B1W2: Shoulder Region Flashcards
Movements of the upper limb
flexion/extension abduction/adduction medial rotation/lateral rotation (along long axis of limb) protraction, retraction (shoulders) circumduction (combination of all!)
aponeuroses
flat sheets that anchor muscle to skeleton, deep fascia or other muscles
Origin and insertion of muscles
Origin stays put (proximal attachment), insertion moves (distal attachment)
Four types of muscles
Prime mover=agonist, main muscle for producing a specific movement of the body Fixator=steadies the proximal parts of a limb while movements are occuring in distal parts Synergist=helps/assist a prime mover Agonist=opposes action of a prime mover
Components of pectoral girdle
Clavicle and scapula
General attachments of pectoral girdle
Posteriorly, scapula has no bony connection with the spine Only one bony attachment that attaches the pectoral girdle to the upper limb, and that is the sternoclavicular joint
Role of pectoral girdle
Aids in protection, as shock absorber, base for muscles and an interface between the axial/appendicular skeletal components
protection for neurovascular structures
Vulnerability of clavicle
Vulnerable in the middle/lateral ttwo thirds; the shoulder drops if broken and limb sags because it protects the brachial plexus, axillary artery and vein If you fracture the clavicle, broken parts can move around
Role of clavicle in pectoral girdle
–muscle attachment (6)
–strut: holds upper limb away from trunk
–elevates/depresses at sternoclavicular side
–transfers weight of upper limb to trunk (fulcrum)
Attachment of clavicle to body (part of shoulder joint)–sternoclavicular joint
Sternoclavicular joint: joint that connects the sternal (medial) end of clavicle to the shallow end of the sternum(mandirbum); synovial joint; only bony one that connects upper limb to trunk
Has
–costoclavicular ligament connecting to first rib
–sternoclavicular ligament connecting to sternum
–fibrocartilage articular disks between it and sternum
Attachment of clavicle to body (part of shoulder joint)–Acromioclavicular joint
Acromion of scapula and acromial (lateral) end of clavicle; synovial joint
Has:
–articular disk
–coracoacromial ligament (acromion to corocoid process)
–acromioclavicular ligament (clavicle to acromion)
–coracoclavicular ligament (trapezoid and concoid ligaments moving medially; clavicle to coracoid process)
–superior transverse scapular ligament
Part of shoulder joint: glenohumeral joint
- Head of humerus to scapula
- Large articular surface on head of humerus and shallow articular cup on scapula; only articulation of humerus to pectoral girdle
- Glenoid fossa is the space humerus is trying to attach to
- Glenoid labrium tries to cover area for more surface area by deepening cup
- Humeral head held into glenoid fossa by Musculotendenous Rotator Cuff
- Coracohumeral and glenohumeral ligaments help stabilize
Part of shoulder joint: scapulothoracic joint
Gliding of scapula across back of pectoral cage (functional joint only) Causes: Elevation/depression Protraction/retraction Upward rotation/downward rotation
What is the role of the scapula?
attachment of 17 muscles
–three sets of attachments that connect it to clavicle; work together as a unit
–spine, acromion, coracoid process all help with muscle attachment
What can be damaged by the free ends of a broken clavicle?
–brachial plexus (brachialis artery and vein in limb)
Where would humerus be damaged?
Due to osteoporosis, it would detach and fall on forearm or simply break at the surgical neck
RADIAL NERVE is damaged
Components of rotator cuff
Subscapularis (anterior) Supraspinatus (above spine, posterior) Infraspinatus Teres minor Rather than being static ligaments, they help stabilize the humerus and still move! Can sense what it’s doing and contract accordingly
What is the scapulohumeral rhythm?
Abduction of the upper limb 30 degrees up, supraspinatus – initiate abduction 1:2 ratio between what happens with the scapula and what happens with humerus
What muscle is key to moving the scapula?
Serratus anterior
What would a downward blow to the shoulder region hurt? (The joint)
Acromialclavicular joint
Generalities of the innervation of the shoulder region (will go into more depth later)
Many muscles on dorsal side of the trunk but innervated by branches of the ventral primary rami
Pectoral girdle provides protection for neurovascular structures, like the axillary artery, and especially the brachial plexus
Serratus anterior structure/function
long thoracic nerve on surface –attaches scapula to ribs, so if nerve of this muscle was severed you would get winged scapula
Posterior/anterior axioappendicular groups of muscles
proximal attachment on trunk, distal attachment on pectoral girdle or humerus
Common rotator cuff injuries
tear, attrition due to aging –supraspinatus –most often damaged; most calcified, aged
