The clavicle and humerus are joined together by the triangular scapula, also referred to as the shoulder blade. This bone is situated posteriorly (back side of the body). The scapula is essential for maintaining the stability of other bones involved in shoulder movement.
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What is Scapula?
The scapula, commonly referred to as the shoulder blade, is a flat, triangular bone that sits over the rear ends of ribs two to seven. The scapula, clavicle, and manubrium of the sternum together form the pectoral girdle (shoulder), which joins the axial skeleton to the upper limb of the appendicular skeleton.
The scapula is a significant bone as it serves as an attachment point for a number of the shoulder and arm muscles.
Anatomy – Parts of the Scapula
The anatomy of scapula parts includes borders and angles, surfaces and articulations.
Borders and Angles
A flat blade with a triangular form and a pointed bottom constitutes the scapula’s body. Due to its triangle shape, it has three borders, and they are:
- Superior Border: It is the thinnest and shortest border.
- Medial Border: It is also known as the vertebral border and is a thin border that runs perpendicular to the vertebral column.
- Lateral Border: It extends from the base of the axilla towards its apex and is also referred to as the axillary boundary. It is the strongest and thickest of the three borders.
The scapula has three angles as well. The superior border and lateral border join to form the lateral angle. The superior angle is formed when the superior border and medial border converge. The medial border and lateral border converge to produce the third angle, known as the inferior angle.
Surfaces
The scapula features two surfaces; the costal surface is smooth on the anterior side. The inferior infraspinous fossa is significantly more extensive and convex than the superior supraspinous fossa and is located on the posterior surface of the scapula.
Costal Surface
It is the part of the scapula that is anterior to the ribcage or thoracic cage.
Lateral Surface
This part of the scapula surface faces the humerus. The primary features of the lateral surface are:
- Glenoid Fossa: It is a narrow pyriform chamber found at the lateral scapular angle.
- Supraglenoid Tubercle: It is a tiny coarse projection found close to the coracoid base process directly above the glenoid fossa.
- Infraglenoid Tubercle: It is a rough imprint found beneath the glenoid fossa on the lateral side of the scapula.
Posterior Surface
This surface points outwards. This is the origin of most of the shoulder’s rotator cuff muscles. The significant anatomical features of the posterior surface are:
- Spine: A triangular bone plate divides the scapula’s dorsal side into infraspinous and supraspinous fossae.
- Supraspinous Fossa: It is located above the scapular spine. It is smooth, concave, and wider at the vertebral end than at the humeral end.
- Infraspinous Fossa: It is the region of the scapula that lies beneath the spine. It is convex and is significantly larger than the prior one.
- Acromion: It is a significant bony outgrowth on the top of the scapula. It curves across the shoulder joint, connecting with the clavicle at the acromioclavicular (AC) joint.
Also, read: Acromion Process
Articulations
- Glenohumeral Joint: The rounded head of the humerus and the glenoid fossa of the scapula join to form this ball and socket joint.
- Acromioclavicular Joint: It is a gliding joint formed between the acromion and the clavicle structures.
Related Links:
- Where is Scapula Bone located?
- Short Notes Disorders of Bones
- What are the Functions of the Human Skeletal System?
Main Page: BYJU’S NEET
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