Dog · Set · Thoracic limb

The metacarpal bones

Ossa metacarpalia

Five bones between the carpus and the digits. Four of them carry the paw; the first is short and belongs to the dewclaw.

How they differ along the set

What changes from one end of the series to the other, which is most of what there is to know about any one of them.

Metacarpals II to V are the main bones: irregular rods of fairly even thickness.Miller 2020, p. 328
II and V are shorter than III and IV, and four-sided — particularly at the base, where III and IV are more triangular.Miller 2020, p. 328
They diverge towards the toes, leaving the intermetacarpal spaces between them.Miller 2020, p. 328
The base of the second reaches further up than that of any of the others.Miller 2020, p. 328
The sharp sagittal crest on the palmar part of each head is what keeps the pair of sesamoid bones there from slipping sideways.Miller 2020, p. 328
The walls are at their thickest through the middle of the shaft and thin towards both ends, so the joint cartilage sits on a thin shell of bone.Miller 2020, p. 329
Each of the four main bones has a nutrient foramen on the upper third of its palmar surface.Miller 2020, p. 329
The main bones ossify from a distal growth plate; the first metacarpal's is at the proximal end instead.Miller 2020, p. 329

What a member of this set carries, and what each part is called in the Nomina Anatomica Veterinaria.

Sesamoid fossaeFossae sesamoidales: The hollows that separate the heads from the bodies on the dorsal side.Miller 2020, p. 328
Sesamoid impressionsImpressiones sesamoidales: The matching marks on the palmar side.Miller 2020, p. 328
Sagittal crestsCristae sagittales: The sharp ridges on the palmar part of each head, between the paired sesamoids.Miller 2020, p. 328

In order along the set. Any one of them can be singled out in the model above, with the picker beneath it.

First metacarpal boneOs metacarpale IMedial, short; carries the dewclaw (digit I)
Metacarpal 2Os metacarpale II
Metacarpal 3Os metacarpale III
Metacarpal 4Os metacarpale IV
Metacarpal 5Os metacarpale V

Where to read this set in full, and where everything above was read.