Samuele Hofner Von Balia

Lecture Guide: Anatomy of the Neck

Index

1 Overview 3

2 Skeletal Framework 3
2.1 Clinical Relevance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 Fascial Compartments 3

4 Triangles of the Neck 4

4.1 Clinical Relevance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

5 Neck Musculature 5

6 Blood Supply and Lymphatics 5

6.1 Carotid arteries: External (ECA) and Internal (ICA) . . . . . . . . . . . . . . . . . . . . . . 5
6.2 Thyrocervical Trunk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.3 Venous Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.4 Lymphatics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

7 Pharynx 8

8 Larynx 8

9 Test your Knowledge 9

9.1 Fascial Compartments Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.2 Triangles of the Neck Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.3 Musculature Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.4 Blood Supply Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

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9.5 Venous Drainage Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.6 Lymphatic System Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.7 Pharynx Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.8 Larynx Quiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

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1 Overview

The neck is a transitional anatomical region that connects the head to the trunk and supports vital func-
tions including respiration, speech, circulation, and swallowing. It extends anteriorly from the lower
border of the mandible to the upper surface of the manubrium and posteriorly from the superior nu-
chal line to the disc between C7 and T1.

Anatomical understanding is reinforced through imaging tools such as the Anatomage table and case-
based clinical integration (e.g. pointing structures in bold text).

2 Skeletal Framework

There are only few bones in the neck:

• Cervical vertebrae (C1-C7) form the axial skeleton of the neck. C1 (atlas) and C2 (axis) are spe-
cialized to allow _head rotation and _flexion-extension.

• Hyoid bone: A U-shaped bone without bony articulation, acting as an attachment for muscles of
the tongue, pharynx, and larynx. It is kept in place by ligamentous structures.

2.1 Clinical Relevance

Jefferson fractures involve the atlas and typically result from axial loads. Hyoid fractures may be observed
in forensic pathology as signs of strangulation.

3 Fascial Compartments

The fascial system of the neck is formed by two different fasciae:

• Superficial fascia: Contains platysma (cervical branch of CN VII 1 ). It begins in the superficial
fascia of the thorax and runs upwards attaching to the mandible, blending with the facial muscles.
The superficial fascia ends in the lateral portion of the neck, it does not continue posteriorly.

• Deep cervical fascia, including:

1. Investing layer: Completely surrounds the neck. It attaches posteriorly to the ligamentum
nuchae and to the spinous process of C7. It splits enclosing the trapezius and SCM. Anteriorly
it surrounds the infrahyoid muscles.

1 Facial nerve

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 2. Pre-vertebral layer: It surrounds the vertebral column and the muscles associated with it. It
splits in two layers creating a longitudinal space containing loose CT that extends from the
base of the skull through the thorax (crucial in case of infection).

3. Pre-tracheal layer: It surrounds trachea esophagus and thyroid. It begins superiorly at the
hyoid bone and reaches the upper thoracic cavity inferiorly. Posteriorly it is called buccopha-
ryngeal fascia, since it separates pharynx and esophagus from the prevertebral layer.

4. Carotid sheath: One pair of this sheath. It surrounds common carotid artery(not yet branched
into internal and external), internal jugular vein, and the vagus nerve.

Fascial planes dictate the spread of infections and are critical during neck dissections. The retropha-
ryngeal space provides a potential route for infections to reach the mediastinum.

4 Triangles of the Neck

Divided into anterior and posterior triangles:

• Anterior triangle, further divided into:

1. Submandibular/Digastric triangle, outlined by inferior border of the mandible superiorly and

the anterior/posterior bellies of the digastric muscle inferiorly

2. Submental triangle, outlined by hyoid bone inferiorly, anterior belly of digasstric muscle late-
rally and the midline

3. Muscular triangle, outlined by hyoid bone superiorly, superior belly of the omohyoid muscle,
and the anterior border of the SCM laterally, and the midline.

4. Carotid triangle, outlined by the superior belly of the omohyoid anteroinferiorly, stylohyoid
and posterior belly of the digastric superiorly, and the anterior border of SCM posteriorly. It
is possible to palpate the carotid artery here.

• Posterior triangle: Bounded by SCM, trapezius, and clavicle; further divided into:

1. Occipital triangle

2. Supraclavicular triangle

4.1 Clinical Relevance

Clinical application includes access to vascular structures (e.g. carotid endarterectomy) and lymph node
assessment for metastatic spread.

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5 Neck Musculature

Three different categories of muscles:

• Suprahyoid muscles: Stylohyoid, mylohyoid, digastric, geniohyoid. Function in swallowing and

floor-of-mouth support.

• Infrahyoid muscles: Omohyoid, sternohyoid, sternothyroid, thyrohyoid. Depress the hyoid and
larynx.

• Posterior triangle muscles: SCM, splenius capitis, levator scapulae, scalenes.

Ansa cervicalis (C1-C3) innervates most infrahyoid muscles. SCM involvement is key in torticollis.
Platysma function is relevant in facial expression and neck surgery.

6 Blood Supply and Lymphatics

6.1 Carotid arteries: External (ECA) and Internal (ICA)

At the beginning of the carotid system there are the right and left carotid arteries. The RIGHT common
carotid artery originates from the _brachiocephalic trunk immediately posterior to the right sternocla-
vicular joint. The LEFT common carotid artery is instead beginning in the thorax as a _DIRECT branch
of the aorta, entering the neck near the left sternoclavicular joint.

The common _carotid arteries branches into internal(lateral) and external(medial) carotid arteries
at the level of the superior edge of the thyroid cartilage.

IMPORTANT! Common and internal carotid arteries do NOT have any kind of branches.

The carotid artery presenting branches is the external one, forming:

• 3 anterior branches

1. Superior thyroid artery: It arises anteriorly and passes downward and forward to reach the
superior pole of the thyroid gland. THERE IS NO INFERIOR THYROID ARTERY.

2. Lingual artery: It arises at the level of the hyoid bone, passes deep to CNXII2 , and passes
inbetween the middle constrictor and hyoglossus muscles.

3. Facial artery: It passes deep to the stylohyoid and posterior belly of the digastric muscles,
continues deep between the submandibular gland and mandible, and emerges over the edge
of the mandible just anterior to the masseter muscle, to enter the face. Remember that facial
arteries are deeper than veins even if they usually run coupled.

• 3 posterior branches

2 Hypoglossal nerve

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 1. Ascending pharyngeal artery: It ascends between the internal carotid artery and the pharynx.

2. Occipital artery: It emerges at the level of the mastoid.

3. Posterior auricular artery

• 2 terminal branches

1. Superficial temporal artery

2. Maxillary artery: The largest of the terminal branches. It passes through the parotid gland
and continue in the infratemporal fossa, reaching the pterygopalatine fossa.

• Veins: IJV (deep), EJV (crosses SCM superficially), anterior jugular veins (variable). External ve-
nous drainage pathways are important during neck surgery to prevent hemorrhage.

6.2 Thyrocervical Trunk

The thyrocervical trunk has 4 branches:

• Suprascapular artery

• Transverse cervical artery

• Ascending cervical artery

• Inferior thyroid artery

All 4 parathyroid glands are fed by the inferior thyroid artery

6.3 Venous Drainage

The venous drainage is right deep the platysma. A common question that could be present in the exam
could be Ïs the internal jugular vein superficial or deeper to the omohyoid muscle?”The answer is that
the internal jugular is always deep to the omohyoid. This is to highlight the importance of understanding
layering and connections of structures to other reference systems.

Starting with the internal jugular vein, there are two specular one to the other. It begins as a continua-
tion of the sigmoid sinus (a dural venous sinus) forming a sort of bulging known as the superior bulb
of the IJV; it receives another dural sinus: the inferior petrosal sinus. The aforementioned structures are
small vessels located at the base of the skull, hence very important given the fact that could be easily
damaged. The IJV exits the skull at the level of the jugular foramen as it enters the carotid sheath and it
establishes an association with 3 nerves:

1. Glossopharyngeal (CN IX)

2. Vagus (CN X)

3. Accessory (CN XI)

While the IJV shares the jugular foramen with CNs IX, X, and XI, the carotid artery has its own foramen.

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 The internal jugular vein exits the jugular foramen at the base of the skull and proceeds through the
length of the neck initially remaining posterior to the carotid artery and later translating into a more
lateral position. The vagus nerve remains partially in-between the two vessels.

The paired internal jugular veins join with the subclavian veins posterior to the sternal end of the
clavicle to form the right and left brachiocefalic veins. Remember that it does not exist such thing as the
brachiocephalic artery.

Tributaries of each internal jugular vein include:

1. Inferior petrosal sinus

2. Pharyngeal vein

3. Facial vein

4. Lingual vein

5. Occipital vein

6. Superior thyroid vein

7. Middle thyroid vein (it does not have a complementary artery), usually it is the first vein tro be
ligated during surgery of the neck district due to the fact that is the only lateral connection of the
thyroid gland to the IJV.

Proceding with the external jugular veins, they are lying over the SCM muscle and ascend posterior-
ly to the angle of the mandible where they branch into the posterior auricular vein (at the level of the
mastoid tip) and the retromandibular vein. From the retromandibular vein two other branches are found
more cranially, which are the superficial temporal vein and the maxillary veins, that join in the substance
of the parotid gland and start descending at the angle of the mandible. At this point there are an anterior
and posterior division. The first one is joining the facial vein to form the common facial vein (then beco-
ming a tributary of the IJV); the posterior division joins instead the posterior auricular vein forming the
external jugular vein.

The common facial vein is particularly important because it connects the superficial and deep vascula-
ture (joining the IJV) and due to this compensational network is possible to live even with only one IJV.

Lastly the anterior jugular veins, although variable and inconsistent, are usually described as drai-
ning the anterior aspect of the neck. These paired venous channels come together at or just superior to
the hyoid bone. Once formed, each anterior jugular vein descends on either side of the midline of the
neck. Inferiorly, near the medial attachment of the sternocleidomastoid muscle, each anterior jugular
vein pierces the investing layer of cervical fascia to enter the subclavian vein. Often, the right and left
anterior jugular vein communicate with each other, being connected by a jugular venous arch, in the area
of the suprasternal notch; however, this is not always prevent and anatomical variance is found among
different people. Occasionally, the anterior jugular vein may enter the external jugular vein immediately
before the external jugular vein enters the subclavian vein.

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6.4 Lymphatics

The components of the lymphatic system of the head and neck district include:

• Superficial cervical nodes: Located along the external jugular vein over the SCM; include submen-
tal, submandibular, parotid, mastoid, and occipital nodes. These drain the scalp, face, oral cavity,
and superficial neck.

• Deep cervical nodes: Lie along the internal jugular vein, deep to SCM. They are divided into:

1. Upper deep cervical nodes: Include the jugulodigastric node, which drains the tonsils and
pharynx.

2. Lower deep cervical nodes: Include the jugulo-omohyoid node, draining the tongue and lower
oral cavity.

Lymphatics from right and left jugular and subclavian trunks drain some of the lymph arriving from
the deep cervical nodes into the right lymphatic duct (on the right) or into the thoracic duct (left side).

To precisely localize the position of tumors in the neck the Robbins classification is what is used by
clinicians in oncologic surgery. Levels span from I to VI:

1. Level I: Submental(IA) and submandibular(IB)

2. Level II: Upper jugular

• IIA anterior (medial) to the spinal accessory nerve

• IIB posterior (lateral) to the spinal accessory nerve

3. Level III: Mid-jugular

4. Level IV: Lower jugular

5. Level V: Posterior triangle

• VA: from inferior border of cricoid cartilage above

• VB: from cricoid cartilage to the clavicle

6. Level VI: Prelaryngeal, pretracheal, and paratracheal

7 Pharynx

8 Larynx

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9 Test your Knowledge

9.1 Fascial Compartments Quiz

Case: A patient with a dental abscess presents with chest pain and fever. Imaging shows a descending
infection into the mediastinum. Through which space did the infection most likely spread?

A) Carotid sheath B) Retropharyngeal space C) Pretracheal space D) Investing fascia

Correct Answer: B

Explanation: The retropharyngeal space extends from the base of the skull into the posterior media-
stinum, making it a common route for deep neck infections to spread into the thorax. The other fascial
planes are more compartmentalized.

9.2 Triangles of the Neck Quiz

Case: A surgeon plans an endarterectomy (a surgical procedure to remove plaque buildup from inside
an artery) of a large vessel. Which triangle will they operate in?

A) Submental B) Muscular C) Carotid D) Occipital

Correct Answer: C

Explanation: The carotid triangle contains the common carotid artery bifurcation, making it the surgi-
cal target for vascular interventions. The submental and muscular triangles do not contain major vessels.

9.3 Musculature Quiz

Case: A newborn has a tilted head with the chin pointing opposite to the affected side. What muscle is
most likely involved?

A) Platysma B) Mylohyoid C) Sternocleidomastoid D) Digastric

Correct Answer: C

Explanation: Congenital torticollis is due to unilateral shortening of the SCM, leading to head tilt
toward and chin rotation away from the affected side.

9.4 Blood Supply Quiz

Case: A patient has massive oropharyngeal bleeding. Which arterial branch is most likely responsible?

A) Superior thyroid artery B) Maxillary artery C) Posterior auricular artery D) Occipital artery

Correct Answer: B

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 Explanation: The maxillary artery is a major blood supplier to deep facial structures and the oropha-
rynx. Hemorrhages in this region often involve this artery.

9.5 Venous Drainage Quiz

Case: A neck surgery often risks damaging a vein that lies deep to the SCM and drains the brain. Which
is it?

A) External jugular vein B) Facial vein C) Internal jugular vein D) Retromandibular vein

Correct Answer: C

Explanation: The IJV is deep to the SCM and is the primary venous drainage route from the brain. The
EJV and facial veins are more superficial.

9.6 Lymphatic System Quiz

Case: A patient with a mass in the submental triangle is biopsied and reveals squamous cell carcinoma.
Which Robbins sublevel is involved?

A) Level IB B) Level IIA C) Level IA D) Level VI

Correct Answer: C

Explanation: The submental triangle corresponds to Level IA in the Robbins classification, associated
with drainage from the lower lip and chin.

9.7 Pharynx Quiz

9.8 Larynx Quiz

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