Lecture 5 - Anterior triangle of neck Flashcards
Anterior triangle - why is it important
- goitre (thyroid enlarged)
- Central vien catherterisation - can put through 2 heads of sternocleidomastoid
- Penetrating trauma
- cricothyroidotomy
Muscles in anterior triangle
Infrahyoid (strap muscles) - Sternohyoid, omohyoid, thyrohyoid, sternothyroid
Suprahyoid - stylohyoid, digastric, mylohyoid, geniohyoid
Cervical plexus
Ansa cervicalis
C1-C4
Ansa cervicalis - loop fomred by C1- C3
Superior root - (C1) - innovates one muslce (infrahyoid - shorter)
Inferior root (c2-c3) - longer muscles of the neck - omohyoid, sternohyoid, sternothyroid
-rest of cervical plexus - sensory component of neck
Phrenic nerve - some contribution from this plexus
Where does the thyroid sit?
isthmus sits at 2-3 tracheal cartilage
thyroid cartilage is above this
-if cut the thyroid need to know that cartilage is below
Blood supply to thyroid
why important?
- Superior and inferior thyroid artery
- superior is the first branch off the external carotid
- Inferior thyroid - comes off from thyrocervical branch, a branch of subclavian artery
Ima artery - to isthmus - comes from subclavian - need to make sure this artery is not here
When do a thyroidectomy, need to ligate these arteries
Venous arteries - usually after operation the bleeding is coming from these arteries
Venous drainage - superior and middle- drains to IVC, and inferior drains to left brachiocephalic vien
**
Subclavian artery branches (exam Q)
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**
Lymphatic drainage of thyroid
paratracehal and deep cervical lymph nodes
Innervation of thyroid
sympathetic - middle cervical ganglion (runs with arteries)
parasympathetic - vagus (recurrent laryngeal nerve - runs in a groove between oesophagus and the trachea)
Embryology of thyroid
starts as foreamen caecu at base of tongue as the thyroglossal duct, then it travels down past hyoid bone
- then reaches final destination which is anterior to trachea of neck
- tyroglossal duct usually disappears but if it doesn’t can get food here
Suprahyoid muscles
Important - because they form the floor of the mouth
between hyoid bone and mandible
Superficial - anterior belly of digastric
myohyoid muscle
genohyoid (deepest)
Posterior belly of digastric and stylohyoid
Styloid process - what attaches
stylohyoid attaches here
-innovated by facial nerve
Mylohyoid and anterior belly of digastric - nerve supply
V3
Geniohyoid muscle - nerve supply and what other muscle is stimulated by this?
C1, thyrohyoid
** What forms the external jugular vien? (need to know for exam)
posterior auricular and retromandibular
Pathways for different cranial nerves
MUST MEMORISE THESE!!!
Path of glossopharyngeal nerve
Jugular foreamen deep to styloid process internal and external carotid arteries curves around lateral border of stylopharyngeus goes to base of tonuge
Path of vagus nerve
jugular foreamen
between 9,11
runs in carotid sheath betewen internal carodi arter and internal jugular vien
root of neck - passes in front of subclavian artery and behind subclaian vien to enter the mediastinum
**Path of accessory nerve
jugular foreamen posteiror to 9
runs poserolaterally either medial or lateral to inernal jugular vien in cartodi sheath
-crosses transverse prceoss of atlas and passes medial to styloid process and postteiror belly of digastric to perforate the sternocleidomastoid muscle and reach the posterior triangle of the neck
Path of hypoglossal nerve
hypoglossal foreamen
between inernal cartoid artery and internal jugular vien and crosses 3 artiers (cocipital, external carotid and lingual arteries)
-deep to posteiror belly of digastric to reach the tongue
-branch from anterior rami of C1 hitchhikes with it
-this branch innervates some of the suprahyoid muscules thyrohyodi and genio hyoid
** Surface anatomy of thyroid
The thyroid cartilage is found between vertebral levels C3-C4, the lower edge of this (C4) is also where the carotid bifurcation is found. The hyoid bone is found at level C3.
The internal jugular can be distinguished from the carotid on ultrasound by using the valsalva manoeuvre in which the patient is asked to blow on their thumb. The diameter of the carotid artery should remain the same, but the internal jugular will inflate.
The thyroid gland is found at vertebral levels C5-T1
