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Equine Reciprocating Systems Series: Interosseous Muscles to the Suspensory Apparatus

In this second in a series, Dr. Deb Bennet continues a discussion of the horse’s forefoot becoming a single digit.

Farrier Takeaways

  • The anatomy of the forelimb of each kind of mammal dictates its overall movement style.
  • Skeletal changes that contributed to the horse’s survival in open country include unguligrade stance and “telescoping” – proportional lengthening – of distal limb elements.

In the first installment of this series on the anatomy and function of the forelimb reciprocating apparatus in horses (September/October 2019 American Farriers Journal), I discussed the many differences between white vs. yellow ligament tissue. In this installment, we focus on the relationships between muscles, the tendons of muscles, and yellow ligaments.

In his Atlas of Equine Anatomy for example, veterinarian Chris Pasquini correctly labels the suspensory apparatus found in the legs of horses as “interosseous (suspensory lig.)” Developmental studies have shown that the suspensory apparatus, composed as it is of yellow ligament, was once a group of muscles.

When Mr. Spock from the Star Trek series gives the Vulcan sign for “live long and prosper” by making a “V” between his middle and ring fingers, he’s using muscles (the interossei and lumbricales) that anchor between the metacarpal (palmar) bones. Although their fossil ancestors once possessed the full complement of five digits as we humans do, our modern horse, belonging to the genus Equus, possesses but one digit per limb — that’s one shy of what would be needed to make a “V.”

Next in Series:

If you want to follow up in more depth concerning the evolution of the horse, please go to Dr. Bennett’s Equine Studies…

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Dr_deb_bennett

Deb Bennett

Dr. Deb Bennett has studied classification, evolution, anatomy and biomechanics of the horse. She worked at the Smithsonian Institution, until founding the Equine Studies Institute. She is an author who has published four books on horse-related topics, in addition to articles in most major equine magazines in North America.

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