Anaesthetics: Anatomy - Neck Flashcards
What is unique about the hyoid bone?
Does not articulate with any other bone
What is the usual mechanism of hyoid fracture?
Strangulation
What is the function of the hyoid?
Provides attachment for anterior neck muscles
Holds airway open
What is a possible complication of hyoid fracture?
Difficulty maintaining separation of respiratory and alimentary tracts when swallowing, leading to increased risk of aspiration pneumonia
What is the vertebral level of the hard palate?
C1
What is the vertebral level of the lower border of the mandible?
C2-3
What is the vertebral level of the hyoid?
C3
What is the vertebral level of the cricoid?
C6
Six contents of the superficial cervical fascia
- Cutaneous nerves
- Bloods vessels
- Lymphatic vessels
- Superficial lymph nodes
- Fat
- Platysma
What are the three layers of the deep cervical fascia, from superficial to deep?
- Investing layer
- Pretracheal fascia
- Prevertebral fascia
What is the embryological origin of the platysma?
Arises from mesenchyme in the 2nd pharyngeal arch
Where does the platysma arise and insert?
Fibres arise from deep fascia of upper parts of pectoralis major and deltoid, and run to inferior border of mandible
Diverge inferior to chin, leaving gap anterior to larynx and trachea
Which neurovascular structures are deep to the platysma in the superficial cervical fascia?
Main cutaneous nerves
External and anterior jugular
Describe the course of anterior jugular vein
Commences beneath the chin, continues down to suprasternal region then pierces deep fascia and lies in suprasternal space (often connected by short anastomotic vein)
Describe the motor and sensory nerve supply of the platysma
Motor supply from cervical branch of facial nerve
Sensory (proprioceptive) fibres run with transverse cervical nerve
What are the actions of the platysma?
Muscle of facial expression (tension, stress)
May help open mouth
What is the clinical presentation of platysma muscle paralysis?
Due to palsy of cervical branch of facial nerve
Skin falls away from neck in slack folds
Where does the investing layer of the deep cervical fascia split and why?
Splits at all four corners into superficial and deep layers to enclose sternocleidomastoid (anterolaterally) and trapezius (posterolaterally)
Six superior attachments of the investing layer of the deep cervical fascia
- Superior nuchal line of occipital bone
- Mastoid processes
- Zygomatic arches
- Inferior border of mandible
- Hyoid bone
- Spinous processes of cervical vertebrae
Three inferior attachments of the investing layer of the deep cervical fascia
- Manubrium
- Clavicles
- Acromions and spines of scapulae
Where does the investing layer of the deep cervical fascia split? What extensions does it have?
Inferior to mandible to enclose submandibular gland
Posterior to mandible to enclose parotid gland
Superior to manubrium to enclose sternocleidomastoid (forms suprasternal space)
Extends as stylomandibular ligament
How is the suprasternal space formed and what does it contain?
Between layers of the investing layer of deep cervical fascia as it splits to enclose sternocleidomastoid: superficial layer attaches to anterior manubrium, deep layer to posterior manubrium, forming suprasternal space
Contains anterior jugular veins, jugular venous arch, fat, and few deep lymph nodes
What are the two parts of the pretracheal fascia and what does each enclose?
Muscular part: encloses infrahyoid muscles (sternothyroid, sternohyoid, omohyoid)
Visceral part: encloses thyroid gland, trachea, oesophagus
What is the visceral part of the pretracheal fascia continuous with?
Superiorly and posteriorly with buccopharyngeal fascia
How does the omohyoid suspend the hyoid?
Intermediate tendon passes through a thickening of the pretracheal fascia superior to the hyoid, forming a pulley and suspending the hyoid
What happens to the pretracheal fascia at its lateral and inferior borders?
Laterally blends with fibres of the carotid sheath
Inferiorly passes behind brachiocephalic veins and is continuous with fibrous pericardium
What is enclosed within the prevertebral fascia?
Vertebral column and associated muscles:
- Longus coli and longus capitis anteriorly
- Scalenes laterally
- Deep cervical muscles posteriorly
Describe the boundaries of the pretracheal fascia
Fixed to cranial base superiorly
Blends with endothoracic fascia and anteriorly longitudinal ligament (at approx T3) inferiorly
Extends laterally as axillary sheath
What structures are embedded in the prevertebral fascia?
Cervical parts of sympathetic trunks
What part of the subclavian artery lies deep to the prevertebral fascia?
Third part
Which nerves pierce the prevertebral fascia?
Cutaneous branches of cervical plexus:
- Greater auricular
- Lesser occipital
- Transverse cervical
- Supraclavicular
Where does the carotid sheath run?
Between cranial base to root of neck
Blends anteriorly with investing layer and pretracheal fascia, and posteriorly with prevertebral fascia
Contents of the carotid sheath
I C 10 CC’s in the IV:
- Internal Carotid
- CN 10 (vagus)
- Common Carotid
- Internal jugular Vein
- Some deep cervical lymph nodes
- Carotid sinus nerve
- Sympathetic nerve fibres (carotid peri-arterial plexuses)
What is the retropharyngeal space?
Potential space between superior part of the prevertebral fascia and the buccopharyngeal fascia
Further subdivided by alar fascia, which is attached along the midline of the buccopharyngeal fascia from cranium to C7, then extends laterally to terminate in the carotid sheath
What is the function of the retropharyngeal space?
Permits movement of viscera (pharynx, larynx, oesophagus, trachea) relative to vertebral column with swallowing
What is the retropharyngeal space continuous with and what is the clinical significance of this?
Continuous inferiorly with superior mediastinum
Retropharyngeal space infection can extend into superior mediastinum
How can infections in the head and neck extend into the mediastinum?
Posterior mediastinum: from head tracks down posterior to oesophagus
Anterior mediastinum: from head tracks down anterior to trachea, or if infection from neck enters space between investing layer and visceral part of the pretracheal fascia
Can infection between the investing layer and muscular part of the pretracheal fascia spread into the mediastinum?
No, cannot spread beyond superior border of manubrium (unless perforates into visceral part of pretracheal fascia)
Attachments, innervation and actions of platysma
Superior attachment: inferior mandible, skin and subcut tissue of lower face
Inferior attachment: deep fascia of upper parts of pec major and deltoids
Innervation: cervical branch of CN VII
Actions: facial expression
Three cutaneous/superficial muscles of the neck
- Platysma
- Sternocleidomastoid
- Trapezius
Four suprahyoid muscles from superficial to deep
- Digastric
- Stylohyoid
- Mylohyoid
- Geniohyoid
Four infrahyoid muscles from superficial to deep
- Sternohyoid
- Omohyoid
- Sternothyroid
- Thyrohyoid
Attachments, innervation and actions of sternocleidomastoid
Superior attachment: mastoid process and lateral superior nuchal line
Inferior attachment: sternal head to manubrium, clavicular head to medial 1/3 of clavicle
Innervation: CN XI (motor), C3-4 (pain, proprioception)
Actions: unilateral does lateral neck flexion with head turned to opposite side, bilateral does neck flexion at atlanto-occipital joint as well as chin-to-chest action and chin protrusion, also assists respiration
Attachments, innervation and actions of trapezius
Medial attachments: medial superior nuchal line, occipital protuberance, nuchal ligament, C7-T12 and lumbosacral spinous processes
Lateral attachments: lateral 1/3 of clavicles, acromion and spine of scapulae
Innervation: CN XI (motor), C3-4 (pain, proprioception)
Actions: descending fibres elevate scapulae, transverse fibres retract scapulae, ascending fibres depress scapulae, assists movement of neck when shoulders fixed
Attachments, innervation and actions of digastric
Origin: anterior belly from digastric fossa of mandible, posterior belly from mastoid notch on temporal bone
Insertion: intermediate tendon to body of hyoid
Innervation: anterior belly by nerve to mylohyoid, posterior belly by digastric branch of CN VII
Actions: elevates hyoid during swallowing and speaking
Attachments, innervation and actions of stylohyoid
Origin: styloid process of temporal bone
Insertion: body of hyoid
Innervation: stylohyoid branch of CN VII
Actions: elevates hyoid
Attachments, innervation and actions of mylohyoid
Origin: mylohyloid line on mandible
Insertion: mylohyoid raphe and body of hyoid
Innervation: nerve to mylohyoid (from inferior alveolar branch of CN V3)
Actions: elevates hyoid, floor of mouth and tongue whilst swallowing and speaking
Attachments, innervation and actions of geniohyoid
Origin: inferior mental spine of mandible
Insertion: body of hyoid
Innervation: C1 via CN XII
Actions: widens pharynx, shortens floor of mouth
Attachments, innervation and actions of omohyoid
Origin: superior scapula
Insertion: inferior hyoid
Innervation: C1-3 via ansa cervicalis
Actions: depresses hyoid
Attachments, innervation and actions of sternohyoid
Origin: manubrium, medial clavicle
Insertion: body of hyoid
Innervation: C1-3 via ansa cervicalis
Actions: depresses hyoid
Attachments, innervation and actions of sternothyroid
Origin: posterior manubrium
Insertion: oblique line of thyroid cartilage
Innervation: C2-3 via ansa cervicalis
Actions: depresses hyoid and larynx
Attachments, innervation and actions of thyrohyoid
Origin: oblique line of thyroid cartilage
Insertion: inferior hyoid
Innervation: C1 via CN XII
Actions: depresses hyoid and elevates larynx
What structure runs through the sternocleidomastoid?
CN XI runs through muscle
The sternocleidomastoid is crossed superficially by which three structures?
Crossed superficially by (from superior to inferior): great auricular nerve, external jugular vein, transverse cervical nerve
What structure lies deep to the upper half of the sternocleidomastoid?
Cervical plexus
What structure lies deep to the lower part of the sternocleidomastoid, overlying the anterior scalene?
Carotid sheath
What is the arterial blood supply of the sternocleidomastoid?
Occipital and superior thyroid arteries
What nerve innervates the sternocleidomastoid?
Spinal part of CN XI (C2-3)
What forms the borders of the lesser supraclavicular fossa?
Two heads of the sternocleidomastoid
What structure separates the neck into anterior and lateral regions?
Sternocleidomastoid
What are the four sub-triangles of the anterior triangle?
- Submandibular (digastric) triangle
- Submental triangle
- Carotid triangle
- Muscular (omotracheal) triangle
What forms the floor of the anterior triangle?
Pharynx
Larynx
Thyroid gland
What forms the roof of the anterior triangle?
Subcutaneous tissue including platysma
What forms the borders of the carotid triangle?
Superior: posterior belly of digastric, stylohyoid
Medial: superior belly of the omohyoid
Inferolateral: anterior border of the sternocleidomastoid
What are the seven contents of the carotid triangle?
- Carotid sheath and its contents:
- Common carotid artery (and bifurcation into internal and external carotids)
- Internal jugular vein
- CN X
- Cervical lymph nodes
- Sympathetic nerve fibres (carotid peri-arterial plexuses)
- Carotid sinus nerve) - CN XI
- CN XII
- Superior root of ansa cervicalis
- Thyroid gland
- Larynx
- Pharynx
What forms the apex of the anterior triangle?
Jugular notch
What forms the borders of the submental triangle?
Lateral: anterior belly of the digastric
Medial: midline
Inferior: hyoid bone
What forms the borders of the submandibular (digastric) triangle?
Superior: inferior border of the mandible
Medial: anterior belly of the digastric
Inferolateral: stylohyoid, posterior belly of the digastric
What forms the borders of the muscular (omotracheal) triangle?
Superior: hyoid, posterior belly of digastric
Medial: midline
Lateral: superior belly of omohyoid
Inferior: anterior border of sternocleidomastoid
What are the two contents of the submental triangle?
- Submental lymph nodes
- Small veins (unite to form anterior jugular)
What are the four contents of the muscular triangle?
- Sternohyoid
- Sternothyroid
- Thyroid gland
- Parathyroid glands
What are the five contents of the submandibular (digastric) triangle?
- Submandibular gland (takes up most of the triangle)
- Submandibular lymph nodes
- CN XII
- Mylohyoid nerve (branch of CN V3)
- Parts of facial artery and vein
What are the borders of the posterior triangle?
Anterior: posterior border of sternocleidomastoid
Posterior: anterior border of trapezius
Inferior: middle 1/3 of clavicle
Apex: superior nuchal line
What are the two sub-triangles of the posterior triangle?
- Occipital triangle
- Omoclavicular (subclavian) triangle
What forms the roof of the posterior triangle?
Investing layer of the cervical fascia
What forms the floor of the posterior triangle?
Prevertebral muscles:
- Splenius capitis
- Levator scapulae
- Middle scalene
- Posterior scalene
What structure separates the occipital and omoclavicular triangles?
Inferior belly of the omohyoid
What are the borders of the occipital triangle?
Anterosuperior: posterior border of sternocleidomastoid
Anteroinferior: inferior belly of omohyoid
Inferior: middle 1/3 of clavicle
Posterior: anterior border of trapezius
Apex: superior nuchal line
What are the seven contents of the occipital triangle?
- Part of external jugular vein
- Posterior branches of cervical plexus
- CN XI
- Trunks of brachial plexus
- Cervicodorsal trunk (transverse cervical artery)
- Superficial and deep cervical lymph nodes
- Occipital and superficial cervical arteries
What are the borders of omoclavicular (subclavian) triangle?
Posterior: inferior belly of omohyoid
Anterior: posterior border of sternocleidomastoid
Inferior: middle 1/3 of clavicle
What are the three contents of the omoclavicular (subclavian) artery?
- Third part of subclavian artery (+/- vein)
- Suprascapular artery and vein
- Supraclavicular lymph nodes
What are the two contents of the posterior cervical region?
- Trapezius
- Cutaneous branches of posterior rami of cervical spine nerves
What the five tributaries of the internal jugular vein? What vein is sometimes a sixth tributary?
- Sigmoid sinus
- Inferior petrosal sinus
- Facial and lingual veins
- Pharyngeal veins
- Superior and middle thyroid veins
(6. Occipital vein - usually drains to suboccipital venous plexus but may drain to internal jugular vein)
Describe the course of the external jugular vein
Descends in posterior triangle
Begins at angle of mandible from union of posterior division of retromandibular vein and posterior auricular vein
Crosses sternocleidomastoid obliquely
Pierces investing layer of deep cervical fascia at posterior border of sternocleidomastoid
Enters subclavian vein
Describe the surface anatomy of the internal, external, and anterior jugular veins
Internal: runs from earlobe to sternoclavicular joint
External: runs from earlobe to mid-point of clavicle
Anterior: runs from below chin under platysma
Where are the superior and inferior bulbs of the internal jugular?
Superior bulb after vein emerges from jugular foramen
Inferior bulb before vein enters the right subclavian
What landmarks correspond to the level of the carotid bifurcation?
Superior border of thyroid
Vertebral level C3/4
Describe the location of the carotid sinus and carotid bodies
Carotid sinus (baroreceptor): proximal part of internal carotid artery
Carotid bodies (chemoreceptor): lie between internal and external carotid arteries
What are the branches of the internal carotid in the neck?
No named branches in the neck
What part of the external cranium is not suppled by branches of the external carotid?
Orbit and part of the forehead and scalp supplied by supraorbital artery (branch of ophthalmic artery from the internal carotid artery)
Describe the course of the external carotid
Runs posteromedially between mandible and earlobe before being embedded in the parotid gland and terminating upon division into maxillary artery and superficial temporal artery
Name the branches of the external carotid, in ascending order
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1. Superior thyroid
2. Ascending pharyngeal
3. Lingual
4. Facial
5. Occipital
6. Posterior auricular
7. Superficial temporal
8. Maxillary
What are the anterior, medial, and posterior branches of the external carotid?
1 medial, 2 posterior and 3 anterior
Medial: ascending pharyngeal
Posterior: occipital, posterior auricular
Anterior: superior thyroid, lingual, facial
Describe the course of the superior thyroid artery. Which structures does it supply?
Runs deep to infrahyoid muscles and extends to thyroid
Supplies: superior thyroid, infrahyoid muscles, sternocleidomastoid, larynx via the superior laryngeal branch
Describe the course of the ascending pharyngeal artery. Which structures does it supply?
Ascends on pharynx medial (deep) to internal carotid
Supplies: pharynx, prevertebral muscles, middle ear, cranial meninges
Describe the course of the lingual artery. What structures does it supply?
Arches superoanteriorly, deep to CN XII and posterior belly of digastric
Supplies: tongue
Describe the course of the facial artery. What branches does it give off and what structures does it supply?
Gives off palatine and tonsillar branches, then passes superiorly under digastric and stylohyoid, and then angle of mandible, before giving off submental artery
Supplies: submandibular gland, floor of mouth via submental artery, most facial muscles
Describe the course of the occipital nerve. What structures does it supply?
Passes behind posterior belly of digastric in occipital groove of temporal bone, before terminating in many branches in the scalp
Supplies: posterior scalp
What structures are supplied by the posterior auricular artery?
Supplies: parotid gland, facial nerve, auricle, nearby scalp and muscles
How long is the thyroid?
5cm
Across what vertebral levels does thyroid extend? What tracheal ring does it extend to?
C5-T1
To 6th tracheal ring
Describe the arterial supply of the thyroid
Superior thyroid arteries supply superior poles
Inferior thyroid arteries supply inferior poles and all parathyroid glands
Many anastomoses between the arteries)
Describe the course of the superior thyroid artery
Arises from external carotid artery
Pierces pretracheal fascia
Divides into anterior and posterior branches
Describe the course of the inferior thyroid artery
Arises from thyrocervical trunks (off subclavian) with many branches
Why can hoarseness be a complication of thyroidectomy?
Recurrent laryngeal nerve (particularly on the right) is intimately related to thyroid and therefore at risk of injury during thyroidectomy
Describe the venous supply of the thyroid
Superior, middle and inferior thyroid veins from the thyroid venous plexus
Where do the superior, middle, and inferior thyroid veins drain?
Superior and middle drain to internal jugular vein
Inferior drains to brachiocephalic vein
