anatomy of neck Flashcards
how can the neck be divided?
anterior and posterior triangles
what muscle separates the anterior and posterior triangles?
sternocleidomastoid
what is the posterior triangle of the neck bound by?
- Posterior border of the sternocleidomastoid (SCM)
- Anterior border of trapezius
- Middle 1/3 of the clavicle.
what are the important structures in the posterior triangle of the neck?
spinal accessory nerve external jugular nerve lymph nodes part of the subclavian artery Brachial plexus, cervical plexus, phrenic nerve
what does the spinal accessory nerve innervate?
SCM and trapezius
how can the prominence of the external jugular vein be used?
as an internal barometer
helps assess mean right atrial pressure - nearly identical to central venous pressure
where can EJV be seen?
above the clavicle for a short distance
what happens to the EJV when venous pressure is raised?
becomes more prominent
what causes the EJV to become more prominent?
increased intra-thoracic pressure, SVC obstruction, enlarged supraclavicular lymph nodes, heart failure, gym
what is mean right atrial pressure identical to?
central venous pressure
what fibres innervate SCM and trapezius?
somatic motor fibres
what spinal cord rootlets does the spinal accessory nerve form from?
C1-C5
describe the passage of the spinal accessory nerve?
ascends into the cranial cavity through the foramen magnum with the spinal cord
exits through the jugular foramen and becomes spinal accessory
what type of course does the spinal accessory nerve have?
subcutaneous
how can you injure the spinal accessory nerve?
lymph node surgery to the neck near SCM
what does spinal accessory nerve injury lead to?
atrophy of trapezius, drooping of shoulder, weakened shrugging shoulder
what spinal nerves does the cervical plexus arise from?
C1-C4
where do the cutaneous branches of the cervical plexus arise?
around the middle of the posterior border of the SCM
what are the 2 main branches of the cervical plexus?
phrenic nerve
ansa cervicalis
what are the roots of the phrenic nerve?
C3 and C4 and they pick up additional C5 roots
where does the phrenic nerve descend?
obliquely with IJV across anterior scalene.
where does the ansa cervicalis run?
motor loop to infrahyoid muscles
what are the borders of the anterior triangle of the neck?
- Midline of neck from chin to jugular notch.
- Anterior border of SCM
- Lower border of mandible and beyond to mastoid process.
name the subdivisions of the anterior triangle
- submandibular (digastric)
- carotid
- muscular
- submental
what is in the submandibular triangle?
submandibular glands fill most of the triangle, hypoglossal nerve, parts of the facial artery and vein
what is found in the muscular triangle?
Sternohyoid, thyrohyoid and sternothyroid (infrahyoid muscles). Thyroid and parathyroid glands.
what is found in the submental triangle?
floor of the mouth –> mylohyoid
what is the carotid triangle bound by?
- Posterior belly of digastric
- Superior belly of Omohyoid (one of the infrahyoid muscles)
- Anterior border of SCM
why is the carotid highly vascular?
common carotid artery
internal jugular vein
what are the contents of the carotid triangle
common carotid carotid bifurcation --> external and internal carotid arteries carotid sinus carotid body internal carotid Glossopharyngeal, vagus, Spinal accessory, Hypoglossal Cervical sympathetic trunk Ansa cervicalis
what does the carotid sinus detect? what type of receptor is it?
blood pressure (baroreceptor)
what does the carotid body detect? what type of receptor is it?
measure O2 and CO2 content of the blood
chemoreceptor
what are the branches of the external carotid?
- Superior thyroid artery
- Ascending pharyngeal
- Lingual
- Facial
- Occipital
- Posterior auricular
- Maxillary – middle meningeal branch supplies the dura and the periosteum in the skull
- Superficial Temporal
what structures does the external carotid supply?
face, tongue, mouth, upper jaw, eye, scalp and the inside of the skull and the dura
what does the carotid sheath contain?
• Common carotid artery, Internal carotid artery, Internal jugular vein
• Vagus nerve
• Ansa cervicalis over IJV
• Ascending sympathetic fibres use internal carotid artery for support
• Lymph nodes
- cervical parts of the sympathetic trunk
what are the 3 cervical ganglia?
superior
middle
inferior
how do the cervical ganglia get their presynaptic fibres?
via superior thoracic nerves
where do the cervical ganglia send post ganglionic fibres?
cervical spinal nerves
thoracic viscera
head and neck viscera
what causes horner’s syndrome?
lesions to the sympathetic trunk in the neck or descending fibres in the brainstem
what are the symptoms of horner’s syndrome?
o Contraction of pupil (miosis)
o Drooping of superior eyelid (paralysis of smooth muscle in levator palpebrae superioris)
o Sinking of eye (enophtalmos)
o Vasodilation, absence of sweating
what can damage/compression of the vagus during surgery cause and why?
alteration in voice bc these nerves supply laryngeal muscles
which IJV is used in IJV puncture and why?
right IJV used: straighter course with brachiocephalic vein into SVC. Thoracic duct (main lymph trunk) drains at venous angle on the left
when does IJV pulse rise?
conditions such as mitral valve disease, increased pressure in pulmonary circulation
what does the suprahyoid muscles do?
make up the floor of the mouth
provide base for tongue and elevate hyoid and larynx to allow for swallowing and the production of tone (include mylohyoid, digastric, stylohyoid
what do the infrahyoid muscles do?
depress hyoid and larynx during swallowing and speaking (Sternohyoid, thyroid hyoid, sternothyroid, Omohyoid).
what do the extrinsic larynx muscles do?
move larynx as a whole - supra and infrahyoid muscles
what do the intrinsic muscles of the larynx do?
move components of the larynx: alter length and tension of vocal folds and size and shape of rima glottides and therefore the size and volume of speech
what nerves innervate the different parts of the larynx?
o Cricothyroid - superior laryngeal N (CN X)
o All others - recurrent laryngeal N (CN X)
what is the rima glottidis?
the gap between vocal folds
what happens to the throat muscles during normal respiration?
laryngeal muscles relaxed: the rima glottides is a narrow slit
what happens to the throat muscles during deep respiration?
Vocal ligaments abducted by contraction of posterior cricoarytenoid muscles (rima glottides opens widely)
what happens to the throat muscles during phonation?
arytenoid muscles adduct arytenoid cartilages, cricoarytenoid adduct vocal ligaments. Air forced between vocal ligaments: sound.
what happens to the throat muscles during whispering?
vocal ligaments strongly adduct, relaxed arytenoids
what does the vagus branch into?
superior laryngeal nerve and recurrent laryngeal nerve
what are the branches of the superior laryngeal nerve and what do they innervate?
- Internal – sensory and autonomic to larynx above vocal cords
- External – motor to criciothyroid
what does the recurrent laryngeal nerve innervate?
o Motor to all other intrinsic muscles of the larynx
o Sensory to area below vocal folds
how can a superior laryngeal nerve lesion occur?
during thyroidectomy or through compression
o Goitre
what does paralysis of superior laryngeal nerve lead to?
• Anaesthesia of superior laryngeal mucosa
o Cough reflex (an important protective mechanism)
• A monotonous voice - Paralysed cricothyroid (unable to vary length and tension – but may go unnoticed)
what does paralysis of the recurrent laryngeal lead to?
Recurrent laryngeal
• Paralysed vocal folds
• Hoarseness/dysphonia
