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Triangles of the Neck Week 10 dissection

Terms in this set (33)

Platysma
-belongs to muscles of facial expression
-depresses mandible (corners of the mouth)
-tightens skin of neck
-innervated by cervical branches of the facial nerve
Trapezius
-Elevates, depresses, retracts, and rotates the scapula
-Works with other thoracic and upper limb muscles
-innervated by CN XI
Sternocleidomastoid
-unilateral contraction causes face to turn to contralateral side, head tilts to ipsilateral side. Bilateral contraction causes flexion of the head.
-innervated by CN XI (accessory nerve)
infrahyoid muscles
sternohyoid, omohyoid, sternothyroid, thyrohyoid
function of infrahyoid muscles
-depress hyoid bone & elevates & depresses larynx, thus helping you swallow
suprahyoid muscles
digastric, stylohyoid, mylohyoid, geniohyoid
function of suprahyoid muscles
elevate hyoid
Mylohyoid
-elevate the hyoid bone, elevate the oral cavity, and depress the mandible
-innervated by the inferior alveolar nerve
Geniohyoid
-elevates hyoid bone and larynx with it.
-innervated by a branch of the ventral ramus of C1 from the cervical plexus
Stylohyoid
-elevates and retracts hyoid bone
-innervated by stylohyoid branch of facial nerve
Digastric
-elevates hyoid and depresses mandible
-anterior belly innervated by inferior alveolar nerve
posterior belly
-innervated by the digastric branch of facial nerve
Sternohyoid
-depresses hyoid bone and laryngeal skeleton, fixes hyoid so the suprahyoid muscles can act on the mandible using the hyoid as a fixed attachment
-innervated by C1-C3 branch of ansa cervicalis
Sternothyroid
-depresses hyoid bone and laryngeal skeleton, fixes hyoid so the suprahyoid muscles can act on the mandible using the hyoid as a fixed attachment
-innervated by ventral rami of C1-C3 branch of ansa cervicalis
Omohyoid
-depresses hyoid bone and laryngeal skeleton, fixes hyoid so the suprahyoid muscles can act on the mandible using the hyoid as a fixed attachment
-superior belly innervated by C1 of ansa cervicalis, inferior belly innervated by C1, C2 and C3 of ansa cervicalis
Thyrohyoid
-depresses hyoid bone and laryngeal skeleton, fixes hyoid so the suprahyoid muscles can act on the mandible using the hyoid as a fixed attachment
-innervated by C1 fibres of ansa cervicalis, via the hypoglossal nerve
What does the external jugular vein drain and where does it drain to?
Drains blood from the face and scalp into the subclavian vein.
Why does a Valsalva's manoeuvre make the external jugular vein stand out?
Increased thoracic pressure/increased pressure in veins of thorax, so venous return to the heart is decreased.
If you could see the external jugular vein on a patient while they were sitting in your dental chair what might you suspect about their medical history?
Congestive heart failure
What would happen to the external jugular vein on such a patient if you put them into a reclined position?
Becomes more visible due to reduced venous return
Why is the blood supply to the thyroid gland so rich?
It is an endocrine gland - it secretes substances directly into the blood
Which aspect of the gland do its arteries enter?
Superior - at the pole of each lobe
Inferior - at their posterior borders
Where do the thyroid arteries arise from?
Superior - external carotid artery
Inferior - subclavian artery
Do the thyroid arteries supply anything other than the thyroid?
Superior thyroid artery branches to form the hyoid artery, sternocleidomastoid artery and superior laryngeal artery
Why is only part of the thyroid removed for benign lesions affecting the gland? Which part is left? Why?
Leave posterior region so that blood vessels still enter, contains parathyroids that are involved in calcium homeostasis
What type of nerve is the accessory nerve? Where does it come from? What does it supply?
-cranial nerve XI.
-arises at C1-C5/C6
-enters the cranium through foramen magnum before existing through the jugular foramen.
-It supplies motor innervation to sternocleidomastoid and trapezius.
Which spinal nerves contribute to the cervical plexus?
C1-C4
What do the other cervical spinal nerves (other than C1-C4) contribute to?
C5-C8 + T1 form the brachial plexus
Clinical question:
While you are carrying out routine treatment of a patient, the patient "collapses" in the chair and starts fighting for breath. Remembering the A B C of first aid, you check their airway and there is no obvious obstruction in the mouth. They are trying to breath but no air seems to be entering or leaving the lungs. You check their circulations by taking their pulse. Where would you take their pulse in such a situation?
Carotid pulse
Clinical question:
You decide that the patient has gone into laryngeal spasm and that you are going to cut into the respiratory tract because the larynx is blocked and the patient is asphyxiating.
Where would you make the incision?
Where would you NOT make an incision?
Cricothyroid membrane. Do not make the incision laterally or inferiorly as you may damage the thyroid gland
An 18 year old male is admitted to the maxillofacial unit you are working in following an RTA. He has extensive facial damage and deep lacerations in his neck over the posterior triangle. What nerves may have been damaged by the lacerations?
Branches of the facial, trigeminal and accessory nerves.
How would you test the facial, accessory and trigeminal nerves for damage?
Facial - exaggerated facial expressions
Trigeminal - sharp/blunt test over face and ask patient to protrude jaw V3 supplies muscles of mastication!)
Accessory - shrug shoulders/turn head against resistance
When you are taking the medical history of a 45 year old female patient, she reports that she had a partial thyroidectomy two months ago for an underactive thyroid. You notice that her voice lacks power and is croaky - rather like a creaky whisper. She says that it came on after her operation and that the ENT consultant has referred her to a speech therapist in a few weeks time.
What structures may have been damaged during the operation? Give reasons.
Recurrent laryngeal nerve - it returns to larynx in the groove between the trachea and esophagus
Why will her voice be "croaky"?
The recurrent laryngeal nerves innervate muscles of larynx except for cricothyoid. Interarytenoids receive bilateral innervation and so vocal folds will be partially adducted and tensed.
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