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.
- 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.
- 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.
- 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.
- 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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