The neck Flashcards
What are the different layers of the neck ?
Fascia;
- Superficial (subcutaneous tissue)
- Investing
- Pretracheal (With Buccopharyngeal fascia)
- Carotid Sheath
- Prevertebral fascia
Structures are compartmentalised by layers of fascia - Compartments;
- Visceral
- x2 Vascular
- Vertebral
Superficial fascia - Is subcutaneous tissue - continuous with superficial fascia of thorax, connects with mandible + facia muscles, has cutaneous nerves and muscles, lymph nodes and 1 muscle - platysma
Investing splits into layers and encloses certain structures like sternocleidomastoid, infrahyoid, trapezium, submandibular etc… pierced by external and anterior jugular veins + cervical plexus
What makes up the Pretracheal space?
Pretracheal space - Between investing layer & pretracheal fascia; area extends between neck & superior mediastinum
What makes up the True’ retorpharyngeal space?
‘True’ retorpharyngeal space - Between buccopharyngeal fascia & superficial preverteebral fascia (alar fascia); area extends between base of skull and superior mediastinum
Infections from the pharynx can spread via this layer into the posterior mediastinum
What makes up the Danger (alar) space/fascial space?
Danger (alar) space/fascial space within prevertebral layer - Within prevrtebral layer (alar fascia & dip prevrtebrsal layer); covers anterior surface of transverse processes & bodies of cervical vertebrae; area extends from case of skull through posterior mediastinum to diaphragm
In healthy individuals, this layer is indistinguishable from the ‘true’ retropharyngeal space
Infections from the pharynx can spread via this layer into the posterior mediastinum
Fluid collections & abscesses in this space are visible in radiological investigations
What are the borders of the Anterior Triangle ?
Anterior triangle boundaries;
- Inferior border of mandible
- Anterior border of sternocleidomastoid
- Midline of neck
Roof;
- Deep investing fascia around muscles
Floor;
- Pretracheal fascia
- Carotid sheath (postreolaterally)
Leads to thoracic inlet
(Can be further split into smaller triangles)
What smaller triangles can the neck be split up into and their boundaries?
Submandibular (digastric) triangle;
- Anterior and posterior bellies digastric
- Body of mandible
Submental triangle;
- Anterior belly of digastric
- Hyoid
- Midline
Carotid triangle;
- Posterior belly of digastric
- Superior belly of Omohyoid
- Sternocleidomastoid
Muscular (omotracheal) triangle;
- Superior belly of Omohyoid
- Sternohyoid
- Sternocleidomastoid
(Remember triangles by Site of SCM / SSCM)
What can you find inside the Submandibular triangle ?
Submandibular triangle contents;
- Submandibular gland
- Submandibular lymph nodes
- Facial artery (pulse) and vein
- Some of CN XII
What can you find inside the Submental triangle ?
Submental triangle contents;
- Submental lymph nodes
What can you find inside the Carotid triangle ?
Carotid triangle contents;
- Thyroid gland
- Larynx
- Pharynx
- Carotid sheath (and its contents)
- Branches of cervical plexus
- Ansa cervicalis
- Deep cervical lymph nodes
- Parts of CN XI and XII
What can you find inside the Muscular / Omotracheal triangle?
Muscular / Omotracheal triangle content;
- Sternohyoid muscles
- Sternothyroid muscles
- Thyroid gland
- Parathyroid glands
What are the features of the Digastric muscle ?
2 Bellies (hence “diagastric”)
Anterior belly;
- originates at digastric fossa on lower medial aspect of mandible
- Innervated by nerve to mylohyoid - CN V3 (1st pharyngeal arch)
Posterior belly;
- Originates at mastoid notch on medial side of mastoid process
- Innervated by nerve to digastric branch - CN VII (2nd pharyngeal)
Both bellies insert at attachment of their intermediate tendon at hyoid
Actions;
- Anterior belly raises hyoid & opens mouth by lowering mandible
- Posterior belly elevates & reacts hyoid bones
What are the muscles of the hyoid bone ?
Suprahyoid muscles;
- Above hyoid
- Connect to skull or mandible
Infrahyoid muscles;
- Below hyoid
- Connect to inferior structures (sternum, scapula, thyroid cartilage)
Doesn’t articulate with any other bone, suspended by muscles, keep hyoid in place
Connected to larynx and pharynx
What are the Suprahyoid muscles and their function?
Suprahyoid muscles;
- Mylohyoid
- Digastric
- Stylohyoid
- Geniohyoid
Raise hyoid - swallowing
What are the Infrahyoid muscles and their function?
Infrahyoid (strap) muscles;
- Sternohyoid
- Omohyoid
- Thyrohyoid
- Sternothyroid
Depresses the hyoid and pulls hyoid back into position
Innervation;
- Sternohyoid, Omohyoid and Sternothyroid by anterior rami of C1 - C3
- Thyrohyoid by C1, hitchhiking CN-XII
What are the functions of the thyroid gland?
Thyroid gland;
- Endocrine gland
- Required for metabolism and growth / development
- Thyroid hormones; T3 & T4
- Calcitonin (Lowers blood calcium level)
T4 - thyroxine - longer action, T3 more potent, can be converted into each other
Where is the thyroid gland located and what is it made of ?
Thyroid gland location;
- Within visceral compartment of neck
- Composed of 2 lateral lobes (right & left) (extends from thyroid cartilage to 5th tracheal ring)
- Midline isthmus (level of 3rd tracheal ring)
- Midline pyramidal lobe (variably present, remnant of thyroglossal duct)
What is the arterial and venous supply of the Thyroid gland?
Arterial supply;
- Superior thyroid artery (1st branch of external carotid artery)
- Inferior thyroid artery (branch of thyrocervical trunk from subclavian)
Venous drainage (thyroid venous plexus);
- Superior thyroid vein (into internal jugular vein)
- Middle thyroid vein (into internal jugular vein)
- Inferior thyroid vein (into brachiocephalic vein)
All endocrine organs need lots of blood to secrete into
What are the features of the Parathyroid gland?
Parathyroid;
- Two pairs (superior & inferior) of small glands usually on posterior surface of thyroid by fact position varies
Arterial supply;
- Inferior thyroid arteries (branch of thyrocervical trunk from subclavian) supply parathyroid glands
Venous drainage;
- The same as thyroid
Venous drainage (thyroid venous plexus);
- Superior thyroid vein (into internal jugular vein)
- Middle thyroid vein (into internal jugular vein)
- Inferior thyroid vein (into brachiocephalic vein)
Innervation;
- Both thyroid and parathyroid are innvervated by the thyroid branches from the cervical sympathetic ganglia
Function;
- Regulate calcium and phosphorus
- Calcium only ion with its own organ - parathyroid, reservoir from bones osteoclasts
Note: The recurrent laryngeal nerve is located close to the thyroid and parathyroid glands - makes for a surgical challenge !
What are thee boundaries of the Posterior Triangle ?
Bounded by;
- Posterior border of SCM
- Anterior border of trapezius
- Middle 3rd of clavicle
- Occipital bone
Roof;
- Deep investing fascia
- SCM and trapezius
Floor;
- Prevertebral fascia
- Splenius capitis, levator scapulae and scalene muscles
Disagreement on anterior border as 2 heads of SCM, some say sternal head some say clavicular head
What are the contents of the Retromandibular Fossa?
Retromandibular Fossa contents;
- Parotid gland
- Styloglossus, Stylohyoid, Stylopharngeal muscles
- Stylomandibular and Stylohyoid ligaments
- Retromandibular vein, maxillary and superficial temporal vessels
What are the branches and muscular and cutaneous branches of the cervical plexus?
Cervical Plexus;
- Formed by the anterior rami of C1 - C4, deep to sternocleidomastoid
Muscular branches;
- Phrenic nerve (C3-5) to the diaphragm (“3,4,5 Keep diaphragm alive!”)
- Ansa cervicalis (C1-3) to infrahyoid muscles
What Cutaneous branches are formed and where ?
Cutaneous branches are formed superficial at Erb’s point!
- Lesser occipital nerve (C2)
- Greater auricular nerve (C2-3)
- Transverse cervical nerve (C2-3)
- Supraclavicular nevre (C3-4)
Where do Common carotids come from and where do they go to ?
Common carotids are branches of the aortic arch on the left, brachiocephalic trunk on the right
Bifurcates to internal and external carotid arteries at C3/4 vertebral level or upper margin of thyroid cartilage
Internal carotid artery has no branches in the neck
What are the features of the Carotid Sinus?
Carotid Sinus;
- Enlargement / dilation at bifurcation of common carotid artery or beginning of internal carotid artery
- Contains baroreceptors
- Monitors blood pressure
- Helps keep blood pressure within homeostatic values
Innervated by CN IX;
- Nucleus of tracts solitarius
- To the cardioregulatory & vasomotor centres in the medulla (vital centres…)
- To dorsal nucelus of vagus
What are the features of the Carotid Body?
Carotid Body;
- Small organ (2-5mm) which houses chemoreceptors located at bifurcation of common carotid artery
- Monitors blood O2, CO2, & pH (& temperature)
- Responds in emergency situations by increasing respiration, blood pressure & cardiac rate (not as much at rest)
Innervated by CN IX;
- Nucleus of tracts solitarius
- To the cardioregulatory & vasomotor centres in the medulla (vital centres…)
What are the Superficial Veins of the neck and their features ?
Superficial veins;
- Internal jugular vein
- Anterior jugular vein
- External jugular vein
- Jugular venous arch
What are the features of the Internal jugular vein ?
Internal jugular vein;
- Continuation of sigmoid sinus
- Exits skull via the jugular foramen
- Enters carotid sheath and runs lateral to common carotid artery
- Joins subclavian vein to become brachiocephalic vein
What are the features of the External jugular vein ?
External jugular vein;
- Begins at angle of mandible, joining retromandibular & posterior auricular veins
- Crosses over SCM
- Pierces investing fascia to enter & drain into subclavian vein
What are the features of the Anterior jugular vein ?
Anterior jugular vein;
- Arises near the hyoid bone & run on either side of the midline
- Drains into the external jugular vein
What are the features of the Jugular venous arch ?
The jugular venous arch is usually formed by the two anterior jugular veins, just above the sternum, which travels downward along the midline between the pretracheal and superficial layers of the cervical fascia, i.e., in the space of Burns. The jugular venous arch either drains into the subclavian or the EJV.
- Isn’t described in slides just for context, mainly know location”
What are the lymph nodes of the neck?
Lymph nodes of the neck;
- Preauricular
- Posterior auricular
- Occipital
- Submental
- Submandibular
- Jugulodigastric
- Superficial cervical
- Deep cervical chain
- Posterior cervical
- Supradavicular
What resource would you use when suspecting infection of lymph nodes or a lesion along them?
Keep in mind when suspecting infection or lesion that it may spread along lymphatics and you would bring up image attached and look where it drains
Don’t memorise image!
Where are the lymph nodes of the scalp and face?
- No lymph nodes in scalp or face
- Except parotid / buccal region
Don’t forget supraclavicular - stomach cancers can metastasize to here
What fascial spaces is there and what is there relevance ?
Fascial spaces (Potential spaces!);
- Pretracheal space
- ‘True’ retorpharyngeal space
- Danger (alar) space/fascial space within prevertebral layer
Infection / fluid / gas / tumours can easily spread within each compartment or within the spaces since enclosed with or bounded by fascia
The thoracic structures are at risk since many compartments & spaces extend into the thorax
