What about Scapula Bone? Write down its features and Muscle attachments?

 SCAPULA

The Scapula is a thin bone placed on the posterolateral aspect of the thoracic cage.It has two surfaces, three borders , three angles and three processes. 

Features of Scapula:

Surfaces:

  • The Costal Surface is concave and is directed medially and forwards.It is marked by three longitudinal ridges.The part of the bone is rod-like.It acts as a lever for the action of seratus anterior.
  • The Dorsal Surface gives attachment to the spine of scapula which divides the surface into Supraspinous and Infraspinous fossa.
Borders:

  • The Superior border is thin and shorter.It presents the suprascapular notch.
  • The Lateral border is thick. It presents the infraglenoid tubercle.
  • The Medial border is thin.It extends from the superior angle to the inferior angle.
Angles:

  • The Superior angle is covered by the trapezius.
  • The Inferior angle is covered by latissimus dorsi.
  • The Lateral or glenoid angle is broad and bears the glenoid cavity or fossa.
Processes:

  • The spinous process is a triangular plate of bone with three borders and two surfaces.Its posterior border is called crest of the spine.
  • The Acromion process has two borders,medial and lateral; two surfaces superior and inferior.
  • The Coracoid process is directed forwards and slightly laterally. 

Muscle Attachments:
  • The Supraspinatus arises from the medial two-thirds of supraspinous fossa.
  • The Infraspinatus arises from the medial-two thirds of the infraspinous fossa.
  • The Deltoid arises from the lower border of the crest of spine and from the lateral border of acromion.
  • The Trapezius is inserted into the upper border of the crest of the spine.
  • The Serratus anterior is inserted along the medial border of the costal surface.
  • The long head of triceps brachi arises from the infraglenoid tubercle.
  • The Rhomboid minor is inserted into the medial border opposite the root of spine.
  • The Rhomboid major is inserted into the medial border between the root of spine and inferior angle.
  • The Teres major arises from lower one-third of the rough strip on dorsal aspect of lateral border.
  • The Teres minor arises by 2 slips from the upper two-thirds of the rough strip on the dorsal surface.
Clinical Anatomy:
  • Paralysis of serratus anterior causes Winging of scapula.The medial border of the bone becomes prominent and arm cannot be abducted beyond 90 degrees.

References:
BD Chaurasia's Anatomy of Upper Limb.
Chief Editor:
Krishna Garg, Pragati Sheel Mittal, Mrudula Chandrupatla.

About Author:
Tayyba Saleem ( PT )
Doctor of Physical Therapy.

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