Myology Muscles of the Anterior Neck 1 Muscles

Myology Muscles of the Anterior Neck 1

Muscles of the Neck Overview • Muscle of neck are divided into two groups: – Anterior • Superficial (2) • Hyoids – Infrahyoids (4) – Suprahyoids (4) • Scalenes (3) • Deep (4) – Posterior • Superficial (4) • Deep (4) • Note: Some sources divide neck into anterior, posterior, & lateral. 2

Muscles of Neck Overview • Functionality – Since these muscles cross the joints of the cervical spine, they can move the neck at the cervical spinal joints – If a muscle also crosses the atlanto-occipital joint (C 0/C 1) then it can move the head upon the neck. 3

Muscles of Neck Overview • General Rules: – If a muscle crosses the neck posteriorly, it can extend the neck at the cervical spinal joints. – If a muscle crosses the neck anteriorly, it can flex the neck at the cervical spinal joints. – If a muscle crosses the neck laterally, it can laterally flex the neck at the cervical spinal joints. – If a muscle wraps around the neck, it can cause rotation of the neck at the cervical spinal joints. 4

Muscles of the Anterior Neck – Superficial (2) • Platysma : – By function it is primarily a muscle of facial expression i. e. innervated by CN VII. – Platysma of one side blends with contralateral side and other facial muscles in lower face. – Considered to by remnant of a broader muscle called panniculus carnosus found in four-legged animals. Enables horses to shake off flies and cats to raise hair on its back. – When contracted it is reminiscent of “Creature from the Black Lagoon” creature. • Sternocleidomastoid (SCM): – Since it attaches to sternum, SCM is considered an accessory muscle of respiration. 5

Platysma O: Subcutaneous Fascia of Superior Chest I: Mandible and subcutaneous fascia of lower face A: Draws up the skin of superior chest and neck, creating ridges in neck skin. Assists in drawing the lip laterally and depresses the mandible N: CN VII (Facial nerve) Palpation: Page 138 6

Sternocleidomastoid (SCM) O: Sternal Head: manubrium Clavicular Head: Medial clavicle I: Mastoid process Actions: Bilateral contraction: flexion of the neck. Unilateral contraction results in Lateral flexion of neck/head and Contralateral rotation of neck/head N: Spinal accessory nerve (CN XI) Palpation: Page 141 7

Muscles of the Anterior Neck – Infrahyoids (4) • All 4 infrahyoid muscles are located below the hyoid bone i. e. the pull hyoid bone inferiorly when contracted. • All hyoid muscle are important in moving and/or fixating the hyoid bone. These functions are necessary for chewing, swallowing, & speech. • Sternohyoid: – “Sterno” refers to sternum – “hyoid” refers to hyoid bone • Sternothyroid: – “thyroid” refers to thyroid cartilage • Thyrohyoid • Omohyoid: – “Omo” refers to the shoulder 8

Sternohyoid O: Posterior aspect of the manubrium and medial clavicle I: Inferior Hyoid A: Depression of hyoid N: Ansa cervicalis of the cervical plexus Palpation: page 147 9

Sternothyroid O: Posterior Sternum and 1 st costal cartilage I: Thyroid Cartilage A: Depression of thyroid cartilage N: Ansa cervicalis of the cervical plexus Palpation: page 150 10

Thyrohyoid O: Thyroid Cartilage I: Hyoid (inferior aspect) A: Depression of hyoid and Elevation of thyroid cartilage N: CN XII (Hypoglossal nerve) Palpation: page 152 11

Omohyoid O: Inferior Belly: Superior angle of the scapula Superior Belly: Clavicle via the central bound to the clavicle I: Inferior belly: Clavicle (via the central bound to the clavicle) Superior belly: hyoid A: Depression of hyoid N: Ansa cervicalis of the cervical plexus Palpation: page 155 12

Muscles of the Anterior Neck – Suprahyoids (4) • Digastric: – “Di” means two; “gastric” means belly – External carotid lies inferior and deep to anterior belly • Stylohyoid: – External carotid lies inferior and deep to stylohyoid • Mylohyoid: – “mill” refers to molar teeth • Geniohyoid: – “genio” refers to chin 13

Digastric O: Posterior belly: mastoid notch of temporal bone Anterior belly: Inner surface of the mandible I: Hyoid (via the central tendon) A: Elevation of hyoid, depression of the mandible, and retraction of the mandible. N: anterior belly: CN V (Trigeminal nerve) posterior belly CN VII (Facial nerve) Palpation: page 158 14

Stylohyoid O: Styloid process of temporal bone I: Hyoid Actions: Elevation of hyoid N: CN VII (Facial nerve) Palpation: page 161 15

Mylohyoid O: Entire inner surface of mandible (this muscle forms the muscular floor of the mouth) I: Hyoid A: Elevation of hyoid and depresses the mandible N: CN V (Trigeminal nerve) Palpation: page 164 16

Geniohyoid O: Inner surface of mandible, deep to the mylohyoid I: Hyoid A: Elevation of hyoid N: CN XII (Hypoglossal nerve) Palpation: page 167 17

Muscles of the Anterior Neck – Scalenes (3) • As a group, they attach superiorly from cervical TP's to inferiorly on the 1 st and 2 nd ribs • As a group, scalenes flex and laterally flex the neck • By reverse muscles action, the scalenes can elevated the 1 st & 2 nd rib i. e. they are also considered accessory muscle of respiration. 18

Anterior Scalene O: Anterior tubercles of the TP’s of C 3 – C 6 I: 1 st Rib A: Bilateral contraction: flexion of the neck. Unilateral contraction causes lateral flexion and contralateral rotation of the neck. Reversed muscle action causes Elevation of 1 st rib N: Ventral rami of the cervical spinal nerves Palpation: page 173 19

Middle Scalene O: Posterior tubercles of the TP’s of C 2 to C 7 I: 1 st Rib A: Bilateral contraction: flexion of the neck. Unilateral contraction causes lateral flexion of the neck. Reversed muscle action causes Elevation of 1 st rib N: Ventral rami of the cervical spinal nerves Palpation: page 176 20

Posterior Scalene O: Posterior tubercles of the TP’s of cervical spine I: 2 nd Rib A: Unilateral contraction causes lateral flexion of the neck. Reversed muscle action causes Elevation of 2 nd rib N: Ventral rami of the cervical spinal nerves Palpation: page 179 21

The Scalene Group • Scalenes, as well as SCM, are often injured during MVA called whiplash. • Also known as cervical acceleration deceleration (CAD) injury 22

Muscles of the Anterior Neck – Deep Prevertebral Group (4) • Called prevertebral muscles since they lie directly on the cervical spine vertebral bodies • Important at fixating (stabilizing) and neck/head while talking, swallowing, coughing, & sneezing • May also be injured during CAD • Longus Colli: – Has 3 parts: superior oblique, inferior oblique, & vertical – Considered to be a strong neck flexor • Longus Capitis • Rectus Capitis Anterior • Rectus Capitis Lateralis 23

Longus Colli O: Bodies of the C 3 -T 3 vertebrae I: TP’s and Bodies of the C 1 -C 6 vertebrae A: Bilateral contraction causes weak flexion of neck. Unilateral contraction causes lateral flexion and contralateral rotation of the neck. N: Ventral rami of the cervical spinal nerves For the purpose of HS 113, this muscle is not palpable 24

Longus Capitis O: TP’s of C 3 – C 5 I: Basilar portion of the occiput A: Bilateral contraction causes Flexion of head/neck. Unilateral contraction causes Lateral flexion of head/neck N: Ventral rami of the cervical spinal nerves For the purpose of HS 113, this muscle is not palpable 25

Rectus Capitis Anterior O: TP of the Atlas (C 1) I: Inferior surface of the basilar portion of the occiput A: Flexion of head N: Ventral rami of the cervical spinal nerves For the purpose of HS 113, this muscle is not palpable 26

Rectus Capitis Lateralis O: TP of the Atlas (C 1) I: Inferior surface of the Occiput A: Lateral flexion of head N: Ventral rami of the cervical spinal nerves For the purpose of HS 113, this muscle is not palpable 27