Neck Triangles

Question 1

Hyoid bone

Answer 1

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

Question 2

Anterior triangle boundaries

Answer 2

Superiorly: inferior border of mandible

Laterally: anterior border of SCM

Medially: sagittal line down midline of neck

Roof: deep investing fascia

Floor: pretracheal fascia

Question 3

Anterior triangle subdivision

Answer 3

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

Question 4

Suprahyoid muscles

Answer 4

Raise the hyoid bone as required during swallowing

Mylohyoid
Digastric
Geniohyoid
Stylohyoid

Question 5

Mylohyoid

Answer 5

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

Question 6

Digastric

Answer 6

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

Question 7

Stylohyoid

Answer 7

Originates at the styloid process

Inserts into body of hyoid (laterally)

Action: pulls hyoid bone upwards posterosuperiorly

Innervation: CN VII

Question 8

Geniohyoid

Answer 8

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)

Question 9

Infrahyoid (strap) muscles

Answer 9

Depress or fix hyoid bone and provide attachment for suprahyoid muscles

Sternohyoid
Sternothyroid
Thyrohyoid
Omohyoid

Question 10

Sternohyoid

Answer 10

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

Question 11

Omohyoid

Answer 11

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

Question 12

Sternothyroid

Answer 12

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

Question 13

Thyrohyoid

Answer 13

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

Question 14

Branches of ECA

Answer 14

Superior thyroid artery
Ascending pharyngeal artery
Lingual artery
Facial artery
Occipital artery
Posterior auricular
Maxillary artery
Superficial temporal

Question 15

Internal jugular vein

Answer 15

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

Question 16

Thyroid gland supply and drainage

Answer 16

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)

Question 17

Parathyroid gland supply and drainage

Answer 17

Arterial supply
- inferior thyroid arteries

Venous drainage
- superior thyroid vein
- middle thyroid vein
- inferior thyroid vein

Question 18

Thyroid and parathyroid gland Innervation

Answer 18

Thyroid branches from the cervical (sympathetic) ganglia

Question 19

Recurrent laryngeal nerve

Answer 19

Right artery loops around subclavian arteries and left loops around arch of aorta

Risk of iatrogenic damage during neck surgery

Question 20

Posterior triangle boundaries

Answer 20

Anterior: posterior border of SCM
Posterior: anterior border of trapezius
Inferior: middle third of clavicle
Roof: deep investing fascia
Floor: prevertebral fascia

Question 21

Trapezius

Answer 21

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

Question 22

Levator scapulae

Answer 22

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)

Question 23

Anterior and middle scalene

Answer 23

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)

Question 24

Sternocleidomastoid

Answer 24

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

Question 25

Contents of posterior triangle

Answer 25

Spinal accessory nerve
Subclavian artery and vein
Brachial plexus trunks
Omohyoid muscle - inferior belly

Question 26

Cervical plexus

Answer 26

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

Question 27

External jugular vein

Answer 27

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

Question 28

Anterior jugular vein

Answer 28

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