Anatomy of the Neck Flashcards
What are the boundaries of the posterior triangle in the neck?
Medial oblique border = SCM
Lateral border = trapezius
Inferior border = middle third of clavicle
Why may the external jugular vein be more prominent than usual?
EJV functions as an internal barometer (pressure monitor), so raised venous pressure causes increased EJV prominence but heart failure, SVC obstruction, enlarged supraclavicular lymph nodes, raised intra-thoracic pressure are all causes
Describe the contents of the posterior triangle in the neck
Internal jugular vein, external jugular vein, spinal accessory nerve
How may the spinal accessory nerve be damaged?
It has a subcutaneous course and therefore it may be injured in lymph node surgery
What does the spinal accessory nerve innervate in the neck?
SCM and trapezius
Describe the path of the spinal accessory nerve
Arises as rootless from sides of the spinal cord and ascends into the cranial cavity via foramen magnum and exits through the jugular foramen
Which nerve roots contribute to the cervical plexus?
C1-4
Where do the cutaneous branches of the cervical plexus emerge?
Around the middle of the posterior border of the sternocleidomastoid muscles
What nerve roots supply the ansa cervicalis?
C1-C3
Describe the passage of the phrenic nerve
C3 and C4 pick up additional C5 roots and then descend down obliquely with the internal jugular vein, across the anterior scalene muscle and into the thorax
Which plexus provides the motor supply to the infrahyoid muscles?
Cervical plexus
What are the borders of the anterior triangle in the neck?
Lateral border = SCM muscle
Medial oblique border = midline of neck from chin to jugular notch
Superior border = Lower border of mandible to mastoid process
Name the four further subdivisions of the anterior triangle in the neck
Submandibular, sub-mental, carotid and muscular
Describe the submandibular subdivision of the anterior triangle in the neck
Submandibular gland fills most of this triangle as well as the hypoglossal nerve and parts of facial artery and vein
Describe the carotid subdivision of the anterior triangle in the neck
Highly vascular (common carotid and IJV), contains CN IX, X, XI, XII cervical sympathetic trunk and ansa cervicalis
Describe the muscular subdivision of the anterior triangle in the neck
Sternohyoid, sternothyroid, thyrohyoid and omohyoid muscles (infrahyoid muscles). This also contains the thyroid and parathyroid glands.
Describe the sub-mental subdivision of the anterior triangle in the neck
Contains the floor of the mouth (mylohyoid)
What is the difference between the internal and external carotid arteries?
Internal carotid has no branches until it enters the skull whereas the external carotid has many branches
Describe the borders of the carotid subdivision of the anterior triangle in the neck
Posterior belly of the digastric muscle, superior belly of the omohyoid muscle and by the anterior border of the SCM
Where is the common carotid artery palpated?
Anterior border of the SCM at the level of the thyroid cartilage; if palpable, this suggests a systolic pressure of at least 40mmHg
What are the contents of the carotid sheath?
Contains the common carotid artery, internal carotid, IJV, CN X (vagus) ansa cervicalis and lymph nodes
Which nerves supply presynaptic fibres to the cervical parts of the sympathetic trunk?
Superior thoracic nerves
What do the sympathetic cervical ganglia send fibres to?
Cervical spinal nerves, thoracic viscera, head and neck viscera
How do sympathetic nerve fibres travel back up into the brain?
Hitch a lift on the internal jugular vein
What are the symptoms of Horners syndrome?
Pupil constriction, drooping of eyelid (due to paralysis of smooth muscle in lavatory palpebrae superioris, sinking of the eye, vasodilation and absence of sweating
What is the cause of Horners syndrome?
Damage to the sympathetic trunk in the neck
When may surgical dissection of the carotid triangle be required?
To reach the carotid system of arteries, IJV, vagus, hypoglossal nerves or the cervical sympathetic trunk
What is IJV puncture?
The right IJV is a straight course and can be used with the brachiocephalic vein to enter the superior vena cava
What causes the JVP?
Pulsations of internal jugular vein; provide information about the heart, specifically right atrial pressure as there are no valves in the brachiocephalic vein or SVC, the blood can travel up the vein when at 45 degrees
What may cause a rise in JVP?
Mitral valve disease, increased pressure in pulmonary circulation or conditions of the right side of the heart
What muscles are in the anterior cervical region?
Suprahyoid and infrahyoid
What is the suprahyoid muscle?
Constitutes the floor of the mouth to form a base for the tongue and elevates the hyoid and larynx –> swallowing and tone production
What is the infrahyoid muscle?
Depress the hyoid and larynx during swallowing and speaking
What is the difference in action of the suprahyoid and the infrahyoid muscles?
Suprahyoid elevates hyoid and larynx whereas infrahyoid depresses hyoid and larynx
What are the three constrictor muscles of the pharynx?
Superior, middle and inferior pharyngeal constrictors
What are the longitudinal muscles of the pharynx?
Palatopharyngeus, salpingopharyngeus, stylopharyngeus - these are involved with elevating the pharynx during swallowing
What is the main innervation to the pharynx?
Vagus (CN X)
What are the extrinsic muscles of the larynx?
Supra and infrahyoid muscles
What is the function of the intrinsic muscles of the larynx?
These move the laryngeal components and alter the length and tension of the vocal folds and size and shape of the rima glottidis changes
What is the rima glottidis?
Aperture between the vocal folds
How is the rima glottidis affected by normal respiration?
Laryngeal muscles relax (ligaments are relaxed) so rima glottidis becomes a narrow slit
How is the rima glottidis affected by deep respiration
Vocal ligaments are abducted by the contraction of the posterior cricoarytenoid muscle –> rima glottidis opens widely
How is sound produced in phonation?
Air is forced through the vocal ligaments to make sound
What is the function of the posterior cricoarytenoid muscle?
The only muscles to open the vocal cords. By rotating the arytenoid cartilages laterally, these muscles abduct the vocal cords and thereby open the rima glottidis
What is the function of the lateral cricoarytenoid muscle?
Adduct and medially rotate the cartilage, pulling the vocal ligaments towards the midline and backwards and so closing off the rima glottidis
What is the innervation to the intrinsic (arytenoid) laryngeal muscles?
All the cricothyroid) are innervated by the inferior laryngeal nerve – the terminal branch of the recurrent laryngeal nerve, itself a branch of the vagus nerve. The cricothyroid is innervated by the external branch of the superior laryngeal nerve – again derived from the vagus nerve.
How is the rima glottidis affected in phonation?
Arytenoid muscles adduct the arytenoid cartilages and simultaneously the lateral cricoarytenoids moderately adduct the vocal ligaments –> air is forced between the vocal ligaments in order to produce sound
How is the rima glottidis affected in whispering?
Vocal ligaments are strongly adducted (by lateral cricoarytenoids) but the arytenoids are relaxed so air is forced through a larger gap in order to produce a softer sound
Outline the three phases of deglutition (swallowing)
1) Voluntary phase - movement of food from mouth –> oropharynx, bolus pressed against palate and pushed towards oropharynx by tongue muscles
2) Involuntary and rapid phase - swallowing initiated by food touching oropharynx –> pharynx widens and shortens to receive bolus –> suprahyoid muscles contract –> nasopharynx closes and epiglottis closes off larynx
3) Involuntary phase - sequential contraction of three pharyngeal constrictor muscles
