muscles of head and neck

muscles of facial expression

• epicranius

• orbicularis oculi

• orbicularis oris

• buccinator

• zygomatic minor and major

• platysma

epicranius (occipito-frontails)

origin: occipital bone

insertion: skin above eye

action: raises eyebrow

nerve supply: facial nerve

obricularis oculi

origin: maxilla and frontal bone

insertion: skin around eye

action: blinking

nerve supply: facial nerve

orbicularis oris

origin: near mouth

insertion: skin around lips

action: closes lips

nerve supply: facial

buccinator

origin: alveolar processes of maxilla and mandible

insertion: orbicularis oris

action: compresses cheeks

nerve supply: facial nerve

zygoamtic major

origin: zygomatic bone

insertion: skin and muscle at corner of mouth

action: smiling

nerve supply: facial nerve

zygoamtic minor

origin: zygomatic bone

insertion: skin and muscle at corner of mouth

action: smiling

nerve supply: facial nerve

platysma

origin: fascia in upper chest

insertion: skin and muscles below mouth/ mandible

action: pouting

nerve supply: facial nerve

bell’s palsy

• Scientific name: acute idiopathic peripheral facial nerve (CN VII) palsy

• Cause: idiopathic because a specific cause cannot always be identified

Muscles of mastication

1. Masseter

2. Temporalis

3. Medial pterygoid

4. Lateral pterygoid

Masseter

origin: zygomatic arch

insertion: Lateral surface of ramus and angle of mandible

nerve supply: Masseteric nerve (V3)

Temporalis

origin: Temporal fossa and deep surface of temporal fascia

insertion: Coronoid process and anterior border of ramus

nerve supply: Deep temporal nerves (V3)

Medial pterygoid

origin: Medial surface of lateral pterygoid plate; maxillary tuberosity/pyramidal process of palatine bone

insertion: Medial surface of angle and ramus of mandible

nerve supply:Nerve to medial pterygoid (V3)

origin: Greater wing of sphenoid (superior head); lateral surface of lateral pterygoid plate

Insertion: Neck of mandible at pterygoid fovea; TMJ capsule and articular disc

Nerve supply: Nerve to lateral pterygoid (V3)

extraocular muscles

• Superior rectus

• Inferior rectus

• Medial rectus

• Lateral rectus

• Superior oblique

• Inferior oblique

What is the common origin of the 4 recti muscles?

common tendinous ring (annulus of Zinn) at the apex of the orbit

Where do all 6 muscles insert?

onto the globe of the eye

sup. rectus

nerve: oculomotor ( CN III)

main action: elevates, adducts eye

inf. rectus

nerve: oculomotor (CN III)

main action: depresses, adducts eye

medial rectus

nerve: oculomotor (CN III)

main action:adducts eye

lateral rectus

nerve: abducens (CN VI)

main action: abducts eye

sup. oblique

nerve: trochlear

main action: depresses, abducts eye

inf. oblique

nerve: oculomotor(CN III)

main action: elevates, abducts eye

Strabismus

condition in which the two eyes are not properly aligned, so they do not simultaneously point toward the same visual target ( lazy eye)

2 kinds of tongue muscles

1. Intrinsic muscles

2. Extrinsic muscles

   
   

Intrinsic muscles

These muscles are contained entirely within the tongue

Their primary function is to change the tongue’s shape.

Extrinsic muscles

These muscles originate outside the tongue and insert into the tongue.

Their primary function is to move the tongue as a whole.

4 extrinsic tongue muscles

1. Genioglossus

2. Hyoglossus

3. Styloglossus

4. Palatoglossus

Genioglossus

Origin: Superior mental spine (genial tubercle) of mandible

Insertion: Entire length of tongue, from inferior portion to tip; some fibers attach to hyoid

Nerve: Hypoglossal nerve (CN XII)

Action: Protrudes tongue; inferior fibers can depress the tongue

Hyoglossus

Origin: Body and greater horn of hyoid bone

Insertion: Lateral side of tongue

Nerve: Hypoglossal nerve(CN XII)

Action: Depresses and retracts tongue

Styloglossus

Origin: Styloid process of temporal bone and stylohyoid ligament Insertion: Lateral side of tongue

Nerve: Hypoglossal nerve (CN XII)

Action: Retracts and elevates tongue

Palatoglossus

Origin: Palatine aponeurosis

Insertion: Lateral tongue

Nerve: Vagus nerve (CN X) via pharyngeal plexus

Action: Elevates posterior tongue and helps depress the soft palate; narrows the oropharyngeal opening

What is the most superior muscle in the anterior neck? Does it move the neck?

• sternocleidomastoid (SCM)

• Yes. It is an important muscle for neck movement and head positioning

Which muscle divides the anterior neck into an anterior and a lateral triangle?

Sternocleidomastoid muscle (SCM)

Sternocleidomastoid origin

Sternal head: anterior surface of manubrium of sternum

Clavicular head: superior surface of medial clavicle

Sternocleidomastoid insertion

Mastoid process of temporal bone and lateral half of superior nuchal line

Sternocleidomastoid nerve supply

Spinal accessory nerve (CN XI) for motor; C2–C3 for proprioception/ sensory

Sternocleidomastoid Unilateral action

Ipsilateral lateral flexion + contralateral rotation of the head

Sternocleidomastoid Bilateral action

Flexes the neck/cervical spine; can also extend the head at the atlanto-occipital joint depending on the starting position

Congenital muscular torticollis

condition in which the SCM is shortened/tight, causing the infant's head to be tilted to one side and the chin to turn toward the opposite side.

laymen’s name

wrey neck or twisted neck

Suprahyoid muscles

Located above the hyoid.

Main muscles:

• Digastric

• Mylohyoid

• Stylohyoid

• Geniohyoid

function of suprahyoid muscles

elevate the hyoid and larynx during swallowing and assist with opening the mouth

infrohyoid muscles

Located below the hyoid.

Main muscles:

• Sternohyoid

• Omohyoid

• Sternothyroid

• Thyrohyoid

infrahyoid msucle function

generally depress/stabilize the hyoid and larynx, particularly after swallowing

Which muscle is the most superficial muscle in the posterior aspect of the neck?

Trapezius

Which muscles are in the middle layer of the posterior aspect of the neck?

• Splenius capitis

• Splenius cervicis

These are collectively called the splenius muscles

Splenius capitis origin

Lower half of ligamentum nuchae and spinous processes of C7–T3/T4

Splenius capitis insertion

Mastoid process of temporal bone and lateral third of superior nuchal line

Splenius capitis nerve supply

Posterior rami of cervical spinal nerves

Splenius capitis unilateral action

Ipsilateral rotation and lateral flexion of the head/neck

Splenius capitis bilateral action

Extension of the head and neck

Which muscles are the deepest muscles in the posterior aspect of the neck?

1. Rectus capitis posterior major

2. Rectus capitis posterior minor

3. Obliquus capitis superior

4. Obliquus capitis inferior

Known as the suboccipital muscles

Suboccipital triangle

• Is an anatomical space in the deep posterior neck

• Clinically important because the vertebral artery passes through it