Anatomy of the Head and Neck

  • Course Information
  • Vasculature and Lymphatics
  • Innervation
  • Muscles
    • Muscles of the Neck
      30 min
  • Regions and Spaces of the Head
    • Infratemporal Fossa
      30 min
  • Nasal Cavity & Paranasal Air Sinuses
  • Oral Region
  • Pharynx and Esophagus
  • Layers, Regions and Triangles of the Neck
    • Muscles of the Neck
      30 min
  • Larynx, Trachea, and Thyroid Gland
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Muscles of the Neck

Muscles of the neck (Credit: Olek Remesz, CC BY-SA 4.0)

The neck is the meeting point and path of many muscles. Some of these muscles move the head as a unit (sternocleidomastoid), while others perform more specific movements such as lowering or raising the larynx (hyoid muscles).

We’ve got a lot to cover in the lesson, so you might want to freshen up before starting.

Right as we remove the skin, connective tissue, and fasciae from the cadaver, we’ll see the two most prominent muscles of the neck — the sternocleidomastoid, and the trapezius muscles. These muscles are commonly discussed during exams since they seem so straightforward that students tend to skip them altogether:

Sternocleidomastoid

SCM, in short, is enclosed within the investing layer of the deep fascia of the neck.

Movements

  1. Unilateral contraction (only one SCM is contracted) — Rotation and tilting the head to that side
  2. Bilateral contraction (both SCM are contracted) — Extension (“looking up”), flexion (“looking down”)

Origin and insertion

The origin of the SCM has two heads — one originates from the anterior surface of the manubrium, and the other from the superior medial third of the clavicle. They insert on the lateral surface of the mastoid process, and the lateral half of the superior nuchal line.

Innervation

SCM together with the trapezius, are the only muscles innervated by the spinal accessory nerve (CN XI).

SCM — Anatomography — CC BY-SA JP 2.1

Trapezius

Same as with the SCM, the trapezius is enclosed within the investing layer of the deep fascia of the neck. It can be split into three parts depending on the orientation of the muscle fibers (descending, transverse and ascending, on the image below they are shown as orange, red and purple).

Movements

  1. Elevation of the scapula (descending part)
  2. Retraction of the scapula (transverse part)
  3. Rotation of the scapula (ascending part)

Origin and insertion

The origin of the trapezius is the medial third of the superior nuchal line, external occipital protuberance, nuchal ligament, spinous process C7-T12, and lumbar and sacral spinous processes. It inserts onto the lateral third of the clavicle, acromion, and spine of the scapula.

Innervation

As mentioned before, it is innervated by the spinal accessory nerve (CN XI).

Trapezius divided into parts — Anatomography — CC BY-SA JP 2.1

 

Hyoid muscles

Suprahyoid Muscles

Muscles that attach to the hyoid bone and a structure above it. These muscles elevate the hyoid bone and the larynx, as well as form the floor of the mandible.

Stylohyoid

Origin: Styloid process
Insertion: Body of the hyoid bone
Innervation: Facial nerve (CN VII)

Mylohyoid

Forms the muscular oral diaphragm. This muscle joins from both sides of the neck to form a raphe — a tendentious line attaching both sides.

Origin: Mylohyoid line (mandible)
Insertion: Raphe and body of the hyoid bone
Innervation: Nerve to mylohyoid from the trigeminal nerve (CN V3)

Geniohyoid

Origin: Mental spine (mandible)
Insertion: Body of the hyoid bone
Innervation: Cervical plexus

Digastric

Has two bellies — an anterior, and a posterior. They both meet at the hyoid bone.

Origin: Anterior — Digastric fossa (mandible), posterior — mastoid bone
Insertion: Tendon on the body and greater horn of the hyoid bone
Innervation: Anterior — a branch of nerve to mylohyoid from CN V3, posterior — CN VII

Infrahyoid Muscles

Muscles that attach to the hyoid bone and a structure below it. These muscles depress the hyoid bone and the larynx.

Omohyoid

Has two bellies — a superior, and an inferior. They are divided by sling-like fascia.

Origin: Manubrium and medial clavicle
Insertion: Inferior surface of the hyoid bone

Sternohyoid

Origin: Manubrium
Insertion: Body of the hyoid bone

Sternothyoid

Origin: Manubrium
Insertion: Thyroid cartilage

Thyrohyoid

Origin: Thyroid cartilage
Insertion: Body and greater horn of hyoid bone

These muscles are innervated by ansa cervicalis (cervical plexus).

Scalene muscles

The scalene muscles (anterior, middle, and posterior) form a tent-like structure (scalenus tent — which covers the apex of the lung which protrudes about 1cm above the clavicle) at the anterolateral neck. In between the anterior and middle scalene, we can find the brachial plexus. The prevertebral fascia covers the scalenus muscles.

Anterior scalene

Origin: Transverse processes of C3–C6 vertebrae
Insertion: First rib

Middle scalene

Origin: Posterior tubercles of transverse processes of C5–C7 vertebrae
Insertion: First rib

Posterior scalene

Origin: Posterior tubercles of transverse processes of C5–C7 vertebrae
Insertion: Second rib

The scalene muscles are innervated by the cervical spinal nerves (anterior rami).

Deep muscles of the neck

The deep muscles of the neck — also known as the prevertebral muscles — are important in posture maintenance, stabilization, and flexion of the head.

  1. Levator scapulae
  2. Semispinalis capitis
  3. Splenius capitis
  4. Longus capitis
  5. Rectus capitis anterior
  6. Rectus capitis lateral

These muscles are innervated by the cervical plexus and cervical spinal nerves.

Suboccipital muscles

The suboccipital muscles are located underneath the semispinalis capitis muscle. These muscles are the deepest muscles of the neck region:

  1. Obliquus capitis superior
  2. Obliquus capitis inferior
  3. Rectus capitis posterior major
  4. Rectus capitis posterior minor

The first three form a pyramidal structure — the suboccipital triangle.

Obliquus capitis superior

Origin: Transverse process of C1
Insertion: Between superior and inferior nuchal lines

Obliquus capitis inferior

Origin: Posterior tubercle of the posterior arch of C2
Insertion: Transverse process of C1

Rectus capitis posterior major

Origin: Spinous process of C2
Insertion: Lateral part of the inferior nuchal line

Rectus capitis posterior minor

Origin: Posterior tubercle of the posterior arch of C1
Insertion: Medial part of the inferior nuchal line

The muscles of the suboccipital triangle are innervated by the suboccipital nerve (dorsal rami of C1).

Anterior view of the neck (Credit: OpenStax, CC BY-SA 4.0)

 

Lateral and posterior views of the neck (Credit: OpenStax, CC BY-SA 4.0)

References

1. Moore, Keith L., et al. Clinically Oriented Anatomy. Wolters Kluwer, 2018.
2. Standring, Susan, and Henry Gray. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. Elsevier, 2016.
3. Bertalan, Csillik, et al. Regional Anatomy. Medicina, 2008.

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