Appendicular Skeleton - Thoracic Limb

• Scapula - the only remaining bone in the pectoral girdle of most domesticated animals
• SCAPULA comparative (shape):

  Distinctly triangular in ox and sheep; less so in dog and cat
• SCAPULA comparative (Scapular Cartilage):

  Well developed in horse; a broad thin structure in horse, ruminants, and pigs
• SCAPULA comparative (Spine):

  Divides the lateral surface of the scapula into almost equal suptaspinous and infraspinous fossae in dog and pig
• SCAPULA comparative (Spine):

  In the ox and horse, the spine is placed more cranially so that the supraspinous fossa is smaller than the infraspinous fossa
• SCAPULA comparative (Spine):

  In horse, the spine fades out distally
• SCAPULA comparative (Tuber spinae scapulae/Trapezius tubercle):

  Absent in the dog but well developed in pig and horse
• SCAPULA comparative (Tuber spinae scapulae/Trapezius tubercle):

  Poorly developed in cat and ox; prominent and pigs (overhanging the infraspinous fossa)
• SCAPULA comparative (Acromion):

  Absent in pigs and horses
• SCAPULA comparative (Suprahamate process):

  Caudal additional projection in the acromion found only in cat
• Humerus is the largest bone of the thoracic limb. It is a long bone that lies obliquely against the ventral part of the thorax, more horizontally in the large species than in small
• HUMERUS comparative (Size):

  Relatively shorter and more robust in horses and cattle than in small ruminants and carnivores
• HUMERUS comparative (Greater (lateral) tubercle):

  Divides into cranial and caudal parts in the horse and cattle. Larger than the lesser tubercle in dogs, more or less equal in horses 
• HUMERUS comparative (Lesser (medial) tubercle):

  Divides into cranial and caudal parts in the horse and cattle
• HUMERUS comparative (Intertubercular/Bicipital groove):

  Single in the dog and pig; divided by a low sagittal ridge in the ruminants, and a well developed ridge (intermediate tubercle) in the horse
• HUMERUS comparative (Intermediate tubercle):

  A prominence molded in the Intertubercular groove of horses
• HUMERUS comparative (Supratrochlear foramen):

  Present in dog, absent in pig, horse, ox, and horse
• HUMERUS comparative (Supracondylar foramen):

  The opening in the medial epicondyle present only in cat
• HUMERUS comparative (Lateral tuberosity):

  Massive and overhangs Bicipital groove in ox and sheep. In pig, it almost converts the Bicipital groove into a foramen
• HUMERUS comparative (Humeral condyle):

  In large animals, it engages with the radius and has the form of a trochlea
• HUMERUS comparative (Humeral condyle):

  In the dog and cat, it is divided into the medial area (trochlea) for the ulna and lateral area (capitulum) for the radius
• HUMERUS comparative (Humeral condyle):

  Has three fossae in the cat
• RADIUS and ULNA comparative (Fusion of the two bones):

  The ulna is completely fused (by ossification) in ruminants and horse, the distal part of the limb is fixed in the position of pronation; connected by a fibrous tissue in pig
• RADIUS and ULNA comparative (Fusion of the two bones):

  In horse, the fusion reaches its extreme, in which only the upper end of the ulna remains distinct. Distal two-thirds of the bone dissappears and it is just represented in the distal end of the radius by the lateral styloid process
• RADIUS and ULNA comparative (Fusion of the two bones):

  The two bones are separate in carnivores about 45 degrees of supination is allowed in dog, and somewhat more to the cat
• RADIUS and ULNA comparative (Antebrachial interosseous space):

  Long and narrow in the dog, pig, and chicken, reduced to two short spaces in ruminants; and just one space in horse
• RADIUS and ULNA comparative (Proximal extremity of the RADIUS):

  Tends to be more circular in carnivores, in which supinatory capacity remains; transversely widened in the others
• RADIUS and ULNA comparative (Neck of the RADIUS):

  Distinct only in carnivores
• RADIUS and ULNA comparative (Distal extremity of the radius):

  Concave in its cranial part and convex in its caudal part in ungulates
• RADIUS and ULNA comparative (Distal extremity of the radius):

  Slightly concave ovoid form in carnivores for some additional movements
• RADIUS and ULNA comparative (Size of ulna):

  Ulna is larger than the radius in pig and chicken; extremely slender in sheep
• RADIUS and ULNA comparative (Length):

  Radius is longer than ulna in horse; ulna is longer than the radius in others
• RADIUS and ULNA comparative (Olecranon):

  In dogs has a trituberculate summit
• In the dog, radial carpal bone is regarded by some workers as fused radial and intermediate carpal bone
• RADIAL carpal bone is individually present in all
• Intermediate carpal bone is absent in dog and cat
• Ulnar carpal is individually present in all
• Accessory carpal is individually present in all
• 1st carpal is absent in horse, ox, sheep, goat.
• 2nd carpal is fused with 3rd carpal in ox, sheep, and goat