How many fossas does a shoulder blade have

Scapula

Synonym: shoulder blade
English: scapula, shoulder blade, omoplate

1 definition

The Scapula forms the back part of the bony shoulder girdle. It is a predominantly flat, triangular bone that primarily serves as the muscle origin and forms an articulated connection with the humerus and clavicle.

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2 surfaces

2.1 Dorsal facies

Image description: 1 - Fossa supraspinata; 2 - scapular spine; 3 - infraspinate fossa; 4 - margin superior; 5 - superior angle; 6 - Margo medialis; 7 - Angulus inferior; 8 - lateral margin; 9 - lateral angle; 10 - acromion; 11 - coracoid process; 12 - origin of the teres major muscle; 13 - Origin of the teres minor muscle

2.2 Facies ventralis (costalis)

  • The ventral surface of the scapula facing the ribs shows an extensive concave pit, the subscapular fossa.
  • The medial 2/3 of the fossa are defined by sloping edges that serve as tendon attachments to the subscapularis muscle.
  • The subscapular fossa is separated from the medial margin by smooth triangular areas at the inferior and superior angulus - sometimes also called the angulus medialis. This is where the serratus anterior muscle comes in.

Image description: 1 - subscapular fossa; 2 - Angulus lateralis with Cavitas glenoidalis; 3 - coracoid process; 4 - acromion; 5 - margin superior; 6 - Scapular notch; 7 - superior angle; 8 - Margo medialis; 9 - Angulus inferior; 10 - lateral margin; 11 - Infraglenoid tubercle

3 edges

3.1 Margo superior

The superior margin is the shortest edge of the scapula. It runs from the superior angle to the base of the coracoid process. There you can see a clear incision, the Incisura scapulae, which is spanned by a ligament, the Ligamentum transversum scapulae superius. The suprascapular nerve runs through the incision. The adjacent part of the superior margin serves as the insertion of the omohyoideus muscle.

3.2 lateral margin (axillary)

The lateral margin is the most massive of all three edges of the scapula. It begins at the lower edge of the glenoid cavity and ends at the inferior angle. Directly below the glenoid cavity is a small, rough elevation, the infraglenoid tubercle. This is where the long head (caput longum) of the triceps brachii muscle has its origin.

3.3 Margo medialis (vertebralis)

The medial margin is the longest edge of the scapula. It runs from the superior angle to the inferior angle. Numerous muscles attach to the medial margin, including the musculus rhomboideus major, the musculus rhomboideus minor, the pars inferior of the musculus serratus anterior and the musculus levator scapulae.

4 angles

4.1 Angulus superior

The superior angle arises from the meeting of the medial margin and superior margin. It is thin, smooth and rounded and serves as an attachment to some fiber strands of the levator scapulae muscle.

4.2 Inferior angle

The angulus inferior scapulae arises from the meeting of the margo medialis and margo lateralis. It's thick and rough. Its dorsal surface serves as a base for the teres major muscle and some fiber strands of the latissimus dorsi muscle.

4.3 Angulus lateralis

The angulus lateralis scapulae is the most massive part of the scapula and is also known as the "shoulder head". Here lies a flat, cartilage-covered joint socket, the glenoid cavity, which articulates with the head of the humerus.

5 prominent structures

5.1 Spina scapulae

The Spina scapulae ("Shoulder bone") is a compact bone ridge running across the dorsal surface of the scapula, which divides the scapula topographically into the supraspinous and infraspinous fossa. It begins relatively flat at the medial margin with a smooth triangular surface, the trigonum spinae scapulae, over which the tendon attachment of the caudal part of the trapezius muscle slides. On its way laterally, the spine rises and ends in the acromion, which covers the shoulder joint. The base of the spine is laterally separated from the acetabulum by the spinoglenoid incisura. The trapezius muscle attaches to the superior part of the spine. The spina scapulae is the origin of the deltoid muscle.

5.2 Coracoid process

The Coracoid process ("Raven beak") is a strong, hook-shaped bony process of the scapula. It arises cranially from the glenoid cavity and first moves cranially and medially, and then swings ventrally and laterally. On its way it tapers. The common tendon of origin of the caput breve of the musculus biceps brachii and the musculus coracobrachialis attaches to the processus coracoid. Furthermore, the insertion of the pectoralis minor muscle and various ligaments, e.g. the coracoacromiale ligament and the coracoclavicular ligament, insert here.

5.3 Acromion

The Acromion ("Shoulder height") emerges from the spina scapulae and forms the highest point of the shoulder blade. Its superior face is roughened and, like the lateral edge of the acromion, serves as the origin for the deltoid muscle. Here the bone lies directly subcutaneously and can be palpated as an anatomical reference point. At the medial edge of the acromion there is a small oval surface that creates the joint connection to the clavicle. This joint is called the acromioclavicular joint.

5.4 Glenoid cavity

The Glenoid Cavitas is a cartilage-covered, oval joint socket, the vertical diameter of which is larger than the horizontal. Together with the humeral head, it forms the shoulder joint (articulatio humeroscapularis). It is surrounded by a lip, the glenoid labrum, which deepens the joint socket. The supraglenoid tubercle lies above the joint socket. This is where the long head of the biceps brachii muscle has its origin. Below the socket is the infraglenoid tubercle, where part of the tendon of the long head of the triceps brachii muscle originates.

6 development

The scapula develops from several bone nuclei. During the third month of the fetal life, a large bone nucleus develops in the area of ​​the supraspinata and infraspinata fossae and the scapular spine. In the first year of life a nucleus forms in the coracoid process, whereas several smaller nuclei can appear distributed over the entire scapula between the 11th and 18th year of life. In the course of growing up, all nuclei fuse between the ages of 16 and 22. In rare cases, the nucleus that appears between the ages of 15 and 18 can remain independent in the acromion (os acromiale).

7 function

The mobility of the scapula extends the range of action of the shoulder girdle and thus of the arm. Your movement options include:

The structure of the scapula is a frame construction: the bones parallel to the edge unite in the neck piece (collum scapulae), which carries the socket for the humeral head. As a result, the joint pressure is transferred to the frame and is mainly absorbed by the lateral margin.

8 clinic

When certain back or shoulder muscles are paralyzed, the scapula protrudes, which is called the scapula alata.

see also:Scapular fracture