Veterinary Gross Anatomy

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

Ox

First phalanx / os suffraginis

• It is a long bone placed obliquely downward and forward between the large metacarpal above and the second phalanx below.
• The shaft is four sided.
•  The dorsal face is convex and blends with the abaxial.
• The volar face is flat and presents two tubercles, one on either side about the middle of its borders for ligamentous attachment.
• The axial face is flat.
•  The proximal extremity is larger than the distal. Its articular surface is divided by a sagittal groove into two areas (the abaxial being the larger and higher), which respond to the distal end of the large metacarpal and behind these are two facets for the proximal sesamoids. On the volar aspect are two tubercles for ligamentous attachment.
•  The distal extremity is smaller. Its articular surface is divided by a sagittal groove into two condyles (abaxial being the larger) which respond to the proximal extremity of the second phalanx.

Second phalanx /os coronae

• It is a long bone placed obliquely downward and forward between the first and third phalanges. The distal half of each is included within the hoof.
• The shaft is three sided.
• The volar face is encroached on by the distal articular surface.
• The abaxial face is rough while the axial face is flat.
• The proximal extremity is made up of two glenoid cavities, the abaxial of which is the larger. The volar aspect presents two tubercles for the attachment of the superficial flexor tendon.
• The distal extremity is smaller and is divided by sagittal groove into two condyles, the abaxial being the larger. It articulates with the superior face of the third phalanx below and the distal sesamoid behind.

Third phalanx / os pedis

• It is a short bone entirely enclosed in the hoof.
• It presents four surfaces and an angle.
• The superior face is articular and presents two areas for the distal extremity of the second phalanx and a small facet along the volar border for the distal sesamoid.
• The inferior face or solar surface is nearly flat, wide in the middle and narrowest in front. It is in contact with the sensitive sole in life.
• The interdigital surface is smooth and grooved below and rough and porous above. It presents a large foramen near the extensor process, the volar foramen.
• The laminar surface slopes from above downward and becomes steep posteriorly. Distally it is traversed by the preplantar groove with several foramina; the most posterior of these is the largest. The surface is covered by the sensitive lamina in life. At the extreme upper part of the dorsal border is the extensor process for the common digital extensor. The volar border is thick for the attachment of the deep flexor of the digit. The angle is a blunt process at the extreme posterior part of the laminar surface.

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Sheep and Goat

• Similar to that of ox.

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Horse

• Each phalanx appears like the combined corresponding phalanges of the ox.
• First phalanx, the volar face presents a “V” shaped area beginning from the proximal tuberosities and converging distally, which furnishes attachment to the distal sesamoidean ligament. The proximal face is articular and is divided by a sagittal groove into two concave areas, the medical being the larger. The lateral face bear tubercles.
• Second phalanx is a short bone being more wide than long.
• Third phalanx has three surfaces, three borders and two angles. The superior articular surface is adapted to the distal extremity of the second phalanx and distal sesamoid. The volar face is divided by the semilunar crest into a larger concave solar surface and smaller semilunar flexor surface. The latter presents a central prominent area on either side of which is the volar foramen, which leads into semilunar canal within the bone. The crest and the prominent area furnish attachment to the deep flexor tendon. The antero-superior or coronary border bears about its middle the extensor process or the pyramidal process for the common extensor tendon. The postero-superior border is nearly straight and forms the posterior limit of the superior articular surface. The distal border is irregularly notched with a wider notch in front. The angles or wings project backward and are divided into upper and lower parts by a notch or a foramen. The proximal border of the angle carries the cartilage of the third phalanx.

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Pig 

• Each digit has three phalanges.
• The phalanges of third and fourth are well developed.
• The phalanges of second and fifth digit are small and generally donot reach the ground.
• There are two proximal and distal sesamoid bones in each digit.

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Dog

•  The first digit has two phalanges and the other digits have three phalanges each.
• The first phalanges of the chief digits have four sided shafts and the second phalanges about two thirds of the length of the first phalanges and their distal extremities are wider and flatter than those of the first.
• The third phalanges correspond to the shape of the claws.
• The proximal face or base responds to the second phalanx.
• It is encircled by a collar of bone with which it forms a groove into which the proximal border of the claw is received.

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Rabbit

• The first digit has two phalanges and the remaining four digits have three phalanges each.
• All the 3 rd phalanges bear horny claws.

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Fowl

• The first and second digits have two phalanges each.
•  The third has only one phalanx.

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