AH&N- The Triangles Of The Neck Flashcards
What are the muscles in the posterior triangle?
Omohyoid: split into 2 bellies by a tendon, the inferior belly crosses posterior triangle travelling superomedial direction & split triangle in 2. Crosses under the SCM & enters anterior triangle.
Floor of triangle: splenius captitis, levator scapulae, anterior, middle and posterior scalene.
What vasculature is present within the posterior triangle?
External jugular vein: formed by retromandibular and posterior auricular veins, lies superficially after crossing the SCM, it pierces the investing layer of fascia and empties into the subclavian vein.
Subclavian, transverse cervical & suprascapular veins.
Subclavian- point of access via a central catheter
Distal part of subclavian artery- emerges between anterior & middle scalene muscles- crosses 1st rib: axillary artery
Suprascapular & transverse cervical arteries: base of posterior triangle.
What happens when the external jugular vein is severed?
It’s lumen is maintained by the thickened tough layer of investing fascia.
Air will be drawn into the vein, filling the RA & ventricle with froth inducing central cyanosis
To prevent worsening & death, firm pressure must be applied to the vessel to stop the bleeding and entry of air.
What nerves are present in the posterior triangle?
Accessory nerve: exits cranial artery and descends down neck, innervates SCM, enters posterior triangle & crosses inferoposterior direction within the investing fascia, lies superficially, danger of injury.
Cervical plexus: within muscles of the floor, major branch is the phrenic nerve, descend down neck within paraverteral fascia
What is cervical plexus block?
For anaesthesia of the neck area a cervical plexus block is used.
An anesthetic is injected along the posterior border of the SCM particularly at the junction of its superior and middle thirds.
This junction is where the cutaneous branches of the cervical plexus emerge & is known as the nerve point of the neck.
Not usually carried out on patients with pulmonary or cardiac problems as it damages the phrenic nerve.
What are the borders of the posterior triangle?
Anterior: posterior border of the SCM
Posterior: anterior border of the trapezius muscle
Inferior: middle 1/3 of the clavicle
Covered by the investing fascia and the floor is formed by prevertebral fascia
What are the two subdivisions of the posterior triangle?
Omohyoid muscle splits the posterior triangle into 2: a superior & inferior part. Superior part (occipital triangle): larger Inferior triangle (subclavian triangle): contains distal part of subclavian artery
What are the borders of the anterior triangle?
Superior: inferior border of the mandible
Lateral: medial border of the SCM
Medial: imaginary sagittal line down midline of body
Which suprahyoid muscles are in the anterior triangle?
Stylohyoid, digastric, mylohyoid, geniohyoid
Which infrahyoid muscles are in the anterior triangle?
Omohyoid, sternohyoid, thyrohyoid, sternothyroid
What vasculature is present in the anterior triangle?
Common carotid artery, bifurcates in triangle, external & internal carotid arteries.
Internal jugular vein.
What nerves are present in the anterior triangle?
Facial nerve Glossopharyngeal nerve Vagus nerve Accessory nerve Hypoglossal nerve
What are the subdivisions of the anterior triangle?
Carotid
Submental
Submandible
Muscular
What are the borders of the carotid subdivision of the anterior triangle?
Superior: posterior belly of the digastric muscle
Lateral: medial border of the SCM
Inferior: superior belly of the omohyoid muscle
What is the clinical relevance of the carotid subdivision?
Vessels and nerves are relatively superficial & can be accessed by surgery.
Also contains the carotid sinus, dilated portion of the common and internal carotid arteries, contains baroreceptors that detect stretch as a measure of bp, glossopharyngeal nerve feed info to brain & regulates bp
In some baroreceptors are hypersensitive to stretch & external pressure on carotid sinus, can cause slowing of heart rate & decrease in bp, brain becomes underperfused & syncope results. In such patients checking the pulse at the carotid triangle is not advised.
