2. Posterior and anterior triangles of the neck, thyroid, parathyroid Flashcards by Alix Wrighton

Boundaries of the anterior triangle of the neck?

Bounded by inferior border of mandible, anterior border of SCM & midline of neck

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What fascia forms the roof and floor of the anterior triangle?

Roof= Deep investing fascia around muscles
Floor= Pretracheal fascia and carotid sheath

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What are the 4 subdivisions of the anterior triangle?

Submandibular, submental, carotid & muscular triangles

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What are the contents of the submandibular subdivision of the anterior triangle?

Contains submandibular gland, lymph nodes, (parts of) CN XII, mylohyoid nerve & parts of the facial artery & vein

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What are the contents of the submental subdivision of the anterior triangle?

Submental lymph nodes

Small veins

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What are the contents of the carotid subdivision of the anterior triangle?

Contains thyroid gland, larynx, pharynx, carotid sheath (& its contents), branches of cervical plexus, superior root of the ansa cervicalis, deep cervical lymph nodes & (parts of) CN XI & XII

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What are the contents of the muscular subdivision of the anterior triangle?

Muscles: Sternothyroid and Sternohyoid
Glands: Thyroid and parathyroid

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Which bone divides the muscles of the anterior compartment?

The hyoid bone, all are either:

above and connect to skull or mandible
Below and connect to inferior structure (e.g. sternum, scapula, thyroid, cartilage)

Except: Sternothyroid

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Name the 8 muscles above and below the hyoid bone in the anterior compartment of the neck?

Suprahyoid muscles

Mylohyoid
Digastric
Stylohyoid
Geniohyoid

Infrahyoid muscles

Sternohyoid
Omohyoid
Thyrohyoid
Sternothyroid*

*Sternohyoid doesn’t attach to the hyoid bone. Attaches from sternal notch to the thyroid cartilage

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Action of suprahyoid muscles

Raise the hyoid bone as required during swallowing

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Attachment and action of the mylohyoid bone?

Mylohyoid originates at mylohyoid line on mandible; inserts into body of hyoid & fibres of opposite mylohyoid

Actions:
Elevates the hyoid & the floor of the mouth
Supports floor of mouth

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Digastric:
Bellies?
Attachments?
Actions?

Bellies: Anterior and posterior

ANTERIOR BELLY
Attachment: From digastric fossa on lower meal aspect of mandible to intermediate tendon at hyoid
Action: Raises hyoid and opens mouth by lowering mandible

POSTIOR BELLY
Attachment: Mastoid notch on medial side of mastoid process to the intermediate tendon at the hyoid bone
Action: Elevates and retracts hyoid bone

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Innervation of mylohyoid?

Nerve to mylohyoid i.e. inferior alveolar branch of CN V3

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Innervation of anterior belly of digastric?

Nerve to mylohyoid i.e. inferior alveolar branch of CN V3

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innervation of posterior belly of digastric?

Digastric branch of CN VII

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Stylohyoid:
Attachment?
Action?
Innervation?

Stylohyoid originates at the styloid process & inserts into body of hyoid (laterally)
Action: Pulls hyoid bone upward (posterosuperior direction)
Innervation via CN VII

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Innervation of surpahyoid muscles?

Suprahyoid muscles

Mylohyoid: inferior alveolar branch of CN V3
Digastric: Ant belly (inferior alveolar branch of CN V3), Post belly (Digastric branch of CN VII)
Stylohyoid: CN VII
Geniohyoid: Anterior ramus of C1 (travels via CN XII)

Geniohyoid muscle:
Attachment?
Action?
Innervation?

Geniohyoid originates from the mandible (mental spine) & inserts at body of hyoid (located superior to mylohyoid)

Actions:
Fixed mandible – elevates & pulls hyoid forward
Fixed hyoid – pulls mandible downward & inward

Innervation:
Anterior ramus of C1 (travels via CN XII)

Role of infrahyoid muscles?

Depress or fix hyoid bone
+
Provide attachment for suprahyoid muscles

Attachment of sternohyoid?

Action?

Sternohyoid originates at posterior surface of sternoclavicular joint & manubrium; inserts into body of hyoid medially
Action: Depresses hyoid after elevation during swallowing

Omohyoid:
Bellies?
Attachment?
Action?

Bellies: Inferior and superior

SUPERIOR BELLY: Attaches from intermediate tendon and inserts as body of hyoid laterally.

INFERIOR BELLY:
originates at superior border of scapula & inserts/ends at its intermediate tendon in posterior triangle)

Note: intemediate tendon attaches to the clavicle with a fascial sling

Actions: Depresses and fixes the hyoid

Thyrohyoid:
Attachment?
Actions?

Thyrohyoid originates at oblique line on thyroid cartilage; inserts into greater horn & adjacent body of hyoid

Actions:
Depresses the hyoid
Raises larynx when hyoid is fixed

Sternpthyroid:
Attachment?
Action?

Sternothyroid originates at posterior surface of manubrium; inserts into oblique line on thyroid cartilage
Action: Draws the larynx downward

Innervation of the infrahyoid muscles in the anterior triangle?

Sternohyoid, omohyoid & sternothyroid are innervated by anterior rami of C1 to C3 (through the ansa cervicalis )

Thyrohyoid: From anterior rami of C1 but fibres run with CN XII

What structures make up the thyroid gland?

• 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 compartment is the thyroid gland within?

within the visceral compartment surrounded by pretracheal fascia

Arterial supply to thyroid artery?

Arterial supply: • Superior thyroid artery (1st branch of external CA) • Inferior thyroid artery (branch of thyrocervical trunk from subclavian)

Venous drainage of the thyroid artery?

``` Venous drainage (thyroid venous plexus): • Superior thyroid vein (into IJV) • Middle thyroid vein (into IJV) • Inferior thyroid vein (into brachiocephalic) ```

Position of the parathyroid gland?

Two pairs (superior & inferior) of small glands usually on posterior surface of thyroid, but exact position varies 4 in total/

Arterial supply and venous drainage of parathyroid artery?

Arterial supply: Inferior thyroid arteries (branch of thyrocervical trunk from subclavian) ``` Venous drainage (same as thyroid gland): • Superior thyroid vein (into IJV) • Middle thyroid vein (into IJV) • Inferior thyroid vein (into brachiocephalic) ```

Innervation of the parathyroid and thyroid gland?

From the thyroid branches of the cervical (symp) glanglia

Border of the posterior triangle?

Anterior: Post border of SCM Posterior: Ant borfer of trapezius Inferior: Middle 1/3 of clavicle Superior: occipital bone Is in direct continuity with upper limbs

Which fascia for the roof and floor of the posterior triangle of the neck?

Roof: deep investing fascia around muscles (SCM & trapezius) Floor: (muscular) prevertebral fascia surrounding splenius capitus, levator scapulae, scalenes

Innervation of roof and floor muscles of the posterior triangle of the neck?

Roof: SCM & trapezius from CN XI Floor: Splenius capitus, levator scapulae, scalenes from cervical nerves

Sternocleidomastoid: Attachment? Action? Innervation?

• Sternal head originates at manubrium of sternum & inserts lateral half of the superior nuchal line • Clavicular head originates at medial 3rd of clavicle & inserts into lateral surface of mastoid process Actions: Draws the head forward (both SCMs); or tilts head toward ipsilateral shoulder while turning face contralaterally (one SCM) Innervated by spinal accessory nerve (CN XI)

Trapezius: Attachment? Action? Innervation?

rapezius originates at superior nuchal line, external occipital protuberance, ligamentum nuchae & spinous processes (C7-T12); inserts into lateral 3rd of clavicle, acromion & spine of scapula Actions: Assists in rotating scapula during abduction of humerus; upper fibres elevate, middle adduct & lower depress scapula Innervated by spinal accessory nerve (CN XI)

Levator scapulae: Attachment? Action? innervation?

Levator scapulae originates at C1-C4 (transverse processes); inserts into scapula (upper medial border) Action: Elevates scapula Innervated by C3, C4, & dorsal scapular nerve (C4, C5)

Anterior scalene: Attachment? Action? Innervation?

Anterior scalene originates at C3-C6 (anterior tubercle of transverse processes); inserts into upper surface of rib 1 & scalene tubercle Action: Elevates 1st rib Innervation: Anterior rami of C3-C7

Middle scalene: Attachment? Action? Innervation?

Middle scalene originates at C4-C7 (transverse processes); inserts into upper surface of rib 1, posterior to groove for SCA Action: Elevates 1st rib Innervation: Anterior rami of C4-C7

What are the cutaneious and muscular branches of the anterior rami of C1-C4 of the cervical plexus?

``` Muscular branches: Phrenic nerve (C3, C4, C5) Ansa cervicalis (C1, C2, C3) branches to prevertebral & vertebral muscles ``` Cutaneous branches: C2 – lesser occipital nerves C2, C3 – great auricular & transverse cervical nerves C3, C4 – supraclavicular nerves **great auricular supplies the angle of the mandible*

``` Ansa Cervicalis (anterior rami of C1-C3) Superior & inferior roots Innervates which muscle of the anterior triangle? ```

Infrahyoid muscles

Difference in drainage of anterior and external jugular vein?

Anterior jugular vein drains into the external jugular vein External jugular vein drains into the subclavian vein