Station 4 Flashcards
What are the boundaries of the posterior triangle?
Anterior: posterior border of SCM
Posterior: anterior border of trapezius muscle
Inferior: middle 1/3 of clavicle
What two subdivisions/triangles does the posterior triangle split into? What divides these two triangles?
Occipital triangle and subclavian triangle - split by the inferior belly of the omohyoid muscle
Which main vein sits in the posterior triangle?
External jugular vein
Which cranial nerve traverses the posterior (occipital) triangle?
Accessory nerve (CNXI)
Which muscles do the accessory nerve (CNXI) innervate?
SCM and trapezius
Which two plexuses form the floor of the posterior triangle?
Cervical plexus (incl phrenic nerve therefore must be v careful when doing cervical plexus nerve block) Brachial plexus
Which vein does the external jugular vein drain into?
Subclavian vein
Where does the scalenus anterior muscle attach inferiorly?
1st rib
What are the four divisions/triangles of the anterior triangle?
- Carotid triangle
- Submental triangle
- Submandibular triangle
- Muscular triangle
What are the boundaries of the anterior triangle?
Superiorly: inferior border of the mandible
Laterally: medial border of sternocleidomastoid
Medially: sagittal line down midline of body
What are the boundaries of the carotid triangle?
Superior: posterior belly of digastric muscle
Lateral: medial border of SCM\
Inferior: superior belly of omohyoid muscle
What are the contents of the carotid triangle?
Carotid sheath:
Common carotid artery
Internal jugular vein
Vagus (CNX) nerve
Hypoglossal (CNXII) nerve
Carotid sinus (IX) baroreceptors
What is the carotid sinus?
A dilated portion of the common carotid and internal carotid arteries. It contains baroreceptors that detect stretch as a measure of BP. CNIX (glossopharyngeal) feeds this info to the brain and uses it to regulate BP.
Some people have hypersensitive baroreceptors - external pressure on the carotid sinus can cause bradycardia and hypotension. Therefore checking the pulse at the carotid triangle is not advised.
What structures does the carotid sheath contain?
Common carotid artery (bifurcates within the sheath into ext/int CA)
Internal jugular vein
Vagus nerve (CNX)
Cervical lymph nods
At what level does the common carotid artery bifurcate?
Superior margin of the thyroid cartilage (C4)