Most Things Biology

Pectoral Girdle: Scapula

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5–7 minutes

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The scapula or shoulder blade is a triangular shaped bone with a complex attachment point to the clavicle.

Three views of a right scapula (shoulder blade): posterior, lateral, and anterior. The posterior view shows the flat, triangular bone from the back. The lateral view shows the side of the bone with the glenoid fossa, where the humerus (upper arm bone) articulates. The anterior view shows the concave surface of the bone from the front
3 views of right scapula: posterior, lateral, anterior.
Scapula Study Sheet
  • Acromion process
  • Coracoid process
  • Superior angle
  • Inferior angle
  • Superior border
  • Medial border
  • Lateral border
  • Spine
  • Supraspinous fossa
  • Infraspinous fossa
  • Subscapular fossa 
  • Glenoid fossa

The pectoral girdle is the attachment point for your arms.  Any girdle is an attachment point for limbs.  Humans and other mammals have two girdles: the pectoral and the pelvic.  The pectoral girdle consists of what you might call the shoulder and the collarbone.  These are the scapula and the clavicle.  The humerus fits into the scapula, or shoulder blade in what you might call a ball and socket joint.  The clavicle, or the collarbone stabilizes the shoulder blade with an attachment to your sternum or breastbone.  Touch your collarbone, follow it over to the mid line of your neck to feel the attachment to the sternum.  You can also feel the jugular notch right at the center of the sternum. 

The socket into which the humerus fits is called the glenoid cavity or the glenoid fossa.   The scapula sits on the back of your rib cage.  It’s amusing because many people get a disarticulated scapula. They often mistakenly think that this big long border here by the vertebra is along the lateral side.  It’s not.  That misconception may not happen in a totally virtual class, but when students study the scapula, they always do that.   When you approach a scapula, you have to orient it lateral and medial.  You know that this glenoid cavity is the socket and should face laterally. 

Let’s start by looking at the scapula from a posterior view. One important structure on the posterior side is the spine of the scapula. This structure will be used as a landmark to define other structures. A long border which faces the vertebra is called the medial or vertebral border. I don’t know why but this is the one that students always think for some reason is lateral. I think you want it to be wings. It is not. The glenoid cavity must face laterally. This allows the humerus to connect or articulate with it for the shoulder.  The glenoid fossa kind of slants down into the lateral border. The glenoid fossa has to be lateral and so this is the lateral border.

Let’s stick with the posterior view and define 3 structures.  We are going to use the spine as a landmark for locating these structures.  The spine itself kinda curves into this spoon like structure laterally over toward the laterally facing glenoid fossa.  This is the acromial process or the acromion.  The spine curves into the acromion.  Superior to the spine is the supraspinous fossa.  Listen to the name: supra meaning above and spinous referring to the spine.  The fossa below the spine becomes easy to name.  It is the infra spinous fossa.  Let’s take a moment to look at the three structures on the posterior side of the scapula. They are all easily located with the spine. 

Let’s now do the front of the scapula or the anterior side.  It’s always a good idea when you look at pictures. Try to locate at least one thing that you already know in the picture.  I’ve been using the glenoid fossa also called the glenoid cavity as the landmark here.  I like using it because it always tells me which is the lateral facing side of the bone. 

This is the anterior side of the scapula. The side with the glenoid cavity is the lateral side. Therefore, this is a right scapula. We are seeing these sides as such. Confirm this by imagining your patient in front of you.  This big area here is the subscapular fossa.  Listen to the name: sub meaning under and scapular referring to the entire bone.  The other fossa referred to the spine.  Think about where this anterior facing side of the scapula is.  This subscapular fossa seems to be facing the rib cage.  The other structure that we can see from the anterior side is the coracoid process.  Students often confuse this with the acromion or the acromial process.  Yeah sometimes you can see both from the posterior side of the bone and then you get confused.  But, you know that the acromion is an extension of the spine of the scapula. The coracoid process is not. OK, so this is the scapula: 4 fossa, 2 processes, 2 borders, and a spine.


We’ve studied the shoulder. We can now start to understand why it dislocates so easily. We also know in what direction dislocations commonly occur.  Look at the glenoid cavity.  It’s kind of shallow compared to the ball and socket that the hip forms with the femur.  It’s the processes of the spine, the clavicle, and all the ligaments that really stabilize the shoulder.  This is why you have so much mobility of the arm.  Take your arm and rotate it in a circle as wide as you can.  Now, do that with your hip.  You can’t.  So, the shoulder has all this mobility.  But, the mobility comes at a price in that the shoulder is much easier to dislocate than the hip.  In fact, the shoulder will frequently dislocate in the anterior and inferior direction.  The acromion prevents it from going to the posterior direction. The clavicle prevents it from going in the superior direction.  Once a shoulder is dislocated, the solution is to pull on the arm in an inferior and lateral direction.  This will release the bones and allow the humerus to situate itself on the glenoid cavity once again (at least, that is what the paramedic said right after he said, “We can do this here, now, or we can do it later in the hospital.”). 

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Anterior view of a human shoulder skeleton demonstrating the relationship between the clavicle, humerus, and acromial process. The sternal end of the clavicle articulates near the center while the acromial end articulates at the shoulder.
Anterior shoulder anatomy showing clavicle, humerus head, and acromial process.
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Illustration of anterior shoulder anatomy features the acromial process, glenoid cavity, and coracoid process. The bones are rendered in grey against a white background. The image shows the clavicle and part of the ribcage
Anterior shoulder anatomy showing acromial & coracoid processes, and glenoid cavity.
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A posterior view illustration of the human shoulder anatomy. The skeletal structure consists of the scapula, a series of ribs partially visible behind it, and the upper section of the humerus. Green lines with descriptive text point to key anatomical locations: the superior angle, medial (vertebral) border, inferior angle of the scapula, and the lateral (axial) border.
Posterior view of the shoulder showing the scapula, ribs, and humerus, with labels for anatomical borders and angles.
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Anatomical illustration detailing the posterior view of the shoulder. Key features are labeled, including the spine of the scapula, the infraspinous fossa, the supraspinous fossa, and the acromial process. The image shows the bone structure and their spatial relations.
Anatomical illustration of the posterior shoulder showing the spine, infraspinous fossa, supraspinous fossa, and acromial process.
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An anterior anatomical illustration of a shoulder. Key structures like the acromial process, acromial end of the clavicle, coracoid process, and subscapular fossa are labeled with arrows. The ribs and spine can be seen.
Anterior view of the shoulder, illustrating the acromial process, clavicle, coracoid process, and subscapular fossa.
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