Lecture 17: pectoral girdle Flashcards
Name bones of pectoral girdle
Scapula
Clavicle
= 2 halves with a lot more mobility
Describe sternal end clavicle
Articulates with sternum
Describe Conoid tubercle clavicle
Points posteriorly
Describe shaft clavicle
Middle part, curved
Describe acromial end clavicle
Articulate with acromion
What is present on inferior surface clavicle
Groove for Subclavius muscle = defining feature of inferior surface
Which side of clavicle longer
Medially much longer
Laterally shorter
What does scapula articulate with
Clavicle and humerus
Describe scapula bone shape
Irregularly shaped flat bone ~triangular ish
What does scapula have
Fossae and borders = provides surfaces for muscle attachments
Name parts of scapula that serve as muscle attachment sites for shoulder muscles
Thick bony projections =
Spine, coracoid process, acromion, supra an infra glenoid tubercles
Describe borders of scapula
Superior border (top, next to coracoid process)
Lateral border = more straight, linear
Medial border = curved Ish, inside
Describe processes/projections of scapula
Coracoid process = like hook
Acromion (extension of spine)
Spine of scapula - med to lat
Describe fossae of scapula
Subscapular fossa = ant
Supraspinous fossa= post, above spine
Infraspinous fossa = post, below spine
Describe angles of scapula
Superior angle
Lateral angle - under acromion, articulates with head of humerus
Inferior angle - bottom of triangle
Describe important parts of lateral view scapula - tubercles/fossa
Supra glenoid tubercle
Glenoid fossa = shoulder joint facet
Infra genloid tubercle
Name the 4 joints of pectoral girdle
Acromioclavicular = post to ant, forms pectoral girdle
Sternoclavicular joint
Scapulothoracic joint - scapula + rib cage
Glenohumeral joint and subacromial space =genloid facet and numeral head
Joint type acromioclavicular joint
Synovial joint
Planar/gliding
But limited movement
Movements acromioclavicular joint
Almost no mobility
Due to presence of strong ligaments that link movement of scapula and clavicle on same side - so cannot move on own
Name the 3 ligaments of acromioclavicular joint
Acromioclavicular ligament
Coracoclavicular ligament
Coracoacromial ligament
Describe acromioclavicular ligament
Reinforces fibrous capsule - thickening of it
Describe coracoacromial ligament
Links 2 parts of same bone
Stars and ends on same bone =
Provides stability to roof of glenohumeral joint
Describe coracoclavicular ligament
Strongest!!!!
Made up of trapezoid ligament and conoid ligament (attaches to conoid tubercle)
What does acromioclavicular joint Do
Synchronizes scapula and clavicle
Describe joint type sternoclavicular joint
Synovial joint - complex
Between clavicle (sternal end), manubrium and first costal cartilage
Saddle - biaxial geometry = articular surfaces are concave along one axis and convex along other = baxial
Movements sternoclavicular joint
Protraction/retraction
Elevation/depression
What is scapulothoracic joint
Not an anatomical joint = no synovial capsule, cartilage or ligaments
But it is a physiological joint = permits motion of bones without features of synovial joints
Describe joint region scapulothoracic joint
Anterior surface of scapula (subscapular surface) against posterior surface ribs 2-7
Descrive muscles scapulothoracic joint
Subscapualris and serrratus anterior
With lose ct between to facilitate gliding
(Lay against each other - muscle to muscle)
Describe function scapulothoracic joint
Enables scapular motion
Integrates pectoral girdle with shoulder joint (scapula + humerus) = increase rom of shoulder complex
(Scapulothoracic with glenohumeral, = so can reach higher)
Describe movements of pectoral girdle at scapulothoracic joint
Elevation/depression
Protraction (abduction)/retraction (addiction)
Upwards/downwards rotation (adds extra rom to shoulder)
Where does most movement at scapulothoracic joint occur - explains
Most of movement actually happens at sternoclavicular joint bc of strong ligaments that link scapula and clavicle and the relatively immobile acromioclavicular joint
* motion needs to happen at actual synovial joint = sternoclavicular joint
Name anterior muscles of scapulothoracic joint
Subclavius
Pectoralis minor
Pectoralis minor attachments
Anterior ribs 3-5 to coracoid process of scapula
Pectoralis minor functions
Depresses, protracts and rotates scapula inferiorly (downwards rotation)
Pectoralis minor Innervation
Medial pectoral nerve c8-t1
Subclavius attachments
(Under clavicle)
From 1st rib (manubrium) to inferior surface of Clavicle (groove)
Subclavius Actions
Depress clavicle
Stabilizes sternoclavicular joint
Subclavius Innervation
Subclavian nerve c5-6
Where are Subclavius and Pectoralis minor
Deep to Pectoralis major
Name lateral muscles of scapulothoracic joint
Serratus anterior (boxers muscle)
Serratus anterior attachments
From lateral surface of ribs 1-9 to (fibres converge) medial/anterior border of scapula (medial edge subscapular fossa)
Serratus anterior Function
Primary protractor of scapula = strongest protractor
(Creates scapulothoracic joint)
Serratus anterior Innervation
Long thoracic nerve c5-7
Clinical correlate Serratus anterior
Weakness or paralysis of Serratus anterior (like injury to long thoracic nerve) = leads to weakness in scapular protraction - when pushing against wall = seen as winged scapula on affected side
= Serratus anterior cannot resist wall, retraction force from wall causes winged scapula
Name muscles of pectoral girdle - posterior
Trapezius
Levator scapulae
Rhomboid major and minor
Latissimius dorsi
Trapezius attachments
Skull and vertebrae c7-t12 to spine and acromion of scapula and lateral 1/3 of clavicle
Trapezius Actions
Functionally = 3 parts with diff orientations
Upper 1/3 = elevation (shrug), upwards rotation
Middle 1/3 (or all parts) = retraction *recruiting all 3 also produces pure retraction
Lower 1/3 = depression, upwards rotation (bc of configuartion of spine of scpaula and scapulothoracic joint = so upwards)
Trapezius Innervation
Accessory spinal nerve
Levator scapulae attachments
From cervical vertebrae to superior angle scapula
Levator scapulae Actions on scapula
Elevation
Some retraction
Levator scapulae Innervation
C3-5
Rhomboid major and minor attachments
Cervical and thoracic spine to medial border of scapula (deep to trapezius)
Rhomboid major and minor Actions
Retraction and some elevation
Downwards rotation (rhomboid major)
Rhomboid major and minor Innervation
Dorsal scapular nerve c5
Latissimus dorsi attachments
From lower thoracic vertebrae, tlf, ilium (pelvis) to intertubercular groove humerus
Latissimus dorsi Functions
Primarily a shoulder joint muscle
but also crosses scapulothoracic joint = moves scapula too = downwards rotation, some retraction And depression
Latissimus dorsi Innervation
Thoracodorsal nerve c6-c8
