Veterinary Dog Anatomy

Note: All the notes provided us from gcvs 

recomended book Guide To The Dissection Of Dog By Howard E. Evans, PhD 

Lecture no 4

BONES OF THE THORACIC LIMB(continued)

Veterinary Anatomy  GCVS 1st semester

Carpal Bones/Metacarpal Bones/Phalanges

Carpal Bones

The term carpus  is used to

designate that part of the extremity between the

antebrachium and metacarpus that includes all the

soft structures as well as the bones. The carpus in-cludes seven small, irregular bones arranged into

two rows. These are most conveniently studied

on radiographs. The proximal row contains three

bones. The largest of these, the intermedioradial

carpal(often referred to as the radial carpal), is on

the medial side and articulates proximally with

the radius. The ulnar carpalis the lateral member

of the proximal row. Its palmar portion projects

distally palmar and lateral to the fourth carpal

bone. The accessory carpal,the palmar member, is

a short rod of bone that articulates with the styloid

process of the ulna and the ulnar carpal bone andserves as a lever arm for some of the flexor muscles

of the carpus. The distal row consists of four bones

numbered from the medial to the lateral side. From

the smallest on the medial side, these are the first,

second, third, andfourth carpal bones.The fourth

carpal bone is the largest and articulates with the

base of the fourth and fifth metacarpals.

Metacarpal Bones

The metacarpus contains five

bones. The metacarpal bones are long bones in

miniature, possessing a slender body,or shaft,

and large extremities. The proximal extremity is

the base,and the distal one is the head.The meta-carpals, like the carpals and digits, are numbered

from medial to lateral. Proximally all articulate

principally with the corresponding carpal bones,

except the fifth, which articulates with the fourth

carpal. Distally all articulate with the correspond-ing proximal phalanges. Note the sagittal ridge on

the head for articulation with the sagittal groove

in the base of the corresponding proximal phalanx.

The interosseous muscles largely fill the intermeta-carpal spaces palmar to the metacarpal bones.

The first metacarpal bone is atypical. It is a ves-tigial structure, but unlike the first metatarsal bone

in the hindpaw, it is constantly present.

Phalanges

In the forepaw there are three phalanges for each

of the four main digits the first

digit, or pollex, a dewclaw, has two phalanges Each proximal and middle phalanx has a proximal

base,a body,and a distal head.

On the distal phalanx, a thin shelf of bone, the

ungual crest,overlaps the claw and forms a band

of bone around the proximal portion of the claw.

The ungual processis a curved conical extension

of the distal phalanx into the claw. The rounded

dorsal part of the base is the extensor processon

which the common digital extensor tendon is in-serted. A small process on the palmar surface is

the flexor tuberclefor insertion of the deep digital

flexor tendon.

Two proximal sesamoid bonesare located in

the interosseous tendons on the palmar surface of

each metacarpophalangeal joint (digits II–V). Four small dorsal sesamoid bones(none for the first

digit) are embedded in the common digital extensor tendons as they pass over the metacarpopha-langeal joints  

Posted in: 1st semester