Posterior and Anterior Triangles of Neck

Origin and Insertion

Sternocleidomastoid

O: Llateral surface of mastoid process of temporal bone and lateral half of superior nuchal line

I:

Sternal head: anterior surface of manubrium of sternum

Clavicular head: superior medial clavicle

Origin and Insertion

Trapezius

O: medial third of superior nuchal line; external occiptal protuberance; nuchal ligament; spinous processes of C7-T12

I: lateral third of clavicle, acromion, and spine of scapula

Origin and Insertion

Levator Scapulae

O: posterior tubercles of transverse processes of C1-C4

I: medial border of scapula superior to root of scapular spine

Origin and Insertion

Scalenus Anterior

O: transverse processes of C3-C6

I: 1st rib

Origin and Insertion

Scalenus Medius

O: posterior tubercles of transverse processes of C5-C7

I: superior surface of 1st rib; posterior to groove for subclavian artery

Origin and Insertion

Scalenus Posterior

O: posterior tubercles of transverse processes of C5-C7

I: external border of 2nd rib

Suprahyoid Group

digastric (anterior/posterior belly and intermediate tendon), geniohyoid, mylohyoid, stylohyoid

Infrahyoid Group

omohyoid (superior and inferior belly), sternohyoid, thyrohyoid, sternothyroid

Innervation

Sternocleidomastoid

spinal accessory (CN XI; motor), C3-C4 nerves (pain and proprioception)

Innervation

Trapezius

spinal accessory (CN XI; motor), C3-C4 nerves (pain and proprioception)

Innervation

Levator Scapulae

Peripheral: dorsal scapular

Innervation

Scalenus Anterior

C4-C6 VPR

Innervation

Scalenus medius

cervical VPR

Innervation

Scalenus Posterior

C7-C8 VPR

Innervation

Digastric

nerve to mylohyoid, a branch of inferior alveolar nerve

digastric (preparotid) branch of facial nerve (CN VII)

Innervation

Stylohyoid

stylohyoid (preparotid) branch of facial nerve (CN VII)

Innervation

Mylohyoid

nerve to mylohyoid, a branch of inferior alveolar nerve from mandibular nerve CN V3)

Innervation

Geniohyoid

C1 via hypoglossal nerve (CN XII) and nerve to geniohyoid

Innervation

Sternohyoid

C1-C3 by a branch of ansa cervicalis

Innervation

Omohyoid

C1-C3 by a branch of ansa cervicalis

Innervation

Sternothyroid

C2-C3 by a branch of ansa cervicalis

Innervation

Thyrohyoid

C1 via hypoglossal nerve (CN XII) and nerve to thyrohyoid

Action

Sternocleidomastoid

Unilateral Contraction: ipsilateral side bend, contralateral rotation of cervical spine

Bilateral Contraction:

(1) extends head at atlanto-occipital joints

(2) lower cervical flexion

(3) extends superior cervical vertebrae while flexing inferior vertebrae so chin is thrust forward with head kept level

Action

Trapezius

Upper: scapular elevation

Lower: scapular depression

Middle: scapular retraction

Upper and Lower Together: part of force couple that upwardly rotates scapula

Action

Levator Scapulae

scapular elevation and downward rotation

Action

Scaleneus Anterior

cervical flexion; elevates 1st rib during forced inspiration

Action

Scalenus Medius

cervical lateral flexion; elevates 1st rib during forced inspiration

Action

Scalenus Posterior

cervical lateral flexion; elevates 2nd rib during forced inspiration

Action

Digastric

fixate and elevate hyoid

Action

Stylohyoid

fixate and elevate hyoid

Action

Mylohyoid

fixate and elevate hyoid

Action

Geniohyoid

fixate and elevate hyoid

Action

Sternohyoid

fixate/depress hyoid and thyroid cartilage

Action

Omohyoid

fixate/depress hyoid and thyroid cartilage

Action

Sternothyroid

fixate/depress hyoid and thyroid cartilage

Action

Thyrohyoid

fixate/depress hyoid and thyroid cartilage