In this anatomy lesson, I’m going to cover the clavicle and scapula bones. These bones are part of the appendicular skeleton, and together they form the pectoral girdle (also called shoulder girdle), which attaches the upper limb to the axial skeleton.
Clavicle Bone Anatomy (Collarbone)
The clavicle bone, also called collarbone, is a small, curved bone that sits horizontally on each side of the superior thorax. It attaches to the scapula laterally at the acromioclavicular joint, and the sternum (breastbone) medially at the sternoclavicular joint.
Anatomists classify the clavicle as a long bone, and it gets its name from a Latin word that means “small key.”
The clavicle bone serves as an important landmark when performing healthcare assessments. For example, the “midclavicular line” is an imaginary line that runs down the body from the middle of the clavicle, and it’s used to determine the location of the apical pulse, as well as the two vertical lines that make up the nine abdominal regions. The clavicle bone is also a common fracture point for athletes.
- Acromial End – Looking at the right clavicle, you’ll notice the acromial end at the lateral side (at the side of the body near the arm), which is flattened. The facet at the acromial end is going to articulate with the acromion of the scapula, forming the acromioclavicular joint, a plane joint that allows gliding movements.
- Trapezoid Line – This ridge allows for the attachment of the trapezoid ligament.
- Conoid Tubercule – The word “conoid” comes from a Greek word that means “cone shape,” and this allows for the attachment of the conoid ligament.
- Impression for Costoclavicular Ligament – Toward the medial end of the clavicle, we have an impression called the impression for the costoclavicular ligament. The prefix “costo” refers to the ribs. Just as the name suggests, this impression allows for the attachment of the costocalvicular ligament, which attaches the clavicle to the cartilage of the first rib.
- Sternal End – On the medial side of the clavicle, we have the sternal end. Remember, medial means toward the midline of the body, and the sternum is the breastbone. This part of the clavicle is going to articulate with the manubrium of the sternum.
Scapula Bone Anatomy
The scapula, also called shoulder blade, is a triangle-shaped bone on the posterior side of the body that forms the posterior part of the pectoral girdle. Three is the magic number for the scapula: It has three depressions (called fossae), three borders, and three angles.
Anatomists classify this bone as a flat bone, despite having some rather irregular structures. While this bone does articulate with the humerus and clavicle, it does not articulate with the ribs.
- Coracoid Process – On the anterior side of the scapula, a small hook-like structure extends and bends out laterally like a hook. In fact, the word “coracoid” comes from a Greek word that means “raven-like” hooked beak. This allows for the attachment of muscles such as the short head of the biceps brachii, pectoralis minor, and the coracobrachialis, as well as several ligaments.
- Glenoid Cavity – On the lateral side of the scapula, there is a rounded depression at the superior (top) portion called the glenoid cavity. This cavity forms a ball-and-socket joint with the head of the humerus bone, called the glenohumeral joint. Above and below the glenoid cavity, there are two tubercles (bumps):
- Supraglenoid Tubercle – The one above the glenoid cavity is the supraglenoid fossa. Supra means “above.” This allows for the attachment of the long head of the biceps brachii.
- Infraglenoid Tubercle – The infraglenoid tubercle is below the glenoid cavity (infra=below), and it allows for the attachment of the long head of the triceps brachii.
- Subscapular Fossa – The anterior (or front) side of the scapula contains a minor depression (fossa), which allows the subscapularis muscle to attach.
Three Angles on the Scapula:
- The Lateral Angle – The glenoid cavity is located at the scapula’s lateral angle, also called the head of the scapula, which is a thicker part of the bone.
- Inferior Angle – At the inferior (bottom) part of the scapula, we see the inferior angle. Again, superior means toward the top or head of a structure, and inferior means away from the head of a structure or toward the bottom. This angle allows for the attachment of the teres major muscle at the dorsal (back or posterior) side.
- Superior Angle – At the superior end of the scapula, a small triangular projection is formed at the junction of the superior border and medial border, called the superior angle, which allows fibers from the levator scapulae to attach.
Three Borders on the Scapula
It will be easy to locate these three borders if you remember your directional terms:
- Superior border – The superior border starts with an “s,” which is helpful in remembering the two main characteristics of this border: It’s the sharpest and shortest. It is located at the top of the scapula and allows for the attachment of the omohyoid muscle.
- The Suprascapular Notch is located on the superior border. The prefix “supra” means “above or over.” The suprascapular nerve runs through this notch. As I said before, all of these little notches and bumps on these bones are there for a reason.
- Medial Border – The medial border is the longest border of the scapula, located toward the midline of the body. It includes the portion of the scapula between the inferior and superior angles, and allows for the attachment of muscles such as the serratus anterior, levator scapulae, and the rhomboid major and minor.
- Lateral Border – The lateral border is always going to be on the same side of the scapula as the glenoid cavity, and this is the thickest of the three borders. Found between the inferior angle and the lower margin of the glenoid cavity, this border allows for the attachment of muscles such as the subscapularis, teres minor and teres major.
Posterior Scapula Anatomy
- Spine – The spine is always on the back (or posterior side) of the scapula, which is easy to remember because the spine is another word for backbone. This bony projection allows for the attachment of the trapezius and deltoid muscles.
- Acromion – The acromion of the scapula, which means “highest shoulder” in the Greek, is the lateral part of the spine. This bony process articulates (forms a joint) with the acromial end of the clavicle, forming the acromioclavicular joint, a plane joint that allows gliding movements.
- Supraspinous Fossa – The supraspinous fossa is a depression above the spine of the scapula. That’s what the name literally means. Supra means “above or over,” spinous refers to the spine, and fossa means depression. This allows for the attachment of the supraspinatus muscle.
- Infraspinous Fossa – The infraspinous fossa is a depression below the spine of the scapula. The prefix “infra” means below. The infraspinatus muscle originates in the infraspinous fossa.
Free Quiz and More Anatomy Videos
Ready to test your knowledge? Take our free (and quick!) clavicle and scapula anatomy quiz. Also, you might want to watch more of our anatomy and physiology lectures on YouTube, or check our anatomy and physiology notes.