1.3 Posterior triangle of the neck Flashcards
The posterior triangle of the neck lies behind the sternocleidomastoid (SCM):
• Muscles of the floor are covered by the prevertebral layer of the deep cervical fascia
What are the boundaries of the posterior triangle of neck?
- Floor: From top to bottom: splenius capitus, levator scapulae, scalenus posterior, scalenus medius, scalenus anterior, semispinalis capitis
Anterior (Posterior border of SCM), Posterior (anterior border of trapezius), Apex (superior nuchal line of occipital bone), base (middle third of clavicle), roof (skin, superficial fascia, platysma, investing layer of deep fascia), f
The inferior belly of omohyoid subdivides the posterior triangle into the upper large occipital triangle and the lower smaller supraclavicular triangle:
• Supraclavicular (subclavian) triangle contains the distal portion of the subclavian artery
What are the borders of the occipital and supraclavicular triangle?
Occipital (posterior border of SCM, trapezius, superior border of inferior belly of omohyoid)
Supraclavicular (posterior border of SCM, inferior border of inferior belly of omohyoid, middle third of clavicle)
what is in the posterior triangle?
- muscles
- nerves
- vessels
- muscles: Sternocleidomastoid (SCM), trapezius
- nerves: Cutaneous branches from cervical plexus, spinal accessory nerve (CN XI), phrenic nerve, roots and trunks of brachial plexus
- vessels: External jugular vein (EJV), subclavian vein, transverse cervical artery, suprascapular artery, third part of subclavian artery, occipital artery
what is the innervation of SCM and trapezius?
- Motor: spinal accessory nerve (CN XI)
- Sensory: C2 – C3 (pain and proprioception)
what are the functions of the SCM?
- Unilateral contraction: lateral flexion of neck + rotation of face in opposite direction
- Bilateral contraction: flexion of cervical vertebra (when supine)
what are the functions of the trapezius?
- Superior part: elevation of pectoral girdle, maintain shoulder levels
- Middle part: retraction of scapula
- Inferior part: depression of shoulders
The cervical plexus is an important group of nerves in the posterior triangle of the neck:
• Nerve loops of the cervical plexus arise from the _________________ (deep to the SCM)
• Divide as motor (deep branches → anteromedially) and cutaneous (superficial branches → posteriorly)
• Cutaneous nerves receive communicating branches from ________________
- C2 and C3: Emerge around the middle of the SCM → nerve point/Erb’s point of the neck (junction of the superior and middle thirds of SCM):
• Lesser occipital nerve (C2): supplies ________________ (communicates with great auricular nerve) → hooks around _______ and travels upwards
• Great auricular nerve (C2 – C3): supplies skin over parotids, posterior part of auricle, area between angle of mandible and mastoid process (winds around the __________; largest branch) → may be sacrificed during parotidectomies (causing numbness)
• Transverse cervical nerve (C2 – C3): supplies ________________
C3 and C4: Emerge behind the posterior border of the SCM (divides into 3):
• Supraclavicular nerves (C3 – C4): supplies __________________
anterior rami of C1 – C4 nerve roots;
superior cervical ganglion;
skin of neck and scalp postero-superior to the auricle ;
CN XI;
SCM;
skin over anterior neck;
skin over shoulder, supraclavicular fossa, upper thoracic region, sternoclavicular joint
The spinal accessory nerve (CN XI) passes deep to the SCM, and appears in the posterior triangle (runs across → highest nerve running in the posterior triangle) at the junction of the ______________________
• Lies deep to the investing layer of the deep cervical fascia, running on the levator scapulae muscle and disappears deep to the anterior border of the trapezius
• Innervation:___________________
superior and middle thirds of the SCM;
SCM and trapezius muscles (weakness if CN XI damaged)
The phrenic nerve (C3 – C5 roots) forms at level of the superior border of thyroid cartilage:
• Runs anterior to the ______________, deep to prevertebral layer of deep cervical fascia
• Left side: crosses anterior to the ____________; right side: crosses anterior to the s__________________
• Motor innervation: diaphragm; sensory innervation: mediastinal pleura, thoracic pericardium, central part of diaphragm
scalenus anterior muscle;
first part of the subclavian artery;
econd part of the subclavian artery
The brachial plexus is formed by the union of the C5 – T1 nerve roots (between the scalenus anterior and medius muscles):
• Roots and trunks are in the posterior triangle of the neck, along with several branches (________________ supplying rotator cuff and ___________ supplying serratus anterior)
• Innervates the upper limbs and scapular region
suprascapular nerve ;
long thoracic nerve
The external jugular vein (EJV) is formed by the union of the _______________________:
• Lies deep to the platysma and anterior to the SCM and terminates in the subclavian vein (drains into the brachiocephalic vein then SVC) behind the clavicle
• Drains the scalp and face
• Tributaries: __________________
Distended EJV: occurs due to elevated central venous pressure (which may be due to impaired filling of RA, stenosis of SVC, constrictive pericarditis, cardiac tampo nade, right heart failure)
- Important diagnostic sign for several conditions (elevated
posterior division of the retromandibular vein and posterior auricular vein (lies in front of SCM);
posterior external jugular vein, transverse cervical vein, suprascapular vein, anterior jugular vein
The subclavian veins are continuations of the axillary veins and joins with the IJV to form the brachiocephalic veins (drain into SVC):
• Extends from the outer border of 1st rib to the medial border of scalenus anterior
What are the tributaries of the subclavian vein?
external jugular vein (EJV), dorsal scapular vein, anterior jugular vein, thoracic duct (on left side), right lymphatic duct
The most accessible segment of the subclavian artery lies in the supraclavicular triangle:
• Extends from the lateral margin of the ___________ to the outer border of the ____________, and continues as the axillary artery
• Originates from the brachiocephalic trunk (right side) and the aortic arch (left side)
• Pulsations can be felt at the antero-inferior angle of the posterior triangle
• May be compressed against the 1st rib (with the shoulder depressed)
What are the tributaries of the subclavian artery?
scalenus anterior;
1st rib;
First part (medial to scalenous anterior)
- Vertebral artery
- internal thoracic artery
- thyrocervical trunk
- costocervical trunk (left side)
2nd part
- costocervical trunk (right side)
3rd part
- dorsal scapular artery (supplies rhomboids)
what are branches of the thyrocervical trunk
- transverse cervical artery (anterior to phrenic nerve and scalenous anterior muscle)
- suprascapular artery (crosses the scalenous anterior muscle)
The supraclavicular nodes lie along the ____________, draining the lymph from the back of scalp and posterior neck:
• Communicates with the __________________ and finally drains into the lymphatic duct and thoracic duct
• May be involved in breast cancer, advanced tumours of the lungs, alimentary tract (especially Virchow’s node) and the gonads
inferior belly of omohyoid;
axillary group of lymph nodes, jugulo-omohyoid group,
