A, C, E (TOP) ARE THE EXTERNAL VIEWS OF AN ADULT HUMAN, CAT, AND A JUVENILE HORSE, RESPECTIVELY. THE BONY CAP IS DEPICTED IN YELLOW, THE DISTAL PHALANX IS BLUE, AND THE MIDDLE PHALANX IS RED. B, D, F, G (BOTTOM) ARE CROSS-SECTIONS OF THE SAME SPECIMENS.
Research Alert
Newswise — In the late 1800s, researchers discovered, in separate studies, that horses and humans have a small bone at the tip of their hoof and finger, respectively. Since then, research on the anatomical development of many animals—including horses, humans, and other species—has forged on, but little attention has since been given to this bony structure, which went unnamed for more than 100 years.
Now, New York Institute of Technology College of Osteopathic Medicine (NYITCOM) researchers are resurfacing this small but mighty structure and ensuring that it does not become lost within the scientific literature. In a study published in PeerJ, they make the case for why this structure—which they dub “the bony cap”—may play a large role in digit (finger and toe) regeneration and nail growth.
The researchers analyzed the anatomy of fetal and adult humans, horses, and cats via microscopic tissue samples and scans obtained through micro-computed tomography (micro-CT), an imaging technique that captures microscopic images of specimens’ internal spaces and recreates virtual 3-D models without dissection.
They discovered that the bony cap was present on all digits in all three species, believing it to be a distinct anatomical structure during development that later fuses with an area at the tip of the digit called the distal phalanx. Their findings suggest that the bony cap plays a significant role in nail formation in humans, claw formation in cats, and hoof formation in horses. It could also impact similar formations in other species, though further studies are needed. In addition, the findings suggest that the bony cap may play a significant role in digit regeneration.
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