S1) General Organisation of the Head & Neck Flashcards
Describe the anatomical location of the neck
The neck extends from the lower margin of the mandible to the suprasternal notch of the manubrium and the upper border of the clavicle below
Which nerve innervates the trapezius?
Accessory nerve
A series of muscles attach above and below the hyoid bone.
Identify them and their nerve supply
- Supra‐hyoids supplied by cranial nerves
- Infra‐hyoids supplied by cervical nerves (C1‐3)
Identify the origins and attachments of the platysma
- Origin: lower mandible
- Attachment: chest wall
What are the actions and properties of the platysma?
- Property: superficial (lies in superficial cervical fascia)
- Action: depresses the corners of the mouth and draw down the mandible
The platysma is a muscle of facial expression.
In light of this, which nerve innervates it?
Facial nerve
Describe the origins and attachments of the sternocleidomastoid muscle
- Origin: mastoid process
- Attachment: sternum (sternal branch) and clavicle (clavicular branch)
What are the actions of the sternocleidomastoid muscle?
- Lateral flexion of the neck
- Head rotation
- Tilting chin up contralaterally
Which nerve innervates the sternocleidomastoid muscle?
Accessory nerve
Which muscle is contracted in the condition torticollis?
Sternocleidomastoid
What are the origins and attachments of the trapezius?
- Origins: external occipital protuberance and superior nuchal line
- Attachments: spine of scapula & lateral 1/3 of clavicle
What are the actions of the trapezius?
- Elevation of the shoulders (shrug)
- Rotate and retract the scapula
What happens when the accesory nerve is damaged?
Muscle wasting of the trapezius
The trapezius is innervated by the accesory nerve. How do we test the function of this nerve?
Test the actions of the trapezius muscle (shrug shoulders)
The anatomical borders divide the neck into two triangles.
Which borders form the anterior triangle?
- Inferior margin of the mandible
- Midline of the neck
- Anterior margin of sternocleidomastoid
The anatomical borders divide the neck into two triangles.
Which borders form the posterior triangle?
- Superior margin of clavicle
- Anterior margin of trapezius
- Posterior margin of sternocleidomastoid
What are the properties of the infra-hyoid muscles?
- Infra hyoids muscles are ‘strap‐like’ muscles
- They overlie the larynx and thyroid gland
What type of muscle is the omohyoid?
Infrahyoid
What type of muscle is the digastric muscle?
Suprahyoid muscle
Identify the carotid triangle
Which muscles form the carotid triangle?
- Omohyoid
- Sternocleidomastoid
- Digastric
What are the fascial planes of the neck?
Fascial planes are collections of structures enveloped in concentric fascial layers creating compartments running through the neck
What is the function of the cervical fascia?
- Forms natural planes
- Ease of movement between structures
- -* Contains spread of infection
What are the two forms of cervical fascia?
- Superficial cervical fascia: loose connective tissue (subcutaneous tissue)
- Deep cervical fascia: dense connective tissue
Describe the contents of the superficial cervical fascia
- Superficial blood vessels
- Cutaneous nerves
- Adipose tissue
- Lymph nodes
- Platysma
Describe the contents of the deep cervical fascia
- Investing layer (outer)
- Carotid sheath
- Pre tracheal fascia (intermediate)
- Pre vertebral fascia (deep)
Describe the superior, inferior and posterior attachments of the investing layer of the deep fascia
- Superior: lower border of the mandible, mastoid process, superior nuchal line and external occipital protuberance
- Inferior: upper border of manubrium, clavicle, acromion and spine of scapula
- Posterior: spinous process of the vertebrae and ligamentum nuchae
Describe the superior and inferior attachments of the pretracheal fascial layer
- Superior: hyoid bone
- Inferior: blends with fibrous pericardium in thorax
The pretracheal fascia consists of two layers.
Identify them and the structures they enclose
- Muscular layer which encloses the infrahyoid muscles
- Visceral layer which encloses the thyroid gland, trachea and oesophagus
What is the buccopharyngeal fascia and where is it found?
- The buccopharyngeal fascia is the posterior continuation of the pretracheal fascia to invest the muscles of the pharynx and oesophagus
- It extends from the base of the skull to the diaphragm
What is the carotid sheath and where is it found?
The carotid sheath is a fibrous structure which extends from the base of the skull inferiorly to the aortic arch
What are the contents of the carotid sheath?
- Common carotid artery
- Internal jugular vein
- Vagus nerve (CN X)
Describe the anatomical location of the prevertebral fascia
- Extends from the base of the cranium to the T3 vertebra
- Extends laterally as the axillary sheath that surrounds the axillary vessels and the brachial plexus
Identify and describe the two deep neck spaces that communicate with the mediastinum
- Retropharyngeal space (between prevertebral & buccopharyngeal fascia)
- Pre-tracheal space (in front of pretracheal fascia)
They extend inferiorly into the mediastinum
What is the danger with infections in the deep neck spaces?
Infections in the retropharyngeal and pretracheal spaces can potentially spread inferiorly to involve mediastinal structures (causing mediastinitus)
Identify the key structures related to the cervical fascia in the cross section of the neck below:
What are the two types of muscles of the face?
- Muscles of facial expression
- Muscles of mastication
Compare and contrast between muscles of facial expression and muscles of mastication in terms of action
- Muscles of facial expression: many act as dilators and sphinchters
- Muscles of mastication: act to open/close the jaw
Which nerve innervates the muscles of facial expression?
Facial nerve (CN VII)
Cranial nerve V is the trigeminal nerve.
What are its three branches?
- V1 opthalmic division
- V2 maxillary division
- V3 mandibular division
(V1-3 are also referred to as Va-c)
What are the motor and sensory functions of the trigeminal nerve?
- Main sensory nerve of the face and scalp
- Motor innervation to muscles of mastication
There are 5 key extra-cranial branches providing motor innervation to the muscles of facial expression.
What are they?
- Temporal
- Zygomatic
- Buccal
- Mandibular
- Cervical
Mnemonic: To Zanzibar By Motor Car
What is the main artery supply to the head and neck?
Common carotid artery is the main arterial supply by its terminal branches:
- Internal carotid artery
- External carotid artery
Compare and contrast the function of the internal and external jugular veins
- Internal jugular vein (IJV) provides venous drainage for the head and neck structures mainly
- External jugular vein (EJV) provides venous drainage for the scalp and face mainly (more superficial)
Identify a vein that drains into the internal jugular vein
Facial vein
In a patient with a retropharyngeal abscess, what might be expected with the extension of this infection to the deep neck space?
- Difficulty breathing due to tracheal compression
- Extension of infection into the mediastinum
- Painful or difficulty swallowing due to oesphageal compression
How can one test the function of the trigeminal nerve?
Ask the patient to open their mouth whilst you apply resistance under the jaw – note any deviation (jaw will deviate to side of lesion)
How can one test the function of the facial nerve?
- Assess patient’s face for any asymmetry
- Ask the patient to perform facial expressions and assess power of movements
What are the muscles of mastication?
- Temporalis
- Masseter
- Lateral pterygoid
- Medial pterygoid
State the action and innervation of the temporalis muscle
- Action: elevates and retracts the mandible at TMJ
- Innervation: mandibular branch (branch of trigeminal nerve)
State the action and innervation of the masseter muscle
- Action: elevates the mandible at TMJ (stronger than medial pterygoid)
- Innervation: mandibular nerve (branch of trigeminal nerve)
State the action and innervation of the lateral and medial pterygoids
- Action of lateral pterygoids: protract the mandible, ‘side to side’ movement of the jaw
- Action of medial pterygoids: elevates mandible at TMJ
- Innervation: mandibular nerve (branch of trigeminal nerve)
State the action and innervation of the buccinator muscle
- Action: flattens cheek & prevents food from pooling between cheek and gums
- Innervation: buccal branch of facial nerve
State the action and innervation of orbicularis oculi
- Action: inner palpebral part gently closes the eyelid, outer orbital part forcefully closes the eyelid
- Innervation: temporal and zygomatic branch of facial nerve
State the action and innervation of the orbicularis oris
- Action: closes mouth
- Innervation: buccal branch of facial nerve
The occipitofrontalis (frontalis and occipitalis) and its aponeurosis form one of the layers of the scalp.
State its action and innervation
- Action: elevates eyebrows
- Innervation: frontal belly (temporal branch of facial nerve) and occipital belly (posterior auricular branch)
State the action and innervation of levator palpebrae superioris
- Action: elevates upper eyelid
- Innervation: oculomotor nerve
What is Bell’s palsy?
- Bell’s palsy is the inflammation of the facial nerve causing oedema and compression of the nerve as it runs through its bony canal within the temporal bone
- This causes facial paralysis on the ipsilateral side of the injury
Where can the facial pulse be palpated?
The pulse of the facial artery can be palpated as the artery winds around the inferior border of the mandible
