Neck Triangles Flashcards
Hyoid bone
U shaped bone
Located at C3 level in the anterior neck
Doesn’t articulate with any skeletal elevenths so is suspended by muscles and ligaments
Anterior triangle boundaries
Superiorly: inferior border of mandible
Laterally: anterior border of SCM
Medially: sagittal line down midline of neck
Roof: deep investing fascia
Floor: pretracheal fascia
Anterior triangle subdivision
Submandibular triangle
- contains submandibular gland, lymph nodes, parts of CN XII, mylohyoid nerve and parts of facial artery and vein
Submental triangle
- contains submental lymph nodes and some small veins
Carotid triangle
- contains thyroid gland, pharynx, carotid sheath, branches of cervical plexus, superior root of ansa cervicalis, parts of CN XI, CN XII
Muscular triangle
- contains sternohyoid, sternothyroid muscles, thyroid and parathyroid glands
Suprahyoid muscles
Raise the hyoid bone as required during swallowing
Mylohyoid
Digastric
Geniohyoid
Stylohyoid
Mylohyoid
Action: elevates the hyoid bone and forms floor of oral cavity
Originates: mylohyoid line on mandible
Inserts: into body of hyoid and fibres of opposite Mylohyoid
Digastric
Anterior belly: originates at Digastric fossa on lower medial aspect of mandible. Action: raises hyoid and opens mouth by lowering mandible
Innervation: nerve to Mylohyoid
Posterior belly: mastoid notch on medial side of mastoid process
Action: elevates and retracts hyoid bone.
Innervation: Digastric branch of CNVII facial
Both insert at their intermediate tendon
Stylohyoid
Originates at the styloid process
Inserts into body of hyoid (laterally)
Action: pulls hyoid bone upwards posterosuperiorly
Innervation: CN VII
Geniohyoid
Located superior to Mylohyoid
Originates: from the mandible
Inserts: at body of hyoid
Action: fixed mandible (elevates and pulls hyoid foward) , fixed hyoid (pulls mandible downward and inward)
Innervation: via anterior ramus of C1 (travels with CN XII)
Infrahyoid (strap) muscles
Depress or fix hyoid bone and provide attachment for suprahyoid muscles
Sternohyoid
Sternothyroid
Thyrohyoid
Omohyoid
Sternohyoid
Originates at posterior surface of sternoclavicular joint and manubrium
Inserts into body of hyoid medially
Action: depresses hyoid after elevation during swallowing
Anterior rami of C1 to C3 though ansa cervicalis
Omohyoid
Inferior and superior bellies
Superior belly: originates at its intermediate tendon and inserts into body of hyoid laterally
Inferior belly: originates at superior border of scapula and inserts at its intermediate tendon in posterior triangle
Action: depresses and fixes the hyoid bone
Innervated by anterior rami of C1-3 through ansa cervicalis
Sternothyroid
Originates at posterior surface of manubrium and inserts into oblique line on thyroid cartilage
Action: draws larynx downward
Innervated by anterior rami of C1-3 through ansa cervicalis
Thyrohyoid
Originates at oblique line on thyroid cartilage and inserts into greater horn and adjacent body of hyoid
Action: depresses the hyoid, can raise larynx when hyoid is fixed
Innervated by anterior rami of C1 but fibres run with CN XII
Branches of ECA
Superior thyroid artery
Ascending pharyngeal artery
Lingual artery
Facial artery
Occipital artery
Posterior auricular
Maxillary artery
Superficial temporal
Internal jugular vein
Exits skill via jugular foramen and enters carotid sheath
Drains these veins:
Inferior petrosal sinus
Pharyngeal
Occipital
Facial
Lingual
Superior thyroid
Middle thyroid
Then joins subclavian vein to come brachiocephalic vein
Thyroid gland supply and drainage
Arterial supply
- superior thyroid artery (branch of ECA)
- inferior thyroid artery (branch of thyrocervical trunk from subclavian)
Venous drainage
- superior thyroid vein (into IJV)
- middle thyroid vein (IJV)
- inferior thyroid vein (brachiocephalic)
Parathyroid gland supply and drainage
Arterial supply
- inferior thyroid arteries
Venous drainage
- superior thyroid vein
- middle thyroid vein
- inferior thyroid vein
Thyroid and parathyroid gland Innervation
Thyroid branches from the cervical (sympathetic) ganglia
Recurrent laryngeal nerve
Right artery loops around subclavian arteries and left loops around arch of aorta
Risk of iatrogenic damage during neck surgery
Posterior triangle boundaries
Anterior: posterior border of SCM
Posterior: anterior border of trapezius
Inferior: middle third of clavicle
Roof: deep investing fascia
Floor: prevertebral fascia
Trapezius
Originates at superior nuchal line, external occipital protuberance, ligamentum nuchae and spinous processes
Inserts at lateral third clavicle, acromion and spine of scapula
Action: assists is rotating scapula during abduction of humerus. Upper fibres elevate and middle abduct and lower depress scapula
Innervated by: spinal accessory nerve (CN XI)
Test by shrugging shoulders
Levator scapulae
Originates at C1-4 (transverse process)
Inserts at scapula (upper medial border)
Action: elevates scapula
Innervated by C3,4 and dorsal scapular nerve (C4,5)
Anterior and middle scalene
Anterior scalene
- originates at C3-6 (anterior tubercle of transverse processes)
- inserts at upper surface of rib 1 and scalene tubercle
Middle scalene
- originates at C4-7 (transverse processes)
- inserts into upper surface of rib 1
Action: elevate first rib
Innervated by anterior rami of C4-7 (both) and C3 (anterior)
Sternocleidomastoid
Origins
- sternal head: manubrium of sternum
- clavicular head: medial third clavicle
Inserts
- lateral surface of mastoid process of temporal bone and lateral half of superior nuchal line of occipital bone
Innervation
- accessory nerve
- branches of cervical plexus
Blood supply
- superior thyroid artery
Contents of posterior triangle
Spinal accessory nerve
Subclavian artery and vein
Brachial plexus trunks
Omohyoid muscle - inferior belly
Cervical plexus
Anterior rami of C1, C2-4
Has muscular branches and cutaneous branches
Muscular branches
- phrenic nerve (C3,4,5) - diaphragm
- ansa cervacilis (C1,2,3)
- branches to prevertebral and vertebral muscles
Cutaneous branches
- C2: lesser occipital nerves
- C2,3: greater auricular and transverse cervical nerves
- C3,4: supraclavicular nerves
External jugular vein
Origin: near the mandibular angle
Course: descends alongs neck and overlies the SCM then reaches clavicle
Tributaries: cervical, supra
scapular and anterior jugular veins
Drainage: drains into subclavian vein
Anterior jugular vein
Origin: near hyoid bone and arises from the joining of the superficial and submandibular veins
Course: goes down the neck and passes between midline of neck and anterior margin of SCM
Tributaries: laryngeal, small thyroid, inferior thyroid veins
Drains to external jugular vein
