Shoulder Girdle Anatomy Quiz

Shoulder Girdle

• Consists of clavicle (collar bone) & scapula (shoulder blade).
• Provides a mobile base for upper limbs to attach to the trunk.

Clavicle

• Bone shaped like an "S".
• Distances scapula and upper limb from chest wall.
• Articulates with sternum and acromion of scapula.
• Transmits forces to axial skeleton.
• Lacks marrow.
• Ossifies in membrane.

Scapula

• Triangular bone.
• Articulates with humerus at glenoid fossa.
• Prominent spine on posterior surface.
• Large, flat surfaces and roughened processes for muscle attachments.

Shoulder Girdle joints

• Sternoclavicular joint:
  • Saddle synovial joint.
  • Articular surfaces: sternal end of clavicle and clavicular notch of manubrium sterni and 1st costal cartilage.
  • Articular surfaces are covered by fibrocartilage
  • Synovial capsule encloses the joint.
  • Accessory ligaments: anterior and posterior sternoclavicular ligaments, costoclavicular ligament which is the major stabilizer of the joint, and a fibrocartilaginous disc dividing joint into two cavities.
• ** Acromioclavicular joint:**
  • Plane synovial joint.
  • Articular surfaces: acromial end of clavicle and clavicular facet of the acromion process of the scapula.
  • Accessory ligaments: acromioclavicular ligament and the strong coracoclavicular ligament, which has two parts-trapezoid and conoid, that provide stability.

Scapular Movements

• ** Elevation:** upward movement.
• ** Depression:** downward movement.
• ** Retraction:** backward movement,
• ** Protraction:** forward movement.
• ** Upward rotation:** rotating scapula upwards.
• ** Downward rotation:** rotating scapula downwards.

Muscles of the Pectoral region

• Location: Anterior chest wall.
• Consists of:
  • Pectoralis major.
  • Pectoralis minor.
  • Serratus anterior.
  • Subclavius.

Pectoralis Minor

• Attachments: Between upper ribs and coracoid process of scapula.
• Action: Protraction and depression of scapula.

Subclavius

• Attachments: Between first rib (costal cartilage) and clavicle.
• Nerve Supply: Nerve to subclavius.
• Action: Stabilizes the clavicle.

Serratus Anterior

• Attachments: From upper 8 or 9 ribs anteriorly to the medial border of scapula posteriorly.
• Nerve Supply: Long thoracic nerve.
• Action: Protraction and rotates the scapula to raise arm above 90 degrees.
• Long thoracic nerve can be injured in radical mastectomy operations.

Long thoracic nerve injury

• Results in paralysis of serratus anterior.
• Causes weakness in arm abduction above 90 degrees.
• Inability to push with arm.
• "Winging of the scapula": medial and inferior borders of scapula become prominent.
• Tested by patients pushing against the wall.

Muscles of the back involved in movements of the shoulder girdle

• Superficial Layer: Trapezius.
• Deep Layer: Levator scapulae, Rhomboideus minor, Rhomboideus major.

Trapezius muscle

• Attachments: From skull and upper half of vertebral column to scapula and clavicle.
• Nerve Supply: Spinal part of the accessory nerve (11th cranial nerve).
• Action: Works with serratus anterior to rotate the scapula to raise arm above 90 degrees.
  • Upper fibers: elevate scapula.
  • Middle fibers: retract scapula.
  • Lower fibers: depress scapula.

Paralysis of Trapezius muscle

• Weakness in raising arm above 90 degrees.
• Weakness in retracting scapula.
• Flattening of lower neck.
• Sagging of shoulder.

Deeper Layer of muscles of the back

• Levator scapulae, Rhomboideus minor, Rhomboideus major
• Attachments: Extend between the vertebral column and medial border of the scapula.
• Nerve Supply: Dorsal scapular nerve.
• Action:
  • Levator scapulae: elevates the scapula.
  • Rhomboideus minor & major: retract the scapula.

Movements of the Scapula

• ** Elevation:** by upper fibers of trapezius and levator scapulae.
• Depression: by lower fibers of trapezius and pectoralis minor.
• ** Protraction:** by serratus anterior and pectoralis minor.
• Retraction: by middle fibers of trapezius, and rhomboideus minor and major.
• ** Lateral (upward) rotation:** by upper and lower fibers of trapezius and lower 5 digitations of serratus anterior.
• ** Medial (downward) rotation:** by levator scapulae and rhomboids (minor and major).

Clavicle Injury

• Most common: fall directly on the shoulder with arm at the side.
• Usually occurs in middle one-third of the clavicle.
• Proximal piece is lifted superiorly by the sternocleidomastoid muscle.
• Distal fragment is pulled inferiorly by the arm.
• Treatment: usually non-operative.

Acromioclavicular Joint Injury

• Despite strong ligaments, joint can separate following a fall on shoulder or outstretched arm.
• Acromion is pushed under the clavicle, tearing the coracoclavicular ligament.

Axilla

• Arm pit.
• Has an apex, base, and 4 walls (anterior, posterior, medial & lateral).

Test your knowledge on the anatomy of the shoulder girdle, including the clavicle and scapula. This quiz covers the structure, function, and joints associated with the shoulder girdle. Delve into details about the bones and their articulations.