Muscles of the head and neck NOT DONE

Action and innervation of the sternocleidomastoid

Unilateral = contralateral rotation (right sided contraction → head moves left)

Bilateral = flexion

Innervation: Accessory nerve (CN XI)

How do approximate the accessory nerve?

In the posterior triangle

Approx. 1/3 down SCM to 1/3 up trapezius

What are the Suboccipital muscles?

Rectus capitis posterior major: C2 spinous process to lateral inf. NL

Rectus capitis posterior major: Post. tubercle C1 to medial inf. NL

Obliquus capitis superior: C2 spine to C1 transverse process

Obliquus capitis inferior: C1 (TP) to occiput laterally

Insertion of the trapezius muscle

From sup. nuchal line + nuchal ligament to scapula spine, acromion + lateral 1/3 clavicle

Action and innervation of the trapezius muscle

unilateral contraction: lateral flexion and contralateral rotation of the head

bilateral contraction: extension of the head

Innervation: Accessory nerve (CN XI)

Origin and insertion of the scalene muscles

Posterior: Post. tubercles C5-7 to 2nd rib

Middle: Post. tubercles C2-7 to 1st rib

Anterior: Ant. tubercles C3-6 to 1st rib (scalene tubercle)

Action of the scalene muscles

Anterior:

• Elevation of the first rib

• Ipsilateral contraction causes ipsilateral lateral flexion of the neck

• bilateral contraction causes anterior flexion of the neck

Middle:

• Elevation of the first rib

• Ipsilateral contraction causes ipsilateral lateral flexion of the neck

Posterior:

• Elevation of the second rib

• ipsilateral lateral flexion of the neck

Innervation of the scalene muscles

Anterior: Anterior rami of C5-C6

Middle: Anterior rami of C3-C8

Posterior: Anterior rami of C6-C8

What passes between the anterior and middle scalene?

The brachial plexus and subclavian artery

What passes the anterior scalene?

subclavian vein and phrenic nerve pass anteriorly to the anterior scalene

subclavian vein courses horizontally across it

the phrenic nerve runs vertically down the muscle

What is the function of the splenius muscles?

Unilateral contraction: lateral flexion and ipsilateral rotation of the head and neck

Bilateral contraction: extension of the head and neck

What are the 2 splenius muscles?

Splenius capitis and cervicis

Action and innervation of the longus colli muscle

Bilateral contraction: Neck flexion

Unilateral contraction: Neck contralateral rotation, neck lateral flexion (ipsilateral)

Innervation: Anterior rami of spinal nerves C2-C6

Action and innervation of the Longus capitis muscle

Bilateral contraction - head flexion

Unilateral contraction - head rotation (ipsilateral)

Innervation: Anterior rami of spinal nerves C1-C3

Name the Prevertebral muscles

longus capitis

longus colli

rectus capitis anterior

rectus capitis lateralis

Actions and innervation of the oribucularis oculi

Palpebral part – gently closes the eyelids.

Lacrimal part – involved in the drainage of tears.

Orbital part – tightly closes the eyelids

Innervation: Temporal and zygomatic branches of the facial nerve

Action and innervation of the Corrugator Supercilii

Draws the eyebrows together, creating vertical wrinkles on the bridge of the nose (associated with frowning)

Innervation: Temporal branches of the facial nerve

Action and innervation of the Orbicularis Oris

Closes the lips to narrow the oral opening

Innervation: Buccal branches of the facial nerve

Action and innervation of the buccinator muscle

Pulls the cheek inwards against the teeth, preventing accumulation of food in that area

Innervation: Buccal branches of the facial nerve

Action and innervation of the platysma muscle

Depresses mandible and angle of mouth, tenses skin of lower face and anterior neck

Innervation: Cervical branch of facial nerve (CN VII)

Location of the pharyngeal constrictors

Superior constrictor

• Posterior: from base of occiput

• Anterior: from mandible, pterygomandibular ligament, + pterygoid hamulus

• Inserts as a midline raphe

Middle constrictor

• From hyoid bone + stylohyoid ligament

• Inserts as a midline raphe

Inferior constrictor – two parts:

• Thyropharyngeus: from thyroid cartilage

• Cricopharyngeus: from cricoid cartilage

What is Killian’s dehiscence?

weakness between the 2 inferior pharyngeal constrictors

The herniation of mucosa through Killian's dehiscence results in a Zenker's diverticulum (or pharyngeal pouch) → dysphagia, regurgitation, halitosis, cough

Innervation to the pharyngeal muscles

All muscles of the pharynx = CN X

Except stylopharyngeus = CN IX

Except Thyropharyngeus = CN Vc

What are the muscles of mastication and their action and innervation

Four muscles – move the TMJ:

• Masseter – elevates

• Temporalis – elevates and retracts

• Medial pterygoid – elevates

• Lateral pterygoid – protracts

Innervated: Mandibular nerve (CN V3)

Name the intrinsic muscles of the tongue and their innervation

Superior and inferior longitudinal

Transverse

Vertical

Innervation: hypoglossal nerve (CN XII)

Name the extrinsic muscles of the tongue and their innervation

Genioglossus

Hyoglossus

Styloglossus

Palatoglossus

Innervation: hypoglossal nerve (CN XII), except palatoglossus innervated by vagus nerve (CN X) (via branches of pharyngeal plexus)

Action of the intrinsic tongue muscles

Superior and inferior longitudinal: retracts and broadens tongue, elevates (superior) / lowers (inferior) apex of tongue

Transverse: narrows and elongates tongue

Vertical: broadens and elongates tongue

Action of the extrinsic tongue muscles

Genioglossus: depresses and protrudes tongue (bilateral contraction); deviates tongue contralaterally (unilateral contraction)

Hyoglossus: depresses and retracts tongue

Styloglossus: retracts and elevates lateral aspects of tongue

Palatoglossus: elevates root of tongue, constricts isthmus of fauce

What are the Suprahyoid muscles and their actions?

Digastric

Stylohyoid

Mylohyoid

Geniohyoid

Action: elevate the hyoid

What innervates the suprahyoid muscles

Digastric:

• Anterior belly: Nerve to mylohyoid (of inferior alveolar nerve (CN V3))

• Posterior belly: Digastric branch of facial nerve (CN VII)

Stylohyoid:

• Stylohyoid branch of facial nerve (CN VII)

Mylohyoid:

• Nerve to mylohyoid (of inferior alveolar nerve (CN V3))

Geniohyoid:

• Anterior ramus of spinal nerve C1 (via hypoglossal nerve CN XII))

Name the infrahyoid muscles and their actions

Omohyoid (sup. and inf. bellies)

Sternothyroid: + depresses larynx

Thyrohyoid: + elevates larynx

Sternohyoid

Action: depress the hyoid

Innervation to the infrahyoid muscles

Anterior rami of spinal nerves C1-C3 (via ansa cervicalis):

• Nerve to Omohyoid (sup. and inf. bellies)

• Nerve to Sternothyroid

• Nerve to Sternohyoid

Anterior ramus of spinal nerve C1 (via hypoglossal nerve):

Nerve to Thyrohyoid