MUSCLE ANATOMY – THE NECK
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STERNOCLEIDOMASTOID
– Radiopaedia .
– It has two heads that meld to form one insertion. Sternocleidomastoid muscle, along with the trapezius muscle, is invested by the superficial layer of the deep cervical fascia, which splits around it. Sternocleidomastoid muscle divides the neck into anatomical anterior and posterior triangles.
- origin: manubrium, medial clavicle
- insertion: mastoid process, superior nuchal line
- innervation: accessory nerve (CN XI)
- action: lateral flexion, flexion and rotation of the head on the neck
SCALENES – ANTERIOR-MEDIUS-POSTERIOR
– Radiopaedia – The scalene muscles are a group of three closely related neck muscles.
- Origin: C2 – C7
- Insertion:
Anterior: inner border of first rib (scalene tubercle)
Medius or Middle: upper surface of first rib
Posterior: outer surface of second rib - Innervation: C3 – C8
- Action:
Anterior: (1) raises first rib -inspiration (2) adjunct: neck rotation/flexion
Medius or Middle: (1) raises first rib – respiratory inspiration (2) acting bilaterally: neck flexion (3) acting unilaterally: lateral neck flexion and rotation
Posterior: (1) raises second rib – respiratory inspiration (2) acting together: neck flexion (3) acting on one side: lateral neck flexion and rotation
LEVATOR SCAPULAE
– Radiopaedia .
– A muscle of the upper limb that connects the pectoral girdle to the cervical spine.
– A muscle of the upper limb that connects the pectoral girdle to the cervical spine.
- Origin: C1-C4 transverse processes
- Insertion: superior angle of the scapula
- Innervation: direct branches from the C3-4 spinal nerves, and the dorsal scapular nerve (C5)
- Action: (1) elevates medial border of the scapula (2) when scapula is fixed, lateral flexion of the neck
SPLENIUS CAPITIS
– Radiopaedia .
– A strap-like muscles that, along with the splenius cervicis, comprise the superficial layer of intrinsic back muscles.
– A strap-like muscles that, along with the splenius cervicis, comprise the superficial layer of intrinsic back muscles.
- Origin: ligamentum nuchae, and the tips of the spinous processes and associated supraspinous ligaments of C7 and the upper three to four thoracic vertebrae
- insertion: mastoid process and rough surface of the occipital bone below the lateral third of the superior nuchal line
- Relations: deep to the trapezius; superficial to the semispinalis capitis and the longissimus capitis; forms the floor of the posterior neck triangle, lying between the sternocleidomastoid and the trapezius
- Innervation: lateral branches of the 2nd and 3rd cervical dorsal rami from the cervical plexus
- Action:
(1) Rotates the head to the same side: when acting unilaterally and synergistically with the sternocleidomastoid
(2) Extends the head: when acting bilaterally
VIDEOS
- Noted Anatomist – Triangles of the Neck .
(1) Anterior Triangle (2) Posterior Triangle - Noted Anatomist – Muscles & Nerves of the Neck .
- Webster – Posterior Neck Muscles .
- Webster – Lateral Neck Muscles .