Neck anatomy Flashcards
What is the blood supply to the pharynx
Arterial supply to the pharynx is via branches of the external carotid artery:
* Ascending pharyngeal artery
* Branches of the facial artery
* Branches of the lingual and maxillary arteries.
Venous drainage is achieved by the pharyngeal venous plexus, which drains into the internal jugular vein.
What is the blood supply to the larynx
The arterial supply to the larynx is via the superior and inferior laryngeal arteries:
* Superior laryngeal artery – a branch of the superior thyroid artery (derived from the external carotid). It follows the internal branch of the superior laryngeal nerve into the larynx.
* Inferior laryngeal artery – a branch of the inferior thyroid artery (derived from the thyrocervical trunk). It follows the recurrent laryngeal nerve into the larynx.
Venous drainage is by the superior and inferior laryngeal veins. The superior laryngeal vein drains to the internal jugular vein via the superior thyroid, whereas the inferior laryngeal vein drains to the left brachiocephalic vein via the inferior thyroid vein.
Vocal cord histology
- Non-keratinised stratified squamous epithelium – Stratified layer provides extensive protection against foreign bodies which may accidentally enter the larynx.
- Reinke’s space – This watery, amorphous layer is rich in glycosaminoglycans. Due to its fluidity, the epithelium is able to vibrate freely above it to create sound.
- Vocal ligament – Lies at the free upper edge of the cricothryoid ligament.
- Vocalis muscle – Exceptionally fine muscle fibres that lie lateral to the vocal ligaments.
What is the vocal ligament a part of
Its the upper free edge of the conus elasticus
What are the contents of the pre-tracheal fascia
The trachea, the thyroid gland and the oesophagus lie in the pre-tracheal fascia
What muscles are contained in the pre-vertebral fasciA
Scalenes, levetor scapulae, splenu capitus
Describe the contents of the posterior triangle of the neck
Vessels: subclavian artery, transverse cervical artery , suprascapular artery and vein, occipital artery, external jugular vein
Nerves: CN11 and phrenic plus roots of the brachial plexus
Muscles: Omohyoid
Lymph nodes
What is the surface anatomy of the spinal accessory nerve
Posterior triangle of the neck, 1/3rd of the way down SCM to 1/3rd of the way up the anterior border of the trapezius
Describe how the anterior triangle can be further divided
How do you prevent recurrence of a thyroglossal cyst
Excise the middle one third of the hyoid bone as well
WHat is the sensory supply to the larynx
Superior laryngeal nerve above the level of the vocal cords and rec lar below
Where do the neck cartilages lie (What levels) and what arches are they derived from
C3 is hyoid, C4 is thyroid and C6 is cricoid
This helps us remember that the hyoid is 3rd arch derivative, thyroid is 4th and the cricoid is 5th
\What muscles abduct and adduct the vocal corts
posterior Cricoartenoids abduct and lateral adduct
Where do the superior and inf parathyroids originate
Sup is 4th pharyngeal pouch and the inf is 3rd
Which pharyngeal arch does the mylohyoid develop from
1st
How does the submandibular duct run
It lies deep to the mylohyoid and superficial to hyoglossus, it is 5cm long and opens on the floor of the mouth on either side of the lingual frenulum
How are the fascial layers of the neck divided
superficial and deep fascia
Superficial fascia
Lies deep to the dermis and surrounds the platysma and muscles of facial expression
Deep cervical fascia
Superficial layer: External investing layer
Middle: Pre-tracheal fascia and the carotid sheath
Internal layer: Prevertebral fascia
Investing fascial layer
Wraps around the submandibular gland, parotid, SCM, trap and muscles of mastication
What are the components of the pre-tracheal fascia
Muscular part: Encloses infrahyoid muscles
VIsceral: Thyroid and parathyroid
Buccopharyngeal fascia: Encompasses the pharynx and the oesophagus
Pre-vertebral fascia
Contains muscles and associated vertebrae
What is the retropharyngeal space and why is it important
Space between the pre-tracheal and the pre-vertebral fascia. Extends from the skull base and can hence increase spread of infection to and from the medastinum
The danger area is posterior to the retropharyngeal space and can get infected very quickly due to the presence of loose areolar tissue
Levels of lymph nodes
1a submental space
1b submandibular space
2a: superiorly there is the skull base, inferiorly there is the hyoid bone, laterally the anterior border of the SCM and medially the submandibular gland
2b: Sup and inf same as 2a but medially there is ant border of SCM and laterally post border of SCM. Seperated from 2a by the posterior border of the internal jugular vein
3: Hyoid to cricoid and basically on SCM, anterior border is the common carotid and posterior border is the posterior border of the SCM
4: cric to clavicle and on SCM and same borders as level 3
5a: posterior to scm and above cric
5b: 5a but below cric
6: pretracheal
7: sternal notch
What kind of neck dissections are there
Radical: Levels 1-5 and sacrificing the spinal accessory, IJV and the SCM
Modified: Preserving one or more of the above
Selective: One or more levels of lymph nodes removed and nothing sacrificed
Extended: Taking out structures that are not usually taken out in a neck dissection.
What are the contents of the occipital triangle of the neck
Transverse cervical artery, EJV, Spinal accessory, lymph nodes, upper trunk of the BP, cutaneous branches of the cervical plexus
What are the contents
Subclavian artery and vein, lymph nodes, SUprascapular arter, lower trunks of the brachial plexus, spex of the lung, phrenic nerve and thoracic duct.
How do patients with a carotid body tumour often present
Palpable neck lump and no other symptoms. They can also have a fever of unknown origin but this is uncommon.
Some can also present with hypotension, TIAs, signs of hypoglossal, rec lar, glossopharyngeal nerve palsy
What are the indications for a carotid endarterectomy
Name the anatomy of the cervical plexus
C1-C4
Located laterally to the transverse processes and emerge for the posterior triangle and emerge midway on the posterior border of the sternocleidomastoid
Anastomose with accessory and hypoglossal nerves and sympathetic
There is muscular and cutaneous components
Name the cutaneous branches of the cervical plexus
Lesser occipital (C2 only)
Greaterauricular (C2,C3)
Transverse cervical (C2,C3)
Supraclavicular (C3,C4)
Name the muscular branches of the cervical plexus
Ansa cervicalis (C1-C3): Infrahyoid strap muscles
Phrenic (C3-C5)
Communicating branches (C1) supplies genio and thyrohyoid
Segmental (C1-C4): Supplies ant and middle scalene
Name the supra and infrahyoid strap muscles of the neck
Erbs point
Halfway along the posterior border of the SCM at the level of the cricoid. Used for cervical nerve root blocks
Where are the superior and inferior thyroid glands normally found
The superior are the most consistent in position and are found at the inferior border of the cricoid cartilage, 1cm superior to the point of entry of the inferior thyroid arteries
Arise from the 4th pharyngeal arch
Inferior thyroid usually near the inferior pole >1cm below the inferior thyroid artery entry. 3rd pharyngeal arch origin
What is the pharynx
It is a fibromuscular tube extending from the base of the skull to the cricoid cartilage
What is the function of the pharyngeal muscles
The internal long muscles shorten the pharynx while speaking and swallowing
The external circular ones help in swallowing as well
Name the structures that pass between the middle and the inferior constrictors
Internal laryngeal nerve and superior laryngeal vessels
Name the structures that pass below the inferior constrictor
Inferior laryngeal vessels and rec lar
What is the blood supply to the pharynx
Ascending pharyngeal
Facial
inferior thyroid
Vertebral positioning of the larynx
C3 to C6
What are the cartilages of the larynx
Thyroid cricoid and epiglottic are unpaired
Paired: Arytenoid, cuneiform and corniculate
What is the blood supply to the larynx
Superior and inferior thyroid.
Describe the anatomy of the parotid gland
Superiorly: The zygomatic arch
Inferiorly: ramus of the mandible
Posteriorly: EAC and SCM + mastoid
Anteriorly: anterior border of the masseter
Where does the parotid duct lie
Opposite the upper second molar and pierces the buccinator muscle
What is the arterial and venous blood supply
Arterial: Branches of the external carotid artery and via superficial temporal and and posterior auricular
Venous: Retromandibular vein
Nerve supply of the parotid
Sensory: Auriculotemporal
Secretions: glossopharyngeal
What are the structures within the substance of the parotid gland
Superficial to deep
What is Freys syndrome
Auriculotemporal nerve misdirected regeneration and they wrongly join the sympathetic fibers which supply the sweat glands and vessels
Hence, this results in facial sweating while talking or thinking about food instead of salivation
What is the blood supply to the submandibular gland
lingual artery and submental branch of the facial artery
Why are stones more common in the submandibular gland as opposed to the parotid
Higher Ca concentration.
The Wartons duct is also longer and the saliva also has to flow against gravity
FACT
C2 vertebrae does not have a bifid spinous process and has dens
C1 has the superior articular facet to join the occipital condyles
Which joint permits flexion and extension of the neck
Atlanto-occipital joint, it is a synovial type joint surrounded by a loose capsule
Why is a fracture to the dens significant
Can severe the spinal cord and cause quadriplegia
What is a hangman’s fracture
Fracture of pars intercularis of C2 caused by hyperextension injury
FACT
The marginal mandibular nerve runs with the facial artery and is next to it as they both cross the mandible (The palpable area on the mandible).
What nerve runs close to the parotid duct
Buccal branch of the facial nerve
What are the landmarks of the cervical vertebrae
C1 = hard palate
C2 = angle of mandible
C3 = hyoid bone
C4 = superior thyroid notch
C5 = thyroidcatilage
C6 = cricoidcartilage
C7 = upper tracheal rings.
Name the structures
This is at the C4/C5 level as the carotids have not bifurcated yet and the vocal cords are just visible
Describe the larynx anatomy from this picture
The epiglottis is superior, arising from the anterior surface. The tracheal rings are inferior. The specimen shown is therefore viewed from the incised posterior side, i.e. we are looking at the front of the larynx from the inside.
A is the epiglottis
B aryepiglottic folds
C vallecula
D Piriform fossae
E Posterior cricoartenoid muscle
G is the vestibular fold - have a blood flow
H is the vocal fold - Do not have a blood flow
What nerve passes anterior to the external carotid artery
Hypoglossal nerve
What age do cranial sutures ossify
18-24 months
It is called craniosynostosis
By what age does the mastoid develop
2 years
What are the contents of the anterior triangle
What are the contents of the posterior triangle of the neck
What is the embryology of the thyroid gland
The thyroid gland develops from the foramen caecum (⅔ along the length of tongue from the tip) to pass forward and loop around beneath the hyoid bone. Incomplete descent → lingual or pyramidal thyroid Incomplete closure of the pathway of descent → thyroglossal cyst
What is the embryology of the parathyroid gland
Embryology? * Inferior parathyroid from the 3rd branchial arch with the thymus * Superior parathyroid from the 4th branchial arch
What is the muscle responsible for tensing the vocal cords
Muscles responsible for tensing vocal cords? By the 2 cricothyroid muscles
What veins are involved in oesophageal varicies
Left gastric vein and azygous vein
