Posterior Triangle of the Neck and Fascial Layers Flashcards
Superficial Fascia of the Neck
Immediately deep to skin (subcutaneous tissue)
- Comprised of loose connective tissue & fat
- Thinner than other areas of the body
Platysma m.
Platysma m. in the subcutaneous tissue
- Similar to scalp and facial expression mm.
- Innervated by CN VII (facial)
Deep Fascia Layers of the Neck
Deep to superficial fascia; dense, organized connective tissue layer, devoid of fat
- Envelops most body structures deep to skin & subcutaneous tissue
- Compartmentalizes structures of the neck
o Investing fascia
o Prevertebral fascia
o Carotid sheath, alar fascia
o Pretracheal fascia, buccopharyngeal fascia
Investing Fascia
Most superficial of deep fascia layers; encircles the entire neck
- Surrounds trapezius m. and SCM
- Superior and inferior terminations are the same as the trapezius and sternocleidomastoid m. attachments (clavicle)
Prevertebral Layer of Deep Cervical Fascia
Tubular sheath for prevertebral mm.
Contents: longus colli, longus capitius, scalenes, and deep cervical mm.
Attachments:
- Cranial base (superiorly)
- Endothoracic fascia (inferiorly)
- ALL at T3 (centrally)
- Axillary sheath that surrounds brachial plexus, axillary vessels, and cervical sympathetic trunk (laterally) *IMPORTANT if infection in the area, can affect surrounding plexus
Carotid sheath of Deep Cervical Fascia
Tubular fascia, extends from base of cranium to the root of the neck
Contents: common and internal carotid aa., IJV, CN X, some deep cervical lymph nodes, carotid sinus n., sympathetic nn.
Attachments:
- Blends with investing and pre-tracheal fascia (anteriorly)
- Blends with prevertebral layer of fascia (posteriorly)
- Cranial base (superiorly)
- Middle mediastinum of thorax (inferiorly)
Pretracheal fascia
Limited to anterior neck
Muscular part: encloses infrahyoid mm (in purple)
Visceral part: thyoids gland, trachea, esophagus (in blue)- continuous posteriorly and superiorly with buccopharyngeal fascia of pharynx (green)
Attachments: hyoid bone (superiorly), blends with fibrous pericardium of heart (inferiorly), continuous with carotid sheath (laterally)
Alar Fasia of Deep Cervical Fasia
Thin layer to prevertebral fascia, further subdivides retropharyngeal space
Attachments:
- Posterior side of buccopharygeal fascia (midline)
- Cranium (superiorly)
- Level of C7/T2 (inferiorly)
- Extends laterally and terminates in carotid sheath/prevertebral fascia
Retropharyngeal Space
Located posterior to buccopharyngeal fascia and anterior to alar fascia
- Permits movement of pharynx, esophagus, larynx, trachea relative to vertebral column during swallowing
Attachments:
- Cranial base (superiorly)
- Carotid sheath (laterally)
- Superior mediastinum (inferiorly, about T1,T2)
Prevertebral “Danger” Space
Between alar & prevertebral fascia
- Infections here can spread from skull base down into posterior mediastinum to the level of the diaphragm
- Nortorious for inferior spread of infections here
Posterior Cervical Triangle
Wraps around to lateral side of neck, contains platysma m.
Boundaries: posterior border of SCM (anterior), anterior border of Trapezius m. (posterior), middle 1/3 of clavicle (inferior), investing layer of deep cerical fascia (roof); splenius capitus, levator scapulae, middle and posterior scalene mm. covered by prevertebral fascia (floor)
Contents:
- Platysma m.
- Neurovasculature: EJV, cutaneous nn., Motor nn., transverse cervical & suprascapular aa.
- Deep muscles
Sternocleidomastoid m.
O: mastoid process
I: Sternal head: anterior surface of manubrium of sternum
Clavicular head: superior surface of medial 1/3 clavicle
Inn: Accessory n. (CN XI)
Action:
Unilateral: ipsilateral neck flexion & rotates superiorly to contralateral side
Bilaterally: extend neck, flex cervical vertebrae (bring chin to manubrium), extend superior and flex inferior cervical vertebrae (thrust chin forward with level head)
Assists in respiration (elevate manubrium and clavicle
Trapezius m.
O: midline
I: lateral 1/3 clavicle, acromion, spine of scapula
Inn: Accessory n. (CN XI)
Action: Descending part: elevates
Ascending part: depresses
Middle/all part together: retracts
Descending and ascending: rotate glenoid cavity superiorly
Posterior Triangle Contents
- Platysma m.
- Neurovasculature: EJV, cutaneous nn., Motor nn., transverse cervical & suprascapular aa.
- Deep muscles
Lesser Occipital Nerve
C2
Runs superiorly along posterior border of SCM, crosses over portion of occipital a.
- Supplies neck and scalp posterior to auricle
Greater auricular n.
C2-C3
Ascends vertically on surface of SCM, runs with EJV superiorly toward ear
– Supplies lobe & skin posterior to auricle
– Also supplies angle of mandible to mastoid process
Transverse Cervical N.
C2-C3
Runs transversely across middle of SCM
- Supplies skin of anterior cervical triangle & lateral neck
Supraclavicular nn.
C3-C4
Generally 3 main branches: medial, intermediate & lateral (post.) nn.
Run superficial to clavicle & deep to platysma
- Supply skin of clavicular region
Accessory N
CN XI
Emerges from jugula foreamen of skull, runs diagonally through triangle deep to investing fascia
- Supplies both SCM & trapezius mm.
Phrenic N.
C3-C5
Located deep to prevertebral fascia, descends vertically along anterior scalene m., crossed anteriorly by transverse cervical a. & suprascapular a.
- Enters thorax between subclavian v. & a.
- Travels along pericardial sac to supply diaphragm
Transverse Cervical and Suprascapular Arteries
- Both arise from the thyrocervical trunk
- Transverse cervical a. supplies trapezius m.
- Supplies rhomboid and levator scapulae mm. as dorsal scapular a.
- Suprascapular a. supplies supraspinatus and infraspinatus mm.
3 Scalene mm.
Inn: Ventral rami C3-C8 nn.
Action: Tilt neck laterally
Interscalene Triangle
Elongated triangle deep to posterior cerivcal trinagle
- Formed by anterior scalene, middle scalene & 1st rib
- Brachail prexus roots & subclaian a. pass through the triangle
- Subclavian v. passes anterior to anterior scalene m.
- Thoracic outlet syndomre can happen in this area (cancer, pregnancy), leading to compression to nerve and blood vessel
