posterior triangle Flashcards
the anterior and posterior triangles are separated by the ?
sternocleidomastoid
boundaries of posterior triangle
anterior: posterior border of SCM
posterior: anterior border of trap
inferior: middle 1/3 of clavicle
apex: where SCM meets the trap on superio nuchal line
inferior belly of omohyoid divides posterior triangle into 2 triangles
- occipital: occipital artery and spinal accessory
- subclavian or supraclavicular: contains subclavian vessels and lower end of EJV
roof of posterior triangle contains
terminal branches of cervical plexus, external jugular vein, and superficial cervical lymph nodes
floor of posterior triangle contains
semispinalis capitis
splenius capitis
levator scapulae
scalene mass: scalene posterior, scaleneus medius
what are the muscles of the floor of posterior triangle covered by?
prevertebral layer of deep cervical fascia
scalene muscles are hidden under?
SCM
nerves of posterior triangle
- spinal accessory
- roots of cervical plexus (C1-C4) and its branches
- roots (C5-T1) and trunks of brachial plexus
arteries of posterior triangle
- subclavian (3rd part)
- branches from thyrocervical trunk: suprascapular and transverse cervical arteries
- dorsal scapular (branch of 3rd part)
veins of posterior triangle
subclavian
lower end of external jugular vein
muscle of posterior triangle
inferior belly of omohyoid
contents of posterior triangle
- great auriculuar nerve
- lesser occipital nerve
- spinal acc
- phrenic nerve
- transverse cervical artery
- brachial plexus
- suprascapular artery
- subclavian artery
- subclavian vein
- thyrocervical trunk
- inferior thyroid artery
- ansa cervicalis
what nerve goes through the trapezius?
spinal accessory
what makes up the ansa cervicalis?
descendense hypoglossi (from C1 motor) and descendens cervicalis (from C2)
the lesser occipital nerve and great auricular nerve turn into
transverse cervical
supraclavicular nerve comes from?
C3
C3, C4, C5 turn into
phrenic nerve above scalene anterior muscle
cutaneous branch of cervical plexus
- great auricular (C2-3): supplies skin over parotid gland and behind the auricle and over angle of jaw
- lesser occipital nerve (C2): supplies the scalp behind and above the ear
- transverse cervical nerve (C2-3): crosses SCM to anterior triangle. Supplies skin of the front of neck
- supraclavicular nerve (C3-4): divides into lateral, intermediate, and medial branches. Supplies the skin of the front of thoracic wall and shoulder
motor branch of cervical plexus
- superior root of ansa cervicalis (C1, descendens hypoglossi)
- inferior root of ansa cervicalis (C2 & 3, descendens cervicalis)
- phrenic nerve (mainly C4 with contribution from C3 and C5), descends anterior to scalenes anterior muscle and supplies diaphragm
- deep motor branches to prevertebral muscles and shoulder muscles
spinal accessory nerve
- passes deep to SCM
- supplies SCM before entering junction of upper and middle 1/3 of SCM
- crosses posterior triangle in or below the investing layer of deep fascia and parallel to levator scapula
- disappears under trap at junction bw upper 2/3 and lower 1/3
- supplies SCM and trap
parts of accessory nerve
cranial part–jugular
accessory part–magnum (IX, X, XI)
isolated spinal sccessory mononeuropathy (SAM)
iatrogenic complication of surgery in posterior triangle
-symptoms: weakness of trap; SCM involved sometimes
brachial plexus
- network of nerves supplying upper limb
- composed of ventral rami of lower four (C5-C8) cervical and first thoracic spinal nerves (T1)
- divided by clavicle into supraclavicuar and infraclavicular parts
brachial plexus roots to trunks
upper: C5–C6
middle: C7
lower: C8-T1
trunks to divisions of brachial plexus
upper: anterior, post
middle: anterior, post
lower: anterior, post
divisions to cords of brachial plexus
posterior to posterior cord post
lateral cord to anterior division of upper and middle trunk
medial cord–anterior divistion of lower trunk
branches of brachial plexus from roots
- nerve to serratus muscle from C5-C7
- nerve to rhomboid (dorsal scapular nerve) from C5
- phrenic nerve from C5
branches of brachial plexus from trunks
nerve to subclavius and suprascapular nerves from upper trunk
branches of brachial plexus from lateral cord
- musculocutaneous nerve
- lateral pectoral nerve
- lateral root of median nerve
branches from medial cord
ulnar nerve medial root of median nerve medial pectoral nerve medial cutaneous nerve of arm medial cutaneous nerve of forearm
branches from posterior cord
upper and lower subscapular nerves
thoracodorsal nerve (to latissmus dorsi)
axillary and radial nerves
erb-duchenne upper trunk palsy
- paralysis of upper trunk of brachial plexus (C5-C6)
- porter’s tip hand
dejerine-klumpke lower trunk palsy
paralysis of lower trunk of brachial plexus (C8-T1)
-causes paralysis of intrinsic muscles of the hand causing Claw Hand
four types of brachial plexus injuries
- avulsion: most severe– nerve torn from spine
- rupture: nerve torn but not at spinal attachment
- neuroma: nerve torn and healed but scar tissue pressures on injured nerve and prevents it from conducting signals to muscle
- neuropraxia or stretch : nerve damaged but not torn**most common
the right subclavian artery comes as a —– while the left comes as a —-
right comes from brachiocephalic artery
left comes from branches
origin of subclavian artery
RT: brachiocephalic
left: aorta
termination of subclavian artery
at outer border of first rib as axillary artery
1st part of subclavian branches into?
- vertebral artery
- internal thoracic (mammary) artery (breast and thoracic wall)
- thyrocervical trunk that gives 3 branches: inferior thyroid, transverse cervical, suprascapular
2nd part (deep to sc. anterior) of subclavian
costocervical trunk that gives superior intercostal and deep cervical branches
from 3rd part of subclavian (lateral to Sc. anterior)
dorsal scapular artery
