Shoulder and Brachial Plexus Flashcards
Pectoral girdle
An incomplete bony ring.
- Formed by the manubrium, clavicles, and scapulae, provides attachments and mobility
Intrinsic muscles: Deltoid
thick powerful muscle that forms the contour, clavicular, acromial, and
spinal, when all 3 parts contracts
simultaneously: abduction
Intrinsic muscles: Teres major
Lies on the inferolateral 1/3 of
scapula, adducts and medially rotates the
humerus; stabilizing humeral head
SITS muscles
Supraspinatus: assists the deltoid with arm abduction.
Infraspinatus: laterally rotates arm.
Teres minor: laterally rotates arm.
Subscapularis: medially rotates and adducts arm
Glenohumeral joint
ball and socket joint, articulation between the large humeral head and shallow glenoid cavity, inferior part not reinforced by SITS and is the weakest
GJ ligaments
Glenohumeral ligaments on the internal aspect of the capsule strengthen it anteriorly.
Coracohumeral ligament reinforces
the capsule superiorly.
Coraco-acromial ligament prevents the superior displacement of the humeral head
Synovial bursae
(subacromial, subscapular) provide cushioning and reduce friction between bones, tendons, and muscles around joint
GJ movements
Abductors: deltoid, supraspinatus
Adductors: teres major, latissimus dorsi, pectoralis major
GJ upward and downard rotators
upward: descending and ascending portions of trapezius, serratus anterior, abduction
downward: rhomboids, levator scapulae, latissimus dorsi, pectoralis minor, adduction
Scapula retractors and protractors
Retractors: middle part of trapezius, rhomboids, latissimus dorsi (indirectly)
Protractors: serratus anterior, pectoralis minor
Brachial plexus
Formed by the union of ventral rami of spinal nerves C5-T1 that constitute the roots, inferior part of the neck, the roots unite to form three trunks (superior C5-C6, middle C7, inferior C8-T1), anterior divisions supply the flexor compartment, posterior divisions supply extensor compartment
Brachial cords
- Anterior + Superior + Middle trunks = lateral cord
- anterior division of inferior trunk = medial cord
- Posterior divisions of all 3 trunks unite to form posterior cord
Clavicles
supraclavicular (arising from the roots and trunks)
infraclavicular (arising from the cords) parts by the clavicle
Superclavicular branches
- dorsal scapular n. (to rhomboids)
- suprascapular n. (to supra- + infraspinatus muscles)
- subclavian n. (to subclavius)
- long thoracic n. (to serratus anterior)
Infraclavicular branches
- lateral pectoral n. (to pectoralis major)
- medial pectoral n. (to pectoralis minor and major)
- medial cutaneous nerve of arm
- medial cutaneous nerve of forearm
- upper subscapular n. (to subscapularis)
- thoracodorsal n. (to latissimus dorsi)
- lower subscapular n. (to subscapularis and teres major)
