Origin
· 2 heads
· rounded tendon from manubrium
· fleshy muscle from clavicle
· triangular interval between them
· internal jugular vein lies there
Path
· separates anterior and posterior triangles
· beneath it lies
· cervical plexus in upper half
· carotid sheath in lower half
· enclosed by splitting of deep fascia
Insertion
· manubrial head
· from tip of mastoid
· to superior nuchal line
· clavicular head
· superior nuchal line medial to manubrial fibres
· deep part to mastoid
· accessory nerve passes between it and other 3 parts
Nerve supply
· spinal part of accessory nerve
· esp. C2,3
· innervated by cortex of same side
· when looking to left, right muscle contracts
· borders
· sternomastoid
· trapezius
· apex
· back of skull on superior nuchal line
· base
· middle third of clavicle
· roof
· deep fascia
· floor
· prevertebral fascia
· beneath prevertebral fascia
· splenius, levator scapulae, scalenes
· subclavian artery
· brachial plexus
· cervical plexus
· emerges at posterior border of sternomastoid
· at junction of upper and middle thirds
· passes vertically over levator scapulae
· disappears beneath anterior border of trapezius
· 5 cm above clavicle
· crosses lower medial part
· transverse cervical and suprascapular arteries
· just above clavicle
· subclavian artery
· 3rd part
· at lower border of triangle
· external jugular vein
· at anterior border of triangle
· cutaneous branches
· plexus itself not in triangle
· formed by loops between anterior rami of C1-4
· lies on scalenius medius
· deep to prevertebral fascia
· covered by upper part of sternomastoid
Segmental
· to prevertebral muscles
Hypoglossal
· loop from C1
Muscular
· proprioceptive fibres
· from C2,3 to SCM
· from C3,4 to trapezius
Inferior root of ansa cervicalis
· formed from branch of C2 and C3
Phrenic nerve
· formed from C4 (and some C3 and C5)
Lesser occipital nerve
· C2
· hooks around accessory nerve
· runs up posterior border of SCM
· supplies posterolateral neck
Great auricular nerve
· C2
· passes vertically upwards over SCM
· supplies ear and face
· to neck
· not part of cervical plexus
Greater occipital
· posterior ramus of C2
· supplies back of neck
Third occipital
· posterior ramus of C3
· supplies cylindrical part of neck
Fourth occipital
· posterior ramus of C4
· supplies cape distribution
· digastric
· stylohyoid
· mylohyoid
· geniohyoid
· sternohyoid
· omohyoid
· thyrohyoid
· sternothyroid
Omohyoid
· superior belly attached to lateral part of inferior border of hyoid
· passes beneath SCM
· lies over carotid sheath
· becomes tendon where lies over internal jugular vein
· changes direction
· bound to clavicle by fascial sling
· derived from deep fascia
· inferior belly passes to transverse scapular ligament
Superior thyroid artery
· branch of external carotid artery
· pierces pretracheal fascia
· passes to upper pole
· external laryngeal nerve behind it
Inferior thyroid artery
· branch of thyrocervical trunk
· pierces pretracheal fascia
· passes to lower pole
· recurrent laryngeal nerve nearby
Superior thyroid vein
· follows superior thyroid artery
· enters internal jugular or facial vein
Middle thyroid vein
· passes from middle of lobe
· enters internal jugular vein
Inferior thyroid vein
· forms plexus
· drains into brachiocephalic veins
Recurrent laryngeal nerves
· run in groove between trachea and oesophagus
· together with inferior thyroid artery
External laryngeal nerves
· run behind superior thyroid artery
· arises from
· arch of aorta on left
· brachiocephalic on right
· lies in medial part of carotid sheath
· gives off no branches
· bifurcates at C3
· at tip of hyoid
· into external and internal carotids
External carotid artery
· commences at C3
· passes deep to posterior belly of digastric
· enters parotid
· divides into
· maxillary artery
· superficial temporal artery
· gives off 6 branches
· superior thyroid
· lingual
· facial
· occipital
· posterior auricular
· ascending pharyngeal
Internal carotid artery
· commences at C3
· starts lateral to external carotid
· slopes posteriorly to lie medial
· no branches in neck
· emerges from jugular foramen
· lies on lateral side of carotid sheath
· joins subclavian to form brachiocephalic vein
· commences beneath chin
· passes downward under platysma
· pierces deep fascia
· lies above sternum
· passes laterally deep to SCM
· enters external jugular vein
· courses down in front of sternomastoid
· pierces deep fascia 2 cm above midpoint of clavicle
· empties into subclavian vein
· lies on front of internal jugular vein
· formed by union of
· superior root from hypoglossal nerve
· inferior root from C2 and C3 anterior rami