Functional Anatomy 1 - Lecture 3: Muscles of the Back and Neck

superficial back muscles

• extrinsic

• connect upper limb to trunk

• attach to the clavicle/humerus/scapula

• innervated by names peripheral nerves/ventral rami

intermediate back muscles

• extrinsic

• serratus posterior superior

• serratus posterior inferior

• innervated by intercostal nerves

deep back muscles

• intrinsic

• function

  • move vertebral column

  • posture

  • shock absorbers

• all innervated by the posterior/dorsal rami of the segments they span

• 4 groups (superficial to deep)

  • splenius muscles (capitis, cervicis) (S)

  • erector spinae (I)

  • transversospinales (D)

  • segmental (D)

splenius capitis

O: ligamentum nuchae and spinous process of C7-T4

I: lateral 1/3 of superior nuchal line and mastoid process

splenius cervicis

O: spinous processes of T3-T6

I: transverse process of C1-C3

splenius muscles actions

unilaterally: ipsilateral lateral flexion and rotation of head (capitis) and neck (cervicis)

bilaterally: extend head (capitis) and neck (cervicis)

erector spinae

lateral to medial

• iliocostalis

• longissimus

• spinalis

intermediate layer!

iliocostalis

O: iliac crest/lumbar fascia, posterior sacrum

I: angles of ribs (lumbar and thoracic), transverse processes C4-6 (cervical)

longissimus

O: iliac crest, lumbar fascia, lumbar TPs (thoracis), TPs upper thoracic (cervicis/capitis)

I: thoracic TPs/ribs (thoracis), cervical TPs (cervicis), mastoid (capitis)

spinalis

O: spinous process upper lumbar and thoracic

I: spinous processes upper thoracic and cervical

erector spinae group action

bilaterally: extend head and vertebral column

unilaterally: ipsilateral lateral flexion of vertebral column

• more lateral attachment, more oblique fiber direction, more contribution to SB

transversospinales

deep layer, note the superior and medial fiber direction for all three

semispinalis

• most superficial of deep layer

• prominent in cervical region

• fibers span 4-6 levels

O: TP C4-T10

I: SPs upper thoracic/cervical and superior nuchal line

multifidus

• prominent in lumbar region

O: posterior sacrum/pelvis, lumbar superior articular processes, TP thoracic

I: SP 2-4 levels above

rotatores

• deepest of deep layer

• prominent in thoracic region

O: transverse processes

I: lamina and SP 1-2 above

transversopinales group action

• bilaterally: extend vertebral column

• unilaterally: contralateral rotation

  • pull the spinous process of adjacent/superior vertebrae towards the transverse process of their origin

segmental (deepest) muscles

• interspinous and intertransversus

  • run between spinous processes or transverse processes

  • provide stability

    • minimal movement

rectus capitis posterior major

O: SP of C2

I: lateral inferior nuchal line

A: extend head; ipsilateral rotation of head

N: posterior ramus of C1 (suboccipital nerve)

rectus capitis posterior minor

O: posterior tubercle of C1

I: medial aspect of inferior nuchal line

A: extend head

• not part of sub-occipital triangle

N: posterior ramus of C1 (suboccipital nerve)

obliquus capitis inferior

O: SP of C2

I: TP of C1

• no attachment to skull

A: ipsilateral rotation of C1 on C2

N: posterior ramus of C1

obliquus capitis superior

O: TP of C1

I: occiput between superior and inferior nuchal lines

A: extend head, ipsilateral lateral flexion

N: posterior ramus of C1 (suboccipital nerve)

suboccipital nerve (C1)

• emerges in middle of triangle

• motor innervation to all 3 muscles of the suboccipital triangle

greater occipital nerve (C2)

• emerges inferior to triangle

• passes through superficial muscles

• innervates skin on posterior scalp

• cervicogenic headaches

cutaneous innervation of C1-C3

platysma

• very superficial

• thin and small muscle fibers

• O: fascia in the anterior neck and mandible

• I: fascia covering pectoralis major

• A: muscle of facial expression

• N: facial nerve 7

posterior triangle

• anterior: SCM

• inferior: clavicle

• posterior: upper trapezius

anterior triangle

• anterior: midline

• superior: mandible

• posterior: SCM

sternocleidomastoid

O: mastoid process/lateral superior nuchal line

I: manubrium of sternum and medial clavicle

A: ipsilateral lateral flexion, contralateral rotation

N: spinal accessory nerve

posterior triangle

• floor

  • splenius capitis

  • levator scapulae

  • posterior scalene

  • anterior scalene

  • middle scalene

• structures within

  • external jugular vein

  • subclavian artery and vein

  • roots of brachial plexus

  • suprascapular nerve

  • omohyoid muscle

  • cervical plexus

    • anterior rami C1-C4

anterior scalene

O: transverse process of C3-C6

I: 1st rib

A:

• bilaterally: cervical flexion

• unilaterally: laterally flex the cervical spine

• alternate: accessory respiratory muscle by raising 1st rib

N: C4-C6 ventral rami

• anterior to phrenic nerve, posterior to subclavian artery

middle scalene

O: TP of C4-C7

I: superior surface of 1st rib

A: ipsilateral lateral flexion cervical spine, elevate ribs

N: mid-lower cervical ventral rami

posterior scalene

O: TP C4-C6

I: lateral superior surface of 2nd rib

A: ipsilateral lateral flexion cervical spine, elevate ribs

N: mid-lower cervical ventral rami

suprahyoid muscles

floor of mouth, stable base for tongue

• digastric muscle

• stylohyoid

• mylohyoid

• geniohyoid

infrahyoid muscles

more hyoid during speech and swallowing actions

• omohyoid

• thyrohyoid

• sternothyroid

hyoid muscles

• supra vs infra

• defined by their position relative to the hyoid bone

• as a whole, aid in movements of swallowing and fine movements of eating

• suprahyoids innervated by cranial nerves

• infrahyoids innervated by branches off the ansa cervicalis

suprahyoids

• floor of the mouth

• provide stable base for tongue movements

• elevate hyoid to assist in speech and swallow

• include

  • digastric muscle, stylohyoid, mylohyoid, geniohyoid

digastric muscle

• 2 muscle bellies

O: mastoid process

• intermediate tendon attached to hyoid

I: anterior mandible

A:

• hyoid fixed: depress and retract mandible

• mandible is fixed: elevate hyoid

N:

• posterior belly: facial nerve

• anterior belly: trigeminal nerve, mandibular division

stylohyoid

O: styloid process of skull

I: hyoid

A: elevates hyoid

N: facial nerve

mylohyoid

O: mandible

I: hyoid

• forms the floor of the mouth

A:

• hyoid fixed: depress mandible

• mandible fixed: elevate hyoid

N: trigeminal nerve, mandibular division

geniohyoid

• deep to mylohyoid

O: mandible

I: hyoid

A:

• hyoid fixed: depress mandible

• mandible fixed: elevate hyoid

N: C1 via hypoglossal nerve (CN 12)

infrahyoids

• “strap muscles” because of appearance

  • omohyoid, thyrohyoid, sternothyroid

A: stabilize the hyoid with the suprahyoid muscles, depress hyoid to assist with speech and swallow

N: ansa cervicalis

• except thyrohyoid innervated by C1 via hypoglossal (CN12)

omohyoid

O: hyoid

I: superior border of scapula (near notch)

• superior and inferior bellies

  • superficial to internal jugular vein

thryohyoid

O: hyoid

I: thyroid cartilage

A: stabilizes/depresses hyoid

• if hyoid is fixed it will elevate the larynx

sternothyroid

O: thyroid cartilage

I: manubrium of sternum

• not attached to hyoid bone

A: depress larynx

deep anterior muscles

• longus colli

• oblique portion

  • O: bodies/transverse process of C3-5

  • I: C5, C6 vertebrae

• linear portion

  • O: bodies of C5-T3

  • I: bodies of C2-C4 (linear)

• A:

  • bilaterally: flexes cervical spine

  • unilaterally: ipsilateral lateral flexion cervical spine

• N: C2-C6 ventral rami

longus capitis

O: TP C3-C6

I: basilar occipital bone

A: flexion and ipsilateral lateral flexion of head

N: C1-C3 ventral rami

veins of the neck

• retromandibular

• anterior jugular

• posterior auricular

• external jugular

• transverse cervical

• internal jugular

arteries of the neck

• superior thyroid

• superior laryngeal

• common carotid

• inferior laryngeal

• inferior thyroid

• left recurrent laryngeal

• left subclavian