Veterinary Gross Anatomy

SCAPULA
(Ox, Sheep and Goat, Horse, Dog, Pig, Rabbit, Fowl)

Ox

• It is flat, triangular bone, situated on the antero-lateral aspect of the thorax and directed obliquely downward and forward. The clavicle is absent. It is connected to the axial skeleton only by muscles.
• It has two surfaces, three borders and three angles .
• The lateral surface or the dorsum is wide above and narrow below.It is traversed by the scapular spine, which divides the lateral surface into an cranial supraspinous fossa and the caudal infraspinous fossa, the former being the smaller. The free edge of the spine is in great part subcutaneous, somewhat rough and tuberous in the middle for the attachment of trapezius and is prolonged downward to form the acromion process for the deltoideus muscle. The supraspinous fossa lodges the supraspinatus muscle. The infraspinous fossa is occupied by the infraspinatus and the muscular ridges at its lower part are for the origin of teres minor. The costal or ventral surface presents a shallow depression called subscapular fossa , which lodges the subscapularis. The upper third of this surface presents cranially a triangular rough area for the serratus cervicis and posteriorly a rough line for the serratus thoracis.
• The cranial border is thin, convex above and concave below. The caudal border is thick, presents the nutrient foramen in the lower third and is rough for deltoideus, teres major and long head of triceps muscles. The vertebral border is thick, pitted and carries in life the scapular cartilage, the unossified part of the fetal scapula. The medial face of the cartilage gives attachment to the rhomboideus.
• The cranial or cervical angle is thin. The caudal  or dorsal angle is thick. The ventral or glenoid angle carries the glenoid cavity and cranial to it the tuber scapulae.The former meets the head of the humerus to form the shoulder joint. The rim of the cavity presents the glenoid notch on the craniolateral aspect. The tuber scapula is for the biceps brachii and presents the coracoid process on its medial aspect for the coraco brachialis.

 

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Sheep and Goat

• The vertebral border is longer and the neck is narrower.
• The scapular spine is less tuberous.
• The inferior or glenoid extremity is relatively longer, since the tuber scapula is connected with the rim of the glenoid cavity.
• Rim of the subscapular fossa is extensive.

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Horse

• The acromion process is absent.
• The subscapular fossa is deeper and partly separates two triangular rough areas in the upper third.
• The glenoid notch is on the antero-medial aspect of the rim.
• On its postero-lateral aspect the rim presents a tubercle for teres minor.
• The tuber scapula is larger and placed further away from the glenoid cavity.

 

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Pig

• Scapula of the pig is very wide.
• The scapular spine is triangular and is very wide in its middle, which curves backward over the infraspinous fossa and bears large tuberosity called tuber spine.
• Acromion process is rudimentary.
• The cranial border is slightly convex, thick and rough in its middle.
• The caudal border is wide and slightly concave.
• The vertebral border is convex and the scapular cartilage is not so extensive as in horse and ox.
• The cranial angle is thin and bent medially. The caudal angle is thick and is at right angle.
• The glenoid notch is absent.
• The tuber scapula is above the antero-medial part of the glenoid cavity.
• No distinct coracoid process and it unite with the rest of the bone at about one year.

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Dog

• The Clavicle, when present, is a small cartilaginous or bony plate embedded in the brachiocephalicus muscle, in front of the shoulder joint and does not articulate with the rest of the skeleton.
• In the Scapula, the spine is placed in the middle of the dorsum and increases in height from above downward, to the level of the glenoid cavity where it terminates in the acromion process.
• The vertebral border is convex and the scapular cartilage is in the form of a thin band.
• The glenoid cavity extends to the inferior face of the tuber scapula.
• The coracoid process is absent.

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Rabbit

• The coracoid process appears as slight enlargement at the cranial part of the rim of the glenoid cavity.
• The scapular spine possesses distally an elongated caudal process, the metacromion process along with the acromion process.

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Fowl

It has a clavicle, coracoid, and the scapula.

• The clavicle is a thin, bent rod directed downward and backward. The flat dorsal end rests against the scapula and the coracoid to form the foramen triosseum . The clavicles of two sides unite ventrally to form a flattened plate called Hypocleidium, which is attached to the rostrum of the sternum by a ligament. The two combined clavicles form the furcula and are also called “wish bone”.
•  The coracoid is rod like, directed backward, downward and inward. The upper extremity is prolonged into a hook-like process medially. It presents a small articular surface -the glenoid cavity for articulation with humerus. Below this, there is another area for articulation with scapula. The lower extremity articulates with the sternum.
• The scapula is a narrow saber-shaped bone placed parallel to the vertebral column. The anterior end presents a depression laterally which forms part of the glenoid cavity for the reception of the head of the humerus and a projection cranially -the acromion process, which meets the clavicle and coracoid to form the foramen triosseum. the posterior end lies at the level of the sixth rib.

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