1 Myology Muscles of the Anterior Neck

2 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.

3 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 (C0/C1) then it can move the head upon the neck.

4 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.

5 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.

6 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

7 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) Sternocleidomastoid (SCM) Palpation: Page 141

8 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

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

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

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

12 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 Omohyoid Palpation: page 155

13 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

14 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) Digastric Palpation: page 158

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

16 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) Mylohyoid Palpation: page 164

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

18 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.

19 O: Anterior tubercles of the TP’s of C3 – C6 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 Anterior Scalene Palpation: page 173

20 O: Posterior tubercles of the TP’s of C2 to C7 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 Middle Scalene Palpation: page 176

21 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 Posterior Scalene Palpation: page 179

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

23 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

24 O: Bodies of the C3-T3 vertebrae I: TP’s and Bodies of the C1-C6 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 Longus Colli For the purpose of HS 113, this muscle is not palpable

25 O: TP’s of C3 – C5 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 Longus Capitis For the purpose of HS 113, this muscle is not palpable

26 O: TP of the Atlas (C1) I: Inferior surface of the basilar portion of the occiput A: Flexion of head N: Ventral rami of the cervical spinal nerves Rectus Capitis Anterior For the purpose of HS 113, this muscle is not palpable

27 O: TP of the Atlas (C1) I: Inferior surface of the Occiput A: Lateral flexion of head N: Ventral rami of the cervical spinal nerves Rectus Capitis Lateralis For the purpose of HS 113, this muscle is not palpable