Triangles of Neck: Learning Objectives Flashcards
What are the boundaries of the anterior/posterior triangle of the neck? What muscle separates the
anterior from the posterior triangle?
Boundaries of Anterior Triangle:
Superior - inferior margin of mandible
Inferior- Jugular Notch
Medial- anteriomedian line of the neck
Lateral- anterior margin of sternocleidomastoid
Anterior- platysma m. and investing layer of fascia
Boundaries of Posterior Triangle:
Anterior- posterior margin of sternocleidomastoid m.
Posterior- anterior margin of trapezius
Inferior- middle 1/3 of clavicle
Roof- platysma m. and deep investing cervical fascia
Floor- splenius capitus m., levator scapulae m., scalenuis m.
The muscles that separates the two triangles is the sternocleidomastoid m.
What muscles form the floor of the posterior triangle?
The splenius capitus m.,levator scapulae m., and scalenuis m.
List the suprahyoid/infrahyoid muscles and their innervation.
Suprahyoid Muscles:
Digastric m.
-Ant. belly -n. to mylohyoid from trigeminal (CN V)
-Post. belly -facial nerve (CN VII)
Mylohyoid m.
-n. to mylohyoid from trigeminal (CN V)
Stylohyoid m.
-facial n. (CN VII)
Geniohyoid m.
-C1 via Hypoglossal n. (CN XII)
Infrahyoid Muscles:
Sternohyoid m.
-ansa cervicalis
Sternothyroid
-ansa cervicalis
Thryohyoid
-C1 via hypoglossal n. (CN XII)
Omohyoid
-ansa cervicalis
What are the functions/actions of the suprahyoid and infrahyoid mm.?
The suprahyoid mm. stabalize the hyoid bone and elevate it. They also depress the mandible.
The infrahyoid mm. stabalize the hyoid bone and larynx and thyroid and depress all three.
Which spinal cord levels are involved in the cervical plexus?
Ventral primary rami of C1-C4.
Where is a cervical block administered? Why?
The cervical nerve block is administered at the nerve point of the neck, which is along the posterior margin of the sternocleidomastoid m. at the superior and middle 1/3 of the muscle.
What forms the superior and inferior roots of ansa cervicalis?
The superior root is formed by C1 and/or C2. Inferior root is C2 and C3.
What vessel is often the point of entry to the venous system for central line placement?
Internal jugular vein
What are the branches of the external carotid artery in the neck? What does each supply?
Superior Thyroid a. - thyroid
Lingual a. - tongue and mouth
Facial a. - supplies superficial muscles of facial expression
below the nose.
Ascending pharyngeal a. - pharynx
Occipital a.- back of scalp and sternomastoid mm.
Posterior auricular a.- scalp post. to auricle and auricle itself
Maxillary a.- deep structures of the face (maxillary teeth,
gums, and palate)
Superficial temporal a. -temple, scalp
Where is the carotid pulse taken?
Carotid Triangle (a subdivision of the anterior cervical triangle)
List the 10 mm of the Anterior Triangle
- (2) Cerivcal mm = Platysma and SCM
- (4) Suprahyoid mm = Diagastric (Ant and Post bellies), Mylohyoid, Stylohyoid, and Geniohyoid
- (4)Infrahyoid mm = Thyrohyoid, Omohyoid (Superior belly only!), Sternohyoid, and Sternothyroid
List the 6 mm of the Posterior Triangle
- Splenius capitus
- Levator scapulae
- Anterior, Middle, and Posterior Scalenes
- Inferior belly of Omohyoid
Be able to label a diagram indicating the various subdivisions of the anterior triangle. What are the boundaries of each triangle?
(4) subtriangle pairs of Anterior cervical triangle (see ppt slide 5):
- Muscular Triangles–superior belly of omohyoid (lateral); inframedial edge of SCM (inferiolateral), anterior median line of neck (medial) and hyoid bone (superior)
- Carotid Triangles–posterior belly of Diagastric (superior); superior belly of omohyoid (medial); and medial border of SCM (lateral)
- Submandibular (Digastric!) Triangles–bounded by both bellies of Digastric m and by mandible (superior)
- Submental (suprahyoid) Triangles–anterior median line of neck (medial); anterior belly of Digastric (lateral); and hyoid bone (inferior)
List the contents of the Muscular subtriangle
All 4 infrahyoid strap mm (sternohyoid, sternothyroid, thryohyoid, and superior belly of omohyoid) and the Thyroid gland. Contains NO vessels!
List the contents of the Carotid subtriangle
Common Carotid A
Carotid Sinus
Internal Jugular Vein
CN X and CN XII
List the contents of the Submandibular (digastric) subtriangle
Submandibular gland
Facial artery and Facial vein
List the contents of the Submental subtriangle
Only lymph nodes
Identify the superficial and deep groups of the infrahyoid mm
- the 2 most superficial mm are the Sternohyoid and Omohyoid (Superior belly)
- the Thyrohyoid originates deep to the Sternohyoid and Omohyoid, but arises lateral to Omohyoid’s superior belly to insert on the hyoid bone
- the Sternothyroid is deep to the Sternohyoid
The carotid triangle provides surgical access to what anatomical structure
- the Carotid system of arteries
- IVJ
- Vagus and hypoglossal nn
- and the cervical sympathetic trunk
What are the (4) sensory branches of the cervical plexus? Be able to identify the regions on the neck they would innervate on a diagram.
- Great Auricular n (C2-C3): around inferior aspect of ear; parotid sheath
- Transverse cervical n (C2-C3): anterior skin of neck
- Supraclavicular n (C3-C4): skin over clavicle and shoulder
- Lesser occipital n (C2): scalp behind ear
How is the ansa cervicalis formed? Over what structure is the ansa formed? What does the ansa do?
[Remember: Cervical Plexus is formed by the ventral primary rami of C1-C4.} It’s motor branches come together anteriorly to form Ansa cervicalis– loop of superior root (C1 and/or C2) + inferior root (C2 and C3). Formed on top of IJV. It gives off 4 branches of motor inn to sternothyroid, sternohyoid, and omohyoid (BOTH sup and inf bellies)
What is congenital torticollis?
Congenital torticollis refers to SCM fibrosis (a fibrous tissue tumor) resulting in no lengthening of the SCM during embryological development. It presents like a normal unilateral SCM contraction with head tilted towards and face turned away from the affected side.
Where can the spinal accessory nerve be damaged? How does this present clinically?
CN XI is the most common iatrogenic (caused by physician) nerve injury. Can be damaged during extensive cervical dissections in posterior cervical triangle. For ex, during removal of cancerous lymph nodes.
Presentation: Shouler droop is most obvious sign of CN XI injury. Also, weakness in turning head to opposite side against resistance.
Does the internal carotid artery have any branches in the neck? How does the internal carotid artery enter the base of the skull–through what opening?
The internal carotid artery sends NO branches into the neck. It supplies the brain (along w/ vertebral aa). It enters the cranial cavity through the carotid canal in the petrous part of the temporal bone.
