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→Metacarpal Bones
===[[Forelimb - Anatomy & Physiology#Metacarpal bones|Metacarpal Bones]]===
===[[Forelimb - Anatomy & Physiology#Metacarpal bones|Metacarpal Bones]]===
Dogs are '''digitigrade''' animals; this means that the weightbearing surface of their limbs is their digit. The canine phalanges are thus very important. They are virtually identical in their structure in the hindlimb and forelimb. The main differences are in the forelimb we have metacarpals and the metacarpophalangeal joint, the hindlimb equivalents are the metatarsals and the metatarsophalangeal joint. Also in anatomical planes we use the term ''palmar'' for forelimb and ''plantar'' for hindlimb. These terms are all interchangeable depending on whether you want to talk about the fore or hindlimb.
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The metacarpals are numbered medially to laterally 1 to 5 in direct correspondence with the numbers of the distal carpals. The shape of canine metacarpals are defined by their relative articulations. For example, the third and fourth carpal bones have a more square cross-section as these middle metacarpals bear the majority of the weight borne by that limb. Metacarpals 2 and 5 bear relatively less weight than 3 and 4 and have a more tringular cross-section.
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Each metacarpal has a proximal region referred to as the ''base'', a shaft or body and a distal extremity or ''caput''. The surface of the base of the metacarpal is relatively flat to provide articulation with the carpal bones. Each base also has medial and lateral bony prominences or facets where each metacarpal makes contact with the adjacent metacarpal. The caput of each bone articulates with the phalanges via a hemicylinderical surface that contains a central bony prominence or ridge. This articulation also has a pair of sesamoid bones on the palmer surface and even smaller single sesamoid bone on the dorsal surface of the joint.
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====Phalanges====
The proximal phalanx of the main digits (II - V) have a concave articular surface and the palmar border has a groove to accomodate the articular surface of the metacarpus when the joint is fixed. The distal head has two convex areas separated by a groove. The middle phalanx is roughly two-thirds the length of the proximal phalanx and its base has a sagittal ridge on the articular surface which articulates with the groove of the proximal phalanx. The head resembles that of the proximal phalanx. The distal phalanx is made up of a cone-shaped ungual process with a distinct collar called the 'ungual crest'. The deep ungual groove distal to the crest provides attachment for the proximal border of the claw and articulates with the middle phalanx via a small sagittal crest. A bony sesamoid bone is found on the dorsal aspect of the metacarpophalangeal joint. The 'dew claw' (metacarpal I) is normally present in the forelimb but often not in the hindlimb. It normally only consists of two phalanges that resemble the proximal and distal ones.
These are covered in detail in the [[Canine Phalanges - Anatomy & Physiology|canine phalanges]] section.
These are covered in detail in the [[Canine Phalanges - Anatomy & Physiology|canine phalanges]] section.