The Pectoral Girdle Flashcards
The Pectoral Girdle consists of?
The clavicle and scapula
What joint links the free limb to the axial skeleton?
The sternocalvicular joint
Why are muscles required to stabilise the shoulder joint?
Because as the shoulder joint is extremely mobile, it has sacrificed stability, which needs to be overcome with muscles
How are movements in the pectoral girdle classified?
By the movement of the scapula
Superior rotation
Glenoid points superiorly
Whats another name for the forearm?
‘Anti-brachium’
Clavicle functions?
- To act as a strut to stop muscles attached to the scapula pulling it into the thorax.
- acts as an attachment point for muscles
Where is the weak point of the clavicle?
2/3 medially, 1/3 laterally. Here there is no muscles attached, so force of the free limb is transmitted to this area, making in a common place of breaking
The two roughened areas of the clavicle are, and what is their purpose?
1) Coracoclavicular area
2) Costoclavicular area
This allows for attachments of two ligaments that stabilise the clavicle
What is the purpose of having a mobile scapula?
For the hands. These need to be extremely sensitive and mobile with the environment
What are the borders of the scapula?
Medial, lateral and superior
What processes of the scapula are?
spinous, acromion and coracoid
What are the four fossas of the scapula?
Subscapula, supraspinous, infraspinous and glenoid
There is a groove in the middle of the clavicle, what is this called and what is it for?
Subclavian groove, for the subclavian muscle to run through
What does the clavicle articulate with?
The acromion process of the scapula, and the manubrium of the sternum
What are the four important joints of the pectoral girdle?
1) Sternoclavicular (synovial)
2) Acromioclavicular (synovial)
3) Shoulder joint
4) Scapula-thoracic (conceptual)
scapulothoracic joint
scapulothoracic join conceptual joint where scapula moves along the thoracic wall
What are the main stabilisers of the Sternoclavicular joint?
Anterior and posterior sternoclavicular ligaments
costoclavicular ligament
interclavicular ligament
Is posterior or anterior sternoclavicular ligament stronger?
Posterior is significantly stronger as there is a need to protect the posterior arteries that run behind the clavicle
Purpose of interclavicular ligament
Runs along the jugular notch, that supports the superior aspect of the SC joint. This is the only joint between the two sides, and means that the SC joints can’t be seperated
O and I of subclavius muscle. Purpose
O= first rib and costicartilage
I= subclavian groove
Acts as a brace to oppose any upwards tension of on the clavicle
What supports the inferior part of the clavicle?
The costoclavicular ligament
Main stabilisers of the acromioclavicular joint?
acromioclavicular ligament Coracoclavicular ligament (conoid + trapezoid)
What is special about the coracoclavicular ligament of the acromioclavicular joint?
Muscles like trapezoid attach and pull clavicle upwards. The CC ligament apposes this, and allows for the limb to be passively hanging with low energy expenditure
What is the purpose of ‘stabilising muscles’?
When stimulated, these muscles do not move but inside contract to stabilise the joint. this is especially important for highly mobile joints
Trapezius
O? I? Nerve? Action?
O= skull -T12 I= anatomical horseshoe Nerve= accessory nerve Action= retracts, elevates and depresses scapula
Levator Scapulae
O? I? Nerve? Action?
O= transverse process of upper cervical I= superior angle of scapula Nerve= dorsal scapula nerve Action= elevate and internally rotates scapula
Rhomboid Min & Maj
O? I? Nerve? Action?
O= spinous process I= medial border of scapula Nerve= dorsal scapula nerve Action= retracts, elevates and inferiorly rotates scapula can act as a stabiliser.
Latissimus Dorsi
O? I? Nerve? Action?
O= T7 - sacrum I= anterior humerus Nerve= Thoracodorsal nerve Action= adducts, internally rotates humerus
Pectoralis Major
O=
I=
O= clavicular and sternocostal I= anterior humerus Nerve= lateral and medial pectoral nerve Action= Adducts and internally rotates humerus
Pectoralis minor
O? I? Nerve? Action?
O= ribs (3-5) I= coracoid Nerve= medial pectoral nerve Action= depresses and protracts scapula
What is a good landmark of pec minor and pecmajor
The medial pectoral nerve runs through pec minor (innervates it) to pec major. therefore this connecting nerve can be a useful landmark
What is saturday night palsy?
When you full asleep with your arm full abducted, the neurovascular bundle is stretched and compressed under the coracoid process. This can cause numbness in the morning.
What part of Pectoralis Major is often damaged?
The sternocostal head. with excessive load, (excessive gymming) this can rupture.
Serratus anterior
O? I? Nerve? Action?
O= lateral anterior surface of ribs
I=medialborder of scapula
Nerve= Long thoracic nerve
Action= Protracts, depresses (and some lower fibres sup rotate) scapula
What is clinically important about the long thoracic nerve (supples serratus anterior)
It runs along top of serratus, with a axillary lymph node. during a maesectomy, you can damage this nerve, leading to a winged scapula.
