Occasionally, a small thyroid ima artery arises from the brachiocephalic trunk or the arch of the aorta and ascends on the anterior surface of the trachea to supply the thyroid gland.
The neck is a tube providing continuity
from the head to the trunk.
It extends anteriorly from the lower
border of the mandible to the upper
surface of the manubrium of sternum.
Posteriorly from the superior nuchal line
on the occipital bone of the skull to the
intervertebral disc between the CVII and
• Within the tube four compartments provide
the visceral compartment is anterior and
contains parts of the digestive and respiratory
systems, and several endocrine glands;
the vertebral compartment is posterior and
contains the cervical vertebrae, spinal cord,
cervical nerves, and muscles associated with the
the two vascular compartments are lateral and
contain the major blood vessels and the vagus
• For descriptive purposes the neck is divided
into anterior and posterior triangles.
• Anterior triangle; its boundaries are the
anterior border of the sternocleidomastoid
muscle, the inferior border of the mandible,
and the midline of the neck;
• Posterior triangle; its boundaries are the
posterior border of the sternocleidomastoid
muscle, the anterior border of the trapezius
muscle, and the middle one-third of the
ANTERIOR TRIANGLE OF THE NECK
• The anterior triangle of the neck is outlined by
the anterior border of the
sternocleidomastoid muscle laterally, the
inferior border of the mandible superiorly, and
the midline of the neck medially.
It is further subdivided into several smaller
triangles as follows:
the submandibular triangle is outlined by the
inferior border of the mandible superiorly and
the anterior and posterior bellies of the
digastric muscle inferiorly;
• the submental triangle; outlined by the hyoid
bone inferiorly, the anterior belly of the digastric
muscle laterally, and the midline;
• the muscular triangle is outlined by the hyoid
bone superiorly, the superior belly of the
omohyoid muscle, and the anterior border of the
sternocleidomastoid muscle laterally, and the
• the carotid triangle is outlined by the superior
belly of the omohyoid muscle anteroinferiorly,
the stylohyoid muscle and posterior belly of the
digastric superiorly, and the anterior border of
the sternocleidomastoid muscle posteriorly.
• Each of these triangles contains numerous
structures that can be identified as being
within a specific triangle, passing into a
specific triangle from outside the area,
originating in one triangle and passing to
another triangle, or passing through several
triangles while passing through the region.
Muscles in anterior triangle
• The muscles in the anterior triangle of the
neck can be grouped according to their
location relative to the hyoid bone:
muscles superior to the hyoid are classified as
suprahyoid muscles and include the
stylohyoid, digastric, mylohyoid, and
muscles inferior to the hyoid are infrahyoid
muscles and include the omohyoid,
sternohyoid, thyrohyoid, and sternothyroid.
The four suprahyoid muscles are in the
submental and submandibular triangles.
They pass in a superior direction from the
hyoid bone to the skull or mandible and raise
the hyoid, as occurs during swallowing.
1. Stylohyoid; innervated by the facial nerve
[VII], it pulls the hyoid bone
posterosuperiorly during swallowing.
2. Digastric; has 2 bellies (anterior and
posterior) connected by a tendon which
attaches to the body of the hyoid bone.
Innervation of the digastric muscle is from
two different cranial nerves.
• Posterior belly is by facial nerve (CN VII)
• Anterior belly is by trigeminal nerve (CN V)
3. Mylohyoid; It is innervated by the trigeminal
nerve [CN V]. It supports and elevates the floor of
the mouth and elevates the hyoid bone.
4. Geniohyoid; is innervated by a branch from the
anterior ramus of C1 carried along the hypoglossal
• It has two functions depending on which bone is
fixation of the mandible elevates and pulls the
hyoid bone forward;
fixation of the hyoid bone pulls the mandible
downward and inward.
• Infrahyoid muscles;
The four infrahyoid muscles are in the
They attach the hyoid bone to inferior
structures and depress the hyoid bone.
They also provide a stable point of attachment
for the suprahyoid muscles.
Because of their appearance, they are
sometimes referred to as the 'strap muscles'.
Sternohyoid; is innervated by the anterior
rami of C1 to C3 through the ansa cervicalis.
It depresses the hyoid bone
Omohyoid; Lateral to the sternohyoid muscle,
This muscle consists of two bellies with an
intermediate tendon in both the posterior and
anterior triangles of the neck.
It is innervated by the anterior rami of C1 to
C3 through the ansa cervicalis.
The omohyoid depresses and fixes the hyoid
Thyrohyoid; is located deep to the superior
parts of the omohyoid muscle. It is innervated
by fibers from the anterior ramus of C1 that
travel with the hypoglossal nerve [XII].
Sternothyroid; the last of the infrahyoid group
of muscles. is innervated by the anterior rami
of C1 to C3 through the ansa cervicalis.
The sternohyoid muscle draws the larynx
(thyroid cartilage) downward
Vessels in the anterior triangle
Passing through the anterior triangle of the
neck are the common carotid arteries and
their branches, the external and internal
These vessels supply all structures of the head
• The common carotid arteries are the beginning
of the carotid system.
• the right common carotid artery originates from
the brachiocephalic trunk;
• the left common carotid artery begins in the
thorax as a direct branch of the arch of the aorta.
• They both ascend through the neck, lateral to the
tracheal and oesophagus not giving any branch in
• Near the superior edge of the thyroid cartilage
each common carotid artery divides into its two
terminal branches-the external and internal
Origin of the common carotid arteries
• The superior part of each common carotid
artery and its division into external and
internal carotid arteries occurs in the carotid
• At the bifurcation, the common carotid artery
and the beginning of the internal carotid
artery are dilated.
• This dilation is the carotid sinus and contains
receptors that monitor changes in blood
pressure and are innervated by a branch of
the glossopharyngeal nerve [IX].
• Another accumulation of receptors in the area
of the bifurcation is responsible for detecting
changes in blood chemistry, primarily oxygen
• This is the carotid body and is innervated by
branches from both the glossopharyngeal [IX]
and vagus [X] nerves.
Internal carotid arteries
• After its origin, the internal carotid artery
ascends toward the base of the skull.
• It gives off no branches in the neck and enters
the cranial cavity through the carotid canal in
the petrous part of the temporal bone.
• The internal carotid arteries supply the
cerebral hemispheres, the eyes and the
contents of the orbits, and the forehead.
External carotid arteries & its branches
Superior thyroid artery
Thyrohyoid muscle, internal structures of
the larynx, sternocleidomastoid and
cricothyroid muscles, thyroid gland
Ascending pharyngeal artery
Pharyngeal constrictors and
stylopharyngeus muscle, palate, tonsil,
pharyngotympanic tube, meninges in
posterior cranial fossa
Muscles of the tongue, palatine tonsil,
soft palate, epiglottis, floor of mouth,
All structures in the face from the inferior
border of the mandible anterior to the
masseter muscle to the medial corner of
the eye, the soft palate, palatine tonsil,
pharyngotympanic tube, submandibular
External carotid arteries & its branches
Sternocleidomastoid muscle, meninges in
posterior cranial fossa, mastoid cells,
deep muscles of the back, posterior scalp
Posterior auricular artery
Parotid gland and nearby muscles,
external ear and scalp posterior to ear,
middle and inner ear structures
Superficial temporal artery
Parotid gland and duct, masseter muscle,
lateral face, anterior part of external ear,
temporalis muscle, parietal and temporal
External acoustic meatus, lateral and
medial surface of tympanic membrane,
temporomandibular joint, dura mater on
lateral wall of skull and inner table of
cranial bones, trigeminal ganglion and
dura in vicinity, mylohyoid muscle,
mandibular teeth, skin on chin, temporalis
muscle, outer table of bones of skull in 31
• Collecting blood from the skull, brain, superficial
face, and parts of the neck, the internal jugular
vein begins as a dilated continuation of the
sigmoid sinus, which is a dural venous sinus.
• The paired internal jugular veins join with the
subclavian veins posterior to the sternal end of
the clavicle to form the right and left
• Tributaries to each internal jugular vein include
the inferior petrosal sinus, and the facial, lingual,
pharyngeal, occipital, superior thyroid, and
middle thyroid veins.
• Numerous cranial and peripheral nerves:
pass through the anterior triangle of the neck
as they continue to their final destination;
send branches to structures in or forming
boundaries of the anterior triangle of the
while in the anterior triangle of the neck, send
branches to nearby structures.
The cranial nerves in these categories include:
the facial [VII], glossopharyngeal [IX], vagus
[X], accessory [XI], and hypoglossal [XII].
The peripheral nerves in these categories
include the transverse cervical nerve from the
cervical plexus and the upper and lower roots
of the ansa cervicalis.
Cranial nerves & its branches
Facial nerve [VII]
the posterior belly of the digastric;
Glossopharyngeal nerve [IX]
stylopharyngeus muscle, sends a branch
to the carotid sinus, and supplies sensory
branches to the pharynx.
Vagus nerve [X]
Gives a motor branch to the pharynx, a
branch to the carotid body, the superior
laryngeal nerve (which divides into
external and internal laryngeal branches),
and possibly a cardiac branch.
Accessory nerve [XI]
No branches in the anterior triangle but
innervates the trapezius
Hypoglossal nerve [XII]
No branches in the anterior triangle but
innervates the tongue
Peripheral nerves & its branches
Transverse cervical nerve
provides cutaneous innervation to this
innervates the inferior belly of the
omohyoid, and the lower parts of the
sternohyoid and sternothyroid muscles.
• They are both endocrine glands positioned
anteriorly in the neck.
• Both glands begin as pharyngeal outgrowths
that migrate caudally to their final position as
• The thyroid gland is a large, unpaired gland,
while the parathyroid glands, usually four in
number, are small and are on the posterior
surface of the thyroid gland.
• The thyroid gland is anterior in the neck below
and lateral to the thyroid cartilage.
• It consists of two lateral lobes (which cover
the anterolateral surfaces of the trachea, the
cricoid cartilage, and the lower part of the
• It also has the isthmus that connects the
lateral lobes and crosses the anterior surfaces
of the second and third tracheal cartilages.
• It lies deep to the sternohyoid, sternothyroid,
and omohyoid muscles.
• It is in the visceral compartment of the neck.
• This compartment also includes the pharynx,
trachea, and esophagus and is surrounded by
the pretracheal layers of fascia.
• Two major arteries supplies the thyroid gland;
• The superior thyroid artery and the inferior
The superior thyroid artery is the first branch of
the external carotid artery, it descend along the
lateral margin of thyrohyoid muscle and divides
into an anterior and a posterior glandular
branch at the superior pole of the gland.
Anterior glandular-supplies superior pole and
anastomose with the opposite anterior glandular.
Posterior glandular- passes posterior, may
anastomose with inferior thyroid artery
Inferior thyroid artery
The inferior thyroid artery is a branch of the
thyrocervical trunk, which arises from the first
part of the subclavian artery.
At the thyroid gland the inferior thyroid artery
divides into an:
inferior branch, which supplies the lower part of
the thyroid gland and anastomoses with the
posterior branch of the superior thyroid artery;
an ascending branch, which supplies the
• The thyroid gland is closely related to and
supplied by the recurrent laryngeal nerves.
• After branching from the vagus nerve [X] and
looping around the subclavian artery on the
right and the arch of the aorta on the left, the
recurrent laryngeal nerves ascend in a groove
between the trachea and esophagus.