Download 06 – Muscles of the Anterior Neck

Myology
Muscles of the
Anterior Neck
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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.
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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.
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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.
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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.
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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
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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
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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
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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
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Sternothyroid
O: Posterior Sternum and 1st
costal cartilage
I: Thyroid Cartilage
A: Depression of thyroid
cartilage
N: Ansa cervicalis of the
cervical plexus
Palpation: page 150
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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
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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
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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
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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
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Stylohyoid
O: Styloid process of temporal
bone
I: Hyoid
Actions: Elevation of hyoid
N: CN VII (Facial nerve)
Palpation: page 161
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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
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Geniohyoid
O: Inner surface of mandible,
deep to the mylohyoid
I: Hyoid
A: Elevation of hyoid
N: CN XII (Hypoglossal nerve)
Palpation: page 167
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Muscles of the Anterior Neck –
Scalenes (3)
• As a group, they attach superiorly from cervical TP's to
inferiorly on the 1st and 2nd ribs
• As a group, scalenes flex and laterally flex the neck
• By reverse muscles action, the scalenes can elevated the 1st
& 2nd rib i.e. they are also considered accessory muscle of
respiration.
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Anterior Scalene
O: Anterior tubercles of the
TP’s of C3 – C6
I: 1st 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 1st rib
N: Ventral rami of the cervical
spinal nerves
Palpation: page 173
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Middle Scalene
O: Posterior tubercles of the
TP’s of C2 to C7
I: 1st Rib
A: Bilateral contraction:
flexion of the neck.
Unilateral contraction causes
lateral flexion of the neck.
Reversed muscle action
causes Elevation of 1st rib
N: Ventral rami of the cervical
spinal nerves
Palpation: page 176
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Posterior Scalene
O: Posterior tubercles of the TP’s of
cervical spine
I: 2nd Rib
A: Unilateral contraction causes lateral
flexion of the neck.
Reversed muscle action causes
Elevation of 2nd rib
N: Ventral rami of the cervical spinal
nerves
Palpation: page 179
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The Scalene Group
• Scalenes, as well as
SCM, are often
injured during MVA
called whiplash.
• Also known as
cervical acceleration
deceleration (CAD)
injury
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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
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Longus Colli
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
For the purpose of HS 113, this muscle is not
palpable
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Longus Capitis
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
For the purpose of HS 113, this muscle is not
palpable
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Rectus Capitis Anterior
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
For the purpose of HS 113, this muscle is not
palpable
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Rectus Capitis Lateralis
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
For the purpose of HS 113, this muscle is not
palpable
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