Head and Neck Flashcards
What structures does cranial nerve VII innervate?
Cranial nerve VII is the facial nerve, it innervates the facial muscles, buccinators, superficial muscles of the neck and chin, muscles of the ear and occipitofrontalis muscle
State the anatomical location of the neck
Between the lower margin of the mandible, suprasternal notch of the manubrium and the upper border of the clavicle
What are the layers of the neck?
Skin, subcutaneous fat, platysma muscle, deep cervical fascia, pre tracheal fascia, carotid sheaths and the pre-vertebral fascia
What is the significance of the retropharyngeal space?
Located behind the pharynx and it runs to the diaphragm. If infected it could spread and cause mediastinitis
What is the significance of the parapharyngeal space?
Contains the carotid sheaths and lies parallel to the pharynx. Infections can spread to about T2/3 and can cause tonsillitis or dental problems
State the suprahyoid and infrahyoid muscles
Suprahyoid - digastric, mylohyoid, stylohyoid and geniohyoid
Infrahyoid - thyrohyoid, sternohyoid, sternothyroid, omohyoid
What are the main contents of the anterior triangle?
IJV, facial vein, retromandibular vein and EJV. Submandibular gland. Nerve to mylohyoid. Anterior JV, hyoid bone, oesophagus, thyroid and parathyroidg glands. Larynx. Carotid sheath and branches of the external carotid artery. Lymph nodes. Ansa cervicalis.
What forms the internal jugular vein?
Anastomosis of the sigmoid sinus of the dura mater and the common facial vein - provides venous drainage of the skull
Which vessels form the external jugular vein?
Posterior division of the retromandibular vein and the posterior auricular vein
State the borders of the anterior triangle of the neck
Superiorly - inferior border of the mandible
Laterally - medial border of SCM
Medially - imaginary sagittal line down the midline of the body
State the borders of the posterior triangle of the neck
Anteriorly - posterior border of the SCM
Posteriorly - anterior border of the trapezius
Inferiorly - middle third of the clavicle
What does the superficial cervical fascia encompass?
Investing layer (trapezius, SCM, parotid and submandibular glands), pre-tracheal layer (infrahyoid muscles, thyroid gland, trachea and oesophagus), prevertebral layer (vertebral column and associated muscles) and the carotid sheath (common carotid artery, internal jugular vein, vagus nerve and lymph nodes).
What is the most common cause of non-traumatic facial paralysis?
Inflammation of the facial nerve near its exit from the cranium at the sylomastoid foramen. This leads to oedema and compression of the nerve in the intracranial facial canal (Bell’s palsy)
What are the structural features present at 4 weeks in regards to the head and neck in an embryo?
An association with the brain, sensory placodes and the involvement of other systems e.g. brain and CVS
Describe pharyngeal arches
A system of mesenchymal proliferations in the neck region of an embryo. There are 5 in total (1-4 and 6). Each arch has an associated artery, nerve and cartilage bar and is lined by endodermal tissue.
What are the three vesicles in the three vesicle stage called?
Prosencephalon, mesencephalon and rhomboencephalon
Explain why the distribution of the cranial nerves is the way it is
Initially they start off segmental (like the other nerves) however their segmental arrangement is lost as the foetus grows.
What are the muscle derivatives of the first pharyngeal arch?
Muscles of mastication, mylohyoid, anterior belly of digastric muscle, tensor palati and tensor tympani
What are the muscle derivatives of the second pharyngeal arch?
Muscles of facial expression, occipitofrontalis, platysma, stylohyoid, posterior belly of the digastric muscle, stapedius and auricular muscles
What are the muscle derivatives of the third pharyngeal arch?
Stylopharyngeus
What are the muscle derivatives of the fourth pharyngeal arch?
Cricothyroid, levator palatini and constrictors of the pharynx
What are the muscle derivatives of the sixth pharyngeal arch?
Intrinsic muscles of the larynx
Describe cranial nerve V
CN V (aka trigeminal nerve) is the nerve of the first arch. Principle sensory nerve of the head - skin of face and lining of mouth/nose. Motor - muscles of mastication and muscles derived from the mandibular process
Describe cranial nerve VII
CN VII (aka facial nerve) is the nerve of the second pharyngeal arch. Passes through the stylomastoid foramen and the oarotid gland. Mostly supplies motor innervation - muscles of mastication and other muscles derived from the second arch. Small sensory component - anterior 2/3 of taste buds in the tongue
Describe cranial nerve IX
CN IX (aka glossopharyngeal nerve) is the nerve of the third arch. Innervates the stylopharyngeus and provides sensory innervation to posterior 1/3 of the tongue
Describe cranial nerve X
CN X (aka vagus nerve) is the nerve of the fourth and sixth arches. Fourth arch branch is the superior laryngeal nerve which supplies the cricothyroid and constrictors of the pharynx. Sixth arch branch is the recurrent laryngeal nerve which supplies the intrinsic muscles of the larynx
State the neural crest derived cartilage bar for each of the pharyngeal arches
First - Meckel’s, second - reichert’s, fourth and sixth - cartilages of the larynx
What are the arterial contributions of the pharyngeal arches?
First - maxillary artery and external carotid, second - stapedial artery and hyoid artery, third - common carotid and internal carotid arteries, fourth - right gives subclavian artery and left gives aortic arch and sixth - right gives pulmonary artery and left gives pulmonary artery and ductus arteriosus.
How are the parathyroid glands formed?
The third and fourth pharyngeal pouches divide into dorsal and ventral components and go on to form the parathyroid glands.
How is the thymus formed?
The ventral part of the third arch forms the thymus (starts off as two separate lobes that then migrate and form a single gland)
What is the fate of the second pharyngeal pouch?
The epithelia proliferates and is then colonised by lymph precurors
Describe the development of the middle ear
Ossicles are formed from first and second pharyngeal arch cartilages (Meckel’s = malleus and incus, Reichert’s = stapes). First pharyngeal pouch endoderm forms the auditory tube that enlarges to incorporate the tympanic cavity surrounding the ossicles. Mesoderm comes from the first and second arch.
What are the muscles of the face?
Orbital, nasal and oral muscles
Explain why the left common carotid artery is longer than the right common carotid artery
The RCC branches off the subclavian artery whereas the LCC branches directly off the arch of the aorta and thus has a longer way to travel to get to the head
Where do the carotids terminate?
Midway between the angle of the mandible and the mastoid process of the temporal bone
Where is the ‘common carotid line’?
A line beginning below the sternoclavicular joint and terminating midway between the angle of the mandible and the mastoid process
At what level do the common carotid arteries bifurcate?
Level of the superior border of the thyroid cartilage
What are the branches of the external carotid artery in the neck?
Superior thyroid artery, ascending pharyngeal artery, lingual artery, facial artery, occipital artery, posterior auricular artery, maxillary artery and the superficial temporal artery
Which arteries does the subclavian artery give rise to?
Vertebral arteries, internal thoracic artery and the thyrocervical arteries
Where does the external carotid artery split into the maxillary and the superficial and temporal arteries?
In the substance of the parotid gland, accompanied by the facial nerve and the retromandibular vein
State the boundaries of the carotid triangle
Superior - posterior belly of the digastric muscle
Lateral - SCM
Medial - superior belly of omohyoid
What does the carotid triangle contain?
Carotid arteries, internal jugular vein, vagus nerve and hypoglossal nerve
What are the arteries that supply the scalp?
Supra-orbital, supratrochlear, superficial temporal, posterior auricular and occipital arteries
State the layers of the scalp
Skin, connective tissue, aponeurosis, loose connective tissue and the periosteum