Clavicle (Clavicula)
Anatomically, the clavicle (clavicula) is an S-shaped long bone. Its central portion is termed the shaft or body of the clavicle (corpus claviculae). On the inferior surface of the shaft runs the subclavian groove (sulcus musculi subclavii).
The clavicle clearly presents two ends:
- Medial or sternal end (extremitas sternalis). It is flattened and features the sternal articular surface (facies articularis sternalis) for articulation with the clavicular notch of the manubrium of the sternum. This end also features the impression for the costoclavicular ligament (impressio ligamenti costoclavicularis).
- Lateral or acromial end (extremitas acromialis). This end is flat and bears the acromial articular surface (facies articularis acromialis) for articulation with the acromion of the scapula. Located here is the tuberosity for the coracoclavicular ligament (tuberositas ligamenti coracoclavicularis), which consists of two important landmarks: the conoid tubercle (tuberculum conoideum) for attachment of the conoid ligament, and the trapezoid line (linea trapezoidea) for attachment of the trapezoid ligament.
The surfaces of the bone differ significantly: the superior surface (facies superior) is completely smooth, whereas the inferior surface (facies inferior) is rough due to ligamentous attachments. The main function of the clavicle is to connect the upper limb to the axial skeleton and provide a bony strut for muscles.
Scapula: Borders, Angles, and Surfaces
The scapula (scapula) is a flat, triangular bone located in the frontal plane of the human body.
For precise anatomical description, the scapula features three borders:
- Medial border (margo medialis).
- Lateral border (margo lateralis).
- Superior border (margo superior).
Corresponding to these borders, the bone possesses three angles: the superior angle (angulus superior), inferior angle (angulus inferior), and lateral angle (angulus lateralis).
The surfaces of the scapula bear important anatomical features. The anterior surface, also known as the costal surface (facies costalis seu anterior), contains a broad subscapular fossa (fossa subscapularis). The posterior surface (facies posterior) is more complex, divided by a prominent bony ridge, the spine of the scapula (spina scapulae). This spine divides the posterior surface into two isolated areas: the supraspinous fossa (fossa supraspinata), located above, and the infraspinous fossa (fossa infraspinata), located below the spine.
Processes and Articular Features of the Scapula
The scapula features several processes and articular elements that are critical for the mobility of the entire shoulder girdle.
- Acromion (acromion) — a large projection bearing the articular facet for articulation with the clavicle (facies articularis clavicularis).
- Coracoid process (processus coracoideus) — projects anteriorly and lies just superior to the glenoid cavity.
Between the coracoid process and the acromion lies the scapular notch (incisura scapulae). As an anatomical variant, this notch can sometimes be bridged by bone, forming the scapular foramen (foramen scapulae).
The primary articular feature is the glenoid cavity (cavitas glenoidalis), which serves as the socket for the glenohumeral (shoulder) joint. The periphery of the cavity is slightly constricted, forming the neck of the scapula (collum scapulae). Superior to the glenoid cavity is the supraglenoid tubercle (tuberculum supraglenoidale), and directly inferior to it is the infraglenoid tubercle (tuberculum infraglenoidale).