Cx muscles

Question 1

Describe the 4 groups of muscles in the Cx region, and the muscles they include.

Answer 1

Superficial Lateral, Lateral, Anterior Neck & Suboccipitals.

Superficial Lateral:

• SCM
• Traps
• Platysma

Lateral:

• Levator scapulae
• Scalenes (posterior & middle)
• Splenius capitis
• Rectus capitis lateralis

Anterior neck:

• suprahyoids
• infrahyoids
• longus colli
• longus capitis
• rectus capitis anterior

Suboccipitals

• rectus capitis posterior major
• rectus capitis posterior minor
• obliquus capitis superior
• obliquus capitis inferior

Question 2

Describe the anatomy of the superficial lateral neck muscles

Answer 2

SCM:
Has two heads (sternal and clavicular)
PA: mastoid process of temporal bone
DA: sternal head: manubrium; clavicular head: medial 1/3 clavicle
NS: CN XI accessory
Actions: 
unilateral: contralateral rotation
bilateral: protraction of the head

Trapezius:
Has three aspects (upper, middle and lower)
PA: middle 1/3 superior nuchal line, nuchal ligament, EOP, SPs C7-12
DA: lateral 1/3 clavicle, acromion, spine of scap
NS: CN XI accessory (motor), C3-4 spinal nerves (sensory)
Actions: elevation of the scapula, retraction of the scapula, depression of the scapula (each region respectively)

Platysma:
PA: subcutaneous tissue of supraclavicular & infraclavicular regions
DA: base of mandible, skin of cheek and lower lip, angle of mouth, and orbicularis oris
NS: CN VII facial
Actions: depresses mandible, tenses skin of inferior face and neck

Question 3

Describe the anatomy of the lateral neck muscles:

Answer 3

Scalene (posterior & middle):
PA: TPs C5-7
DA: middle: 1st rib, posterior: 2nd rib
NS: middle: anterior rami C5-7, posterior: anterior rami C7-8
Actions: elevation of 1st and 2nd rib, lateral flexion of the neck

Splenius capitis:
PA: inferior half of nuchal ligament, SPs T1-6
DA: mastoid process, lateral 1/3 superior nuchal line
NS: posterior rami of middle cervical spinal nerves
Actions: unilateral: ipsilateral lateral flexion and rotation of head and neck; bilateral: extension of head and neck

Levator scapulae:
PA: TPs C1-4
DA: medial border of scapula (superior to spine)
NS: dorsal scapular & C3-4 spinal nerves
Actions: elevates scap, rotates medial border of scapula superiorly

Rectus capitis lateralis:
PA: occipital bone (jugular process)
DA: TP of C1
NS: C1-2 spinal nerves
Actions: stabilizes & flexes head

Question 4

Describe the anatomy of the suprahyoid muscles

Answer 4

4 muscles:
Geniohyoid
Digastric
Mylohyoid
Stylohyoid

All originate from the mandible or temporal bone
All insert into the hyoid
All act on hyoid to aid swallowing and speaking functions

Innervated by CN V3 Trigeminal (mandible), CN XII Hypoglossal, and CN V88 Facial

PAs:
Geniohyoid - mandible
Digastric - anterior: mandible, posterior: mastoid notch
Myohyoid: mandible
Stylohyoid: styloid process

Question 5

Describe the anatomy of the infrahyoid muscles

Answer 5

SOTS
Sternohyoid
Omohyoid
Thyrohyoid
Sternothyroid

All insert into the hyoid
All act to depress and stabilize the hyoid, and act on the larynx

Innervated by ansa cervicalis and CN XII hypoglossal nerve

PAs:
Sternohyoid - manubrium
Omohyoid - superior border scapula
Thyrohyoid - thyroid cartilage
Sternothyroid - manubrium

Question 6

Describe the anatomy of the longus capitis and longus colli muscles

Answer 6

Longus capitis:
PA: occipital bone
DA: TPs C3-6

Longus colli:
PA: C1-6
DA: C3-T3

Innervated by anterior rami C2-6

Actions:
Longus colli - flexion of head only
Longus capitis - neck flexion (bilateral), ipsilateral rotation (bilateral)

Question 7

Describe the anatomy of the SCM

Answer 7

Two heads: sternal and clavicular

PA: sternal head - manubrium, clavicular head - medial 1/3 clavicle
DA: mastoid process temporal bone
NS: CN XI accessory

Actions:

unilateral: contralateral rotation of head
bilateral: neck flexion

Question 8

Describe the anatomy of the middle and posterior scalenes

Answer 8

PA: TPs C5-7
DA: middle - rib 1, posterior - rib 2
Actions: elevate rib 1 and 2, assist in respiration. unilateral contraction produces lateral flexion of the neck
NS: anterior rami Cx nerves (posterior C7-8 nerves only)

Question 9

Describe the anatomy of the sub-occipital muscles

Answer 9

There are 4 suboccipital muscles on each side of the cervical spine:

• rectus capitis posterior minor
• rectus capitis posterior major
• obliquus capitis superior
• obliquus capitis inferior

All insert into the inferior nuchal line except the obliquus capitis inferior, which inserts into the TP of C1
All are innervated by the suboccipital nerve

All act to stabilize the OA joint and stabilize the cranium on the cervical spine
The rectus capitis muscles extend and laterally flex the head
The rectus capitis posterior major also rotates the head

The obliquus capitis muscles rotate the head
The obliquus capitis superior also extends the head

Rectus capitis posterior major inserts onto the Sp of C2
Rectus capitis posterior minor inserts onto the posterior arch of C1

Obliquus capitis superior inserts onto the TP of C1
Obliquus capitis inferior inserts onto the SP of C1