Scapula and Clavicle - Shoulder Girdle

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Transcription

This is a tutorial on the shoulder girdle. The shoulder girdle consists of the scapula at the back and the clavicle anteriorly. The shoulder girdle is also referred to as the pectoral girdle. Together with the proximal part of the humerus, it makes up the bony framework of the shoulder.   In this tutorial, I’ll talk about some aspects of the shoulder girdle.   We’ll talk about the clavicle and the scapula.

The clavicle is this long bone here which connects the scapula at one end and the manubrium of the sternum at the other end.   It medially articulates with the manubrium and laterally, it articulates with the scapula at the acromion process.

 

Just looking at it from this superior view, you can see the curve shape, this sort of s-shape of the bone. It’s convex medially just before it articulates with the manubrium of the sternum. That’s the clavicle.

 

Also, another thing to point out, on the underside of the clavicle, you’ve got a little tubercle at the lateral end called the conoid tubercle, which I don’t think is very clear on this model.

 

This is lateral, this is medial. We’re looking at the underside of the clavicle. I’ll just show you back that we’re looking at it from an inferior view, I just rotated it around and I’ve taken away the other bones and we’re now looking at the inferior surface.   Approximately here, you have this little bony outgrowth called the conoid tubercle where the coracoclavicular ligament attaches.

 

The coracoclavicular ligament attaches the coracoid process (so the coraco- part of that word) to the clavicle, so coraco+clavicular. It runs from here to here. The coracoid process is this bony outgrowth of the scapula, which I’ll come on to talk about in a minute, but just be aware of this conoid tubercle on the underside of the clavicle.

 

Just rotating around, we’ll take a look at the scapula now. The scapula is this flat bone that sits on the back. It serves as the point of attachment for many muscles. You’ve got two angles. You’ve got the superior angle at the top and an inferior angle here at the bottom. You’ve got three borders, a medial border, a lateral border and a superior border.

 

And you’ve got three processes. You’ve got this spine of the scapula, the spinous process. You’ve got the acromion process, this process here which articulates with the clavicle (the acromion process). And then you’ve got the coracoid process, which I’ve just talked about, so this little hook-shaped bone which extends the glenoid fossa, which articulates with the humerus.

 

Three processes – spinous process, acromion process (which articulates with the clavicle, this thing here) and then you’ve got this hook-shaped process, which extends outwards.

 

You’ve also got two surfaces of the scapula. You’ve got the posterior surface and the anterior surface. The anterior surface is the costal surface which lies against the ribs. The anterior surface, the costal surface lies against the ribs and the posterior surface, which is obviously at the back of the scapula.

 

The posterior surface of the scapula is divided by this spinous process into two halves. You’ve got the superior half, which you’ve got this little hollowing in the bone, this fossa known as the supraspinous fossa. Because it’s above the spinous [00:04:23], so ‘supraspinous’ fossa. And you’ve got the infraspinous fossa.

 

On the anterior surface, you’ve got a fossa, which is called the subscapular fossa. It’s underneath the scapula, so subscapular fossa.   Three fossa or fossae.

 

I’ve mentioned before this other fossa here which articulates with the humerus. This is called the glenoid fossa and this is the point of articulation with the humerus, which is the bone of the upper arm. I’ll just isolate the scapula again and you can have a look at that. You can see this shallow hollowing, the glenoid fossa and you’ve got two tubercles above and below it.

 

Above the glenoid fossa, you’ve got the supraglenoid tubercle and below it, you’ve got the infraglenoid tubercle.   These tubercles are a point of attachment for muscles.   The infraglenoid tubercle is the point of origin for the long head of the triceps muscle. The supraglenoid tubercle is the point where the long head of the bicep muscles attaches.

 

I’ll just switch over to this model and you can actually see that. This is the big triceps muscle and you’ve got this long head of the triceps attaching to the infraglenoid tubercle. If I just rotate the model around, you can see this, the biceps muscle anteriorly on the upper arm and it’s got this one head, this tendon running up between the two tuberosities of the humerus and inserting onto the greater, so the supraglenoid tubercle.

 

Just going back to the scapula again, one last thing to point out is this little notch here.   You’ve got a notch at the top of the scapula just medial to the coracoid process, which is called the suprascapular notch because it’s at the top of the scapula, this little notch here.

 

That’s the shoulder girdle or pectoral girdle, whichever one you prefer. You’ve got the clavicle and the scapula and you’ve got the various different aspects, the different features of the scapula that are important to be aware of, different processes and surfaces, angles, borders and that kind of thing.