Flashcards in Shoulder/Arm Anatomy Deck (190)
What are the factors that affect the amount of force a muscle exerts at a joint axis?
Size/Bulk of a muscle (Cross-sectional area)
Shape of a muscle: straight or penate or something
angle of pull relative to the axis
Insertion site close to or far away from joint
What is a straight muscle good for? What is a penate or bipenate muscle good for?
Straight Muscle: great ability to change in length
Bipenate or penate muscle: supplies more power, less ROM
When a muscle is attached close to the joint...it is good for? When it is attached far away?
Close to the joint: speed
Far from the joint: power
All muscles help to stabilize the joint they _____.
the joint they cross
In general, the upper extremity is good for speed/power & the lower extremity is good for speed/power.
Upper Extremity: Speed
Lower Extremity: Power
What are the 3 things you must ask yourself when you look at a new muscle?
What are the axes this muscle exhibits? What are its possible actions? Where does the muscle cross the joint relative to the axis?
Describe how the upper limb is stabilized.
What is crazy about the upper limb is that the only bone attachment to the axial skeleton/stabilization is the sternoclavicular joint. The rest is just muscle stabilization. This is why it is so freely moveable.
Why is it important that the inferior angle of the scapula can move laterally & medially?
b/c this allows for full abduction of the scapula.
What is the shape of the clavicle? What is the superior side like? What is the inferior side like?
Superior side is smooth
Inferior side is rough so that ligaments can attach to it.
T/F The clavicle is a common bone to fracture.
What is the origin of the clavicle?
What are 2 fun bone facts of the clavicle?
1. first long bone to ossify: weeks 5-6
2. last long bone to fuse @ epiphyseal plate around 25 years
How does the clavicle ossify?
a little endochondral ossification maybe
What are the 2 joints that the clavicle is a part of?
What are 2 possible actions of the shoulder girdle?
shoulder shrug: elevation/depression
Protraction/Retraction (along the vertical axis)
During protraction/retraction of the scapula...what must happen to the scapula?
It must glides along the chest wall with 15 degrees worth of gliding movement
Movements of the shoulder girdle require some mobility of the ____ joint.
Which ligaments stabilize the acromioclavicular joint (AC)?
Mainly: coracoclavicular ligaments
Maybe sorta: coracoacromial ligament
What are the 2 ligaments that make up the coracoclavicular ligaments? Where are they located?
trapezoid ligament (more lateral)
conoid ligament (more medial)
What is the function of the coracoacromial ligament?
it forms the roof of the glenohumeral joint-->this is where the head of the humerus rests!!
Where does the clavicle usu fracture?
usu in the middle & distal 3rd
**usu just proximal to the coracoclavicular ligaments
What is the difference b/w shoulder separation & shoulder dislocation?
shoulder separation: occurs at the AC joint
shoulder dislocation: occurs @ the glenohumeral jt
T/F You cannot separate the AC joint w/o tearing the coracoclavicular ligaments, as they are a strong stabilizing force.
FALSE. You can separate the AC jt w/o tearing the ligaments. It consists of just a broken clavicle, distal to the ligaments.
Often though, you break the clavicle & tear the ligaments.
Describe shoulder dislocation.
the head of the humerus is forced out of the glenoid fossa
What direction is the head of the humerus usu pushed in when you experience a shoulder dislocation?
usu anteriorly & inferiorly.
Describe a physical position that would make it easier to dislocate your shoulder. Why is this such a vulnerable position?
when your arms are fully abducted above your head...if someone came from behind & smacked your shoulder.
vulnerable b/c the head of the humerus in this position isn't in contact w/ the glenoid fossa...when articular surfaces aren't touching called a loose packed jt & is more vulnerable...once it is dislocated...muscles contract, forcing the head of humerus into the axillary fossa.
What is the glenoid labrum & how does it relate to shoulder dislocation?
this is an extension of cartilage that is found in the shoulder. It is easy to tear during shoulder dislocation.
How can you put a shoulder back into its socket after shoulder dislocation?
if you have had multiple dislocations, maybe you can just pop it back...usu need muscle relaxants & a doctor's assistance.
Describe the sternoclavicular joint.
It is a synovial joint w/ 2 synovial cavities and a fibrocartilage articular disc.