1)Osteology and Arthrology Pectoral Girdle Flashcards
What makes up the pectoral girdle
The clavicle and scapula
Sternonavicular joint and Acromionavicular joint= Pectoral Girdle
This allows transmission of the weight of the upper limb to the axial skeleton, and facilitating a wide range of movement of the upper limb.
Articulations of the shoulder complex
▪️STERNOCLAVICULAR JOINT- clavicle articulates with the
thorax
▪️ACROMIOCLAVICULAR JOINT- scapula articulates with the clavicle
▪️GLENOHUMERAL JOINT- scapula articulates with proximal humerus
Importance of the arrangement of the 3 joints that make the shoulder complex
This arrangement ensures that clavicular movements at the sternoclavicular and acromioclavicular joints are always associated with movements of the scapula and, movements of the scapula are often accompanied by movements of the humerus at the glenohumeral joint.
This enables the weight of the upper limb to pass from the humerus to the scapula, from the scapula through to the clavicle, and finally from the clavicle to the trunk at the sternoclavicular joint.
Sternoclavicular Joint
This joint provides the only direct connection between the pectoral girdle, upper limb and the trunk.
Sternoclavicular joint classification and nerve supply
synovial,saddle, complex, multiaxail
functionally similar to a ball and socket
Medial supraclavicular nerve C3,4
Subclavius C5,6
Sternoclavicular joint
Articular surface
See file
Sternoclavicular joint
Joint capsule
A fibrous capsule surrounds joint like a sleeve v strong.
Strengthened …….
▪️anteriorly-Ant sternoclavicular lig
▪️posteriorly -Post sternoclavicular lig
▪️superiorly- capsular thickenings
▪️Inferiorly = weaker
Attachments:
Both the clavicle and the sternum inferior part passing between the clavicle and upper surface of the first costal cartilage
Sternoclavicular joint
Synovial membrane
Complete intra-articular fibrocartilaginous disc divides joint into 2 separate cavities = 2 synovial membranes
Loose lateral membrane lines the capsule, reflected from articulator margin of medial end of clavicle to margins of intra-articular disc
Medial membrane attaches to articular margins on sternum and margins of intra-articulating disc.
Sternoclavicular joint
Intra-articular structures
intra-articular fibrocartilaginous disc
Complete intra-articular fibrocartilaginous disc divides joint into 2 separate cavities
Disc is flat round and thinner centrally, perforated allows communication between cavities.
Attachments:
It’s circumference to the joint capsule particularly anteriorly and posteriorly firmly attached superiorly and posteriorly to the upper border of the medial end of the clavicle and inferiorly to the first costal cartilage.
Sternoclavicular joint
Intra-articular structures
intra-articular fibrocartilaginous disc function
- Shock absorber= provides cushioning between the articular surfaces due to its histological structure = allows distortion of disc
- compensates incongruity of opposing articular surfaces which are not reciprocal
- Strong static stabiliser anchors clavicle to manubrium and 1st CC through direct attachment = Prevents medial displacement (elevation of the clavicle at medial end)
- Facilitates increased range of movement by dividing the joint cavity into 2 separate compartments
Sternoclavicular joint
Ligaments
- Anterior sternoclavicular ligament
- Posterior sternoclavicular ligament
- Interclavicular ligament
4.Extra Caspular:
Accessory ligament = costoclavicular ligament
Anterior sternoclavicular ligament
Strong broad fibres strengthened tendon sternomastoid
Attachments:
Superior and anterior part of medial end of clavicle
obliquely inferiorly medially
front of upper part of manubrium sterni
Posterior sternoclavicular ligament
Not as strong as anterior ligament. Broad. Strengthened by sternohyoid.
Attachments:
Laterally-Superior posterior part of medial end of the clavicle
Medially-back of upper part of the manubrium sterni
Interclavicular ligament
Attachments:
Upper aspect of sternal end of one clavicle passing across the jugular notch to join fibres from opposite side.
Some attach to jugular notch floor
costoclavicular ligament
Accessory ligament. Extra caspular
*Extremely strong ligament short dense fibres
Attachments:
Upper surface first costal cartilage lateral end to posterior aspect inferior surface medial end of clavicle
costoclavicular ligament laminate
Has 2 laminea separated by a bursa attaches to ant and post lips clavicular rhomboid impression.
Anterior fibres- superolaterally
Posterior fibres- superomedially
*cruciate arrangement
Limits elevation, anterior, posterior movement of clavicle excessive
Stability
Ant sternoclavicular
Post sternonavicular
Interclavicular
Costonavicular
Acromioclavicular Joint
This joint connects the lateral end of the clavicle and the acromion process of the scapula.
Role in movement of pectoral glide= greater than sternoclavicular (sagittal plane)
Acromioclavicular Joint
Classification and nerve supply
Synovial, Plane,complex,multiaxail
Lateral supraclavicular
Lateral pectoral
Supracaspular
Axillary nerves
C4,5,6
Acromioclavicular Joint
Articular surface
See file
Acromioclavicular Joint
Fibrous capsule
Relatively loose strong fibrous capsule surrounding joint. Thickest superiorly
Strengthened…….
▪️superiorly- reinforced fibres of trapezius
Joint margins of clavical and acromion = acromionavicular
Attachment:
Articular margins fibres run in parallel fasciculi from clavical to acromion
Acromioclavicular Joint
Synovial membrane
Lines the inner surface of capsule attaching margins of articular surfaces
Acromioclavicular Joint
Intra-articular surfaces
The wedge shape fibrocartilaginous intra-articular disc divides cavity
Joint disc is attached to upper inner part capsule extending down between the two articulating surfaces
Compensates small degree of incongruity between 2 joint surfaces
Acromioclavicular Joint
Coracoclavicular ligament
Extremely powerful situated medial to the acromioclavicular joint and anchoring lateral end of clavicle to the coracoid process
The coracoclavicular ligament consists of 2 distinct bands of fibres:
- The trapezoid fibres lie anterolaterally and are attached inferiorly to a roughened ridge on the superior surface of the coracoid process, passing obliquely to attach to the trapezoid line on the inferior surface of the clavicle.
- The conoid fibres lie posteromedially, attaching from the “elbow” of the coracoid process, passing vertically upwards to attach to the conoid tubercle on the inferior surface of the clavicle.
* Due to their position and orientation, the two parts of the coracoclavicular ligament are arranged to restrain opposite movements of the scapula with respect to the clavicle.
Stability
Coraconavicular ligament
Factors responsible for limiting range of movement of pectoral girdle
Elevation
SCJ: Tension in costoclavicular ligs & subclavius
ACJ: Coracoclavicular lig (both bands)
Factors responsible for limiting range of movement of pectoral girdle
Depression
SCJ: Interclavicular lig. & intra-articular disc
Factors responsible for limiting range of movement of pectoral girdle
Protraction
SCJ: Sternoclavicular ligament & costoclavicular ligament
ACJ: Coracoclavicular ligament & fibrous capsule
Factors responsible for limiting range of movement of pectoral girdle
Retraction
SCJ: Sternoclavicular ligament & costoclavicular ligament
ACJ: Coracoclavicular ligament & fibrous capsule
Function of the clavicle
- Acts as a stronghold in the upper limb away from trunk
- Transmits force from the upper limb to the axial skeleton
- attachment for ligaments
- attachment for muscles
- Facilitates wide range of movement of the upper limb
What is the roof of the subacromial space made of
Fibro-osseous structure:
coracoacromial arch
coracoid + acromion processes + coracoacromial ligament
What is the floor of the subacromial space made of
Humeral head
Superior aspect of fibrous capsule
What anatomical structures lie within the subacromial space
Subacromial bursa
Supraspinatus tendon
Infraspinatus tendon
Long head of biceps tendon
