Muscle Basics
MUSCLES
OF THE HEAD AND NECK
• Muscles either work together
(synergistic) or they work oppositely
(antagonistic)
• The “origin” if the muscle is the fixed end
• The “insertion” of the muscle is the
movable end
• When the muscle contracts, it pulls the
“insertion” towards the “origin”
Origin Insertion
Category of
Muscles
• The sarcomere
is the Basics
contractor in a
Muscle
muscle
• A chain of sarcomeres make up a
myofibril
• The sarcomere “voluntarily” contracts
when we purposefully stimulate it, or
• It contracts automatically
(involuntarily).
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Muscles of Facial Expression
(Basics)
All facial muscles innervated by
the seventh cranial nerve
Blood supply to facial muscles
From the facial artery (off the
external carotid)
Both cross the notch on the lower
border of the mandible, a good
pressure spot to stop bleeding
Facial expression
Mastication
Cervical
Hyoid
Pharyngeal
Muscles of Facial Expression
(Basics)
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Depressors pull down
Levator’s pull up
Orbicularis circle
All muscles are paired and
bilateral except oris
1
Obicularis oris (pucker)
Levator anguli oris (smile)
Buccinator (food pusher)
Epicranial (surprise)
Zygomaticus major and minor,
(Smiling, raising upper lip)
Obicularis oculi (close eye)
Depressor anguli oris (frown)
Risorius (wide smile)
Levator labii (raise lip)
Procerus (wrinkles bridge)
Bell’s Palsy
Paralysis of the facial nerve caused by
trauma, infection, other causes
Mentalis (pout)
Platysma (grimace)
Corrugator supercilli (frown)
Muscles of Mastication
• Innervated by mandibular branch of
trigeminal nerve
• 4 pairs - Medial, lateral pterygoid, masseter,
temporal
• Masseter, medial pterygoid elevate mandible
• Temporal elevates and retrudes mandible
• Lateral pterygoid protrudes both the
mandible and articular disc and causes lateral
excursions, depresses mandible slightly
Muscles of Mastication
Masseter m. elevates mandible
Origin – zygomatic arch,
Insertion - lower border
of the mandible
Buccinator NOT a muscle of mastication, it pushes food onto
the chewing surface (occlusal table)
Temporal M. retrudes and
elevates mandible
Origin – temporal fossa
Insertion – coronoid process
Temporal M. passes medial
to the zygomatic arch
2
Lateral pterygoid
Lateral pterygoid
• Lateral pterygoid has
two heads, inferior
and superior
• Inferior head goes
from pterygoid plate
to head of condyle
• When inferior head
contracts, it pulls
condyle forward and
depresses it slightly
(inferior head)
When only one lateral
pterygoid contracts, the
mandible moves to the side
(lateral excursion)
Which lateral pterygoid
contracted?
Lateral pterygoid
Lateral pterygoid
(inferior head)
(superior head)
Articular disc is a fibrous
pad that acts as a cushion
for TMJ
When both lateral pterygoids
contact, the mandible moves
forward (protrusion)
Superior head inserts
into articular disc
When the mouth is
opened wide, the condyle
moves forward, the
superior head pulls
articular disc forward
to protect joint
Inferior head
Cervical Muscles
Hyoid Muscles
Trapezius shrugs shoulders
Platysma supports neck
Sternocleidomastoid supports
head, pulls it down, interferes
with palpation of lymph nodes
Hyoid is u shaped bone
suspended under mandible
Infrahyoid muscles originate on
sternum, thyroid. They stabilize
hyoid so mandible can pull on it
Suprahyoid muscles pull against
hyoid, depress mandible
3
Suprahyoid Muscles
Digastric has two bellies, anterior is
innervated by trigeminal(V) , posterior
is innervated by facial(VII)
Mylohyoid forms floor of mouth,
attaches to hyoid at midline
Infrahyoid Muscles
• Comprised of
sternothyroid, sternohyoid,
omohyoid and thyrohyoid
• Stabilize hyoid so
suprahyoid muscles can
pull against it.
Stylohyoid runs posteriorly to
styloid process
Geniohyoid inserts into genial
tubercles
Pharyngeal Muscles
• Levator veli palatini closes off nasopharynx
• Stylopharyngeus muscle widens oropharynx
• Pharyngeal constrictor muscles force food
inferiorly
• Tensor veli palatini stiffens soft palate
• Palatoglossus forms anterior faucial pillar
Palatopharyngeus forms posterior faucial pillar
4