• Infections of floor of mouth, tip of tongue, and
incisor teeth cause painful enlargement of
submental lymph nodes because lymph from
these structures is drained into these nodes
DIGASTRIC TRIANGLE
DIGASTRIC (Submandibular) TRIANGLE
It is located between the
two bellies of the Digastric
muscle and below the base
of the mandible.
BOUNDARIES:
Anteroinferiorly: Anterior belly of digastric muscle.
Posteroinferiorly: Posterior belly of digastric muscle,
Stylohyoid muscle.
Base: Base of the mandible and
Imaginary line joining the angle of the
mandible to the mastoid process.
Apex: by Intermediate tendon of the digastric muscle.
Roof: by Investing layer of deep cervical fascia.
In the superficial
fascia over the roof
lies Platysma, cervical
branch of Facial
nerve, and ascending
branch of Transverse
cervical nerve.
Floor:
by Mylohyoid (anteriorly),
Hyoglossus, and
small part of the Middle
constrictor (posteriorly).
CONTENTS:
The digastric triangle is subdivided into anterior
and posterior parts by the stylomandibular
ligament. The posterior part of the triangle is
continuous above with the parotid region.
Contents of Anterior part of Triangle:
1. Submandibular salivary gland.
2. Submandibular lymph nodes.
3. Hypoglossal nerve.
4. Facial vein (lies superficial to the gland).
5. Facial artery (lies deep to the gland).
6. Submental artery.
7. Mylohyoid nerve and vessels.
Contents of Posterior part of Triangle:
1. External carotid artery.
2. Carotid sheath and its contents.
3. Structures passing between the external and
internal carotid arteries
Clinical correlation :
Submandibular triangle is the common site of swellings due to:
(a) involvement of submandibular lymph nodes as they drain
lymph from widespread areas such as anterior two-third of
tongue (except tip), floor of mouth, frontal, ethmoidal, and
maxillary air sinuses, etc. and
(b) enlargement of the submandibular gland.
The efferents from submandibular lymph nodes mostly pass to
jugulo-omohyoid and partially to jugulodigastric nodes situated
along the internal jugular vein.
CAROTID TRIANGLE
BOUNDARIES:
Superiorly: Posterior belly of digastric supplemented by
stylohyoid.
Antero-inferiorly: Superior belly of omohyoid.
Posteriorly: Anterior border of sternocleidomastoid.
Roof: It is formed by investing layer of deep cervical
fascia. The superficial fascia over the roof contains
platysma, cervical branch of facial nerve and transverse
cervical nerve
Floor:
It is formed by four muscles:
1. Thyrohyoid.
2. Hyoglossus.
3. Middle constrictor.
4. Inferior constrictor.
CONTENTS OF CAROTID TRIANGLE:
• Arteries
• Veins
• Nerves
• Carotid sheath
• Lymph Nodes
• Apex of Parotid gland
Common Carotid Artery:
• It bifurcates in this triangle at the upper border of
Thyroid cartilage.
• It ascends from just behind the inferior angle of the
carotid triangle in the carotid sheath under cover of
anterior border of sternocleidomastoid and in front
of lower 4 cervical transverse processes
• Terminal branches ( ICA & ECA) lie deep to the
Posterior belly of Digastric and stylohyoid muscles.
Internal Carotid Artery:
The common carotid
artery and its
continuation, the
internal carotid artery
can be represented in
by a straight line from
sternoclavicular joint to
the retromandibular
fossa.
External Carotid Artery:
It ascends anteromedial to the internal
carotid artery and gives the five branches
in the triangle:
1. Ascending pharyngeal artery (first
branch).
2. Superior thyroid artery.
3. Lingual artery.
4. Facial artery.
5. Occipital artery.
Internal Jugular Vein:
• It descends posterolateral to
common and internal carotid
arteries and receives three
veins in the region of carotid
triangle:
1. Lingual vein.
2. Common facial vein.
3. Superior thyroid vein.
NERVES in CAROTID
TRIANGLE:
• Vagus Nerve
• Accessory nerve
• Hypoglossal Nerve
• Ansa Cervicalis
• Sympathetic chain
Vagus Nerve:
• Runs in Carotid sheath.
• 2 branches:
a) Pharnygeal branch
b) Superior Laryngeal nerve
(i) Internal LN – sensory
Supplies to Laryngeal mucosa, by passing through Thyrohyoid muscle
and Thyrohyoid membrane.
(ii) External LN – motor
Supplies to Cricothyroid muscles, Inferior constrictor muscles.
Accessory nerve:
• It crosses the carotid
triangle in Upper part
only and disappears
beneath the
sternocleidomastoid
muscle.
Hypoglossal Nerve:
• It runs forward superficially over External and
Internal carotid arteries in carotid triangle.
• It lies over the loop of lingual artery and enters
Hyoglossus muscle.
• It crosses the Internal Carotid Artery and gives off the
superior root of ansa cervicalis or descendens
hypoglossi. It lies in anterior wall of carotid sheath.
A
Ansa cervicalis:
• It is a U-shaped nerve
loop present in the region
of the carotid triangle
embedded in the anterior
wall of the carotid sheath.
• Supplies all infrahyoid
muscles except
thyrohyoid.
Branches:
i)Superior root (descendens hypoglossi)
formed by the descending branch of the
hypoglossal nerve (C1)
branches to – Superior belly of omohyoid.
ii)Inferior root (descendens cervicalis) – C2,C3.
Descends, and winds round the internal jugular vein
and continues antero-inferiorly and joins the superior
root in front of the common carotid artery at the
level of cricoid cartilage.
Carotid sheath:
• It is a facial sheath which encloses internal jugular vein,
and internal and common carotid arteries.
Formation :
• Anterior – Pretracheal fascia
• Posterior – Prevertebral fascia
Layers of
Deep
Cervical
Fascia :
Contents:
• Internal Carotid Arteries
• Internal Jugular Veins
• Vagus nerve
Relation:
• Anterior wall – Ansa
cervicalis
• Posterior wall –
Sympathetic chain
Carotid sinus:
• It is a fusiform dilatation at the terminal end of
common carotid artery or at the beginning of
internal carotid artery.
• It has rich innervation from glossopharyngeal, vagus,
and sympathetic nerves.
• Acts as a baroreceptor (pressure receptor) and
regulates the blood pressure in the cerebral arteries.
Carotid Body:
• It is a small oval structure situated behind the bifurcation of
the common carotid artery.
• Receives rich nerve supply from glossopharyngeal, vagus, and
sympathetic nerves.
• Acts as a chemoreceptor and responds to the changes in the
oxygen and carbon dioxide content of the blood.
• The excess of CO2 and reduced O2 tension in blood stimulates
it causing increase in blood pressure and heart rate.
A
CAROTID SINUS AND CAROTID BODY:
APPLIED ANATOMY:
CAROTID SINUS SYNDROME:
In some patients, there is a hypersensitivity of
carotid sinus.
• In such cases, rotation of head may leads to
sudden attack of syncope, due to slowing of
Heart rate.
MUSCULAR
TRIANGLE
Boundaries :
Anterior: Anterior median line of the neck, extending
from hyoid bone to the suprasternal notch.
Anterosuperior: Superior belly of the omohyoid.
Posteroinferior: Anterior border of
sternocleidomastoid.
Floor: It is formed by sternothyroid, sternohyoid, and
thyrohyoid muscles.
Roof :
It is formed by investing layer of deep cervical
fascia. The superficial fascia over the roof contains
anterior jugular vein and associated lymph nodes.
Contents :
Infrahyoid muscles, viz. sternothyroid, sternohyoid,
and thyrohyoid.
The important deeper structures in the region of
muscular triangle are thyroid gland, trachea, and
esophagus.
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