- The 2nd and 4th metacarpal/metatarsal bones in horses are remnants of toes from a paw-like structure. Early horse ancestors had multiple toes, spread out with soft pads, like those of small mammals. These toes were suited for walking on soft, forested ground. As horses evolved into larger, faster runners adapted to open plains, their limbs streamlined, and the number of functional toes decreased. The middle toe (the 3rd metacarpal/metatarsal) developed into the strong, single hoof seen in modern horses, while the other toes became the vestigial splint bones.
- The horse’s knee is equivalent to our wrist, the hock is similar to our heel, and the stifle corresponds to our knee.
- Muscles attach to bones through fascia at bony protuberances such as crests, tubercles, tuberosities, ridges, lines, epicondyles, consoles, trochanters, or processes.
- Nerves and blood vessels pass through bones via foramina (singular: foramen), which are small openings in the bone, or through canals and fissures, depending on their size and location. These structures allow them to travel to various parts of the body while being protected by the surrounding bone.
- Navicular bones are small, boat-shaped bones located in the front feet, at the back of the coffin joint, between the short pastern and coffin bones. They provide a smooth surface for the deep digital flexor tendon to glide over, reducing friction as the tendon flexes the hoof. Navicular bones also help stabilize the coffin joint and absorb the impact forces generated when the horse’s hoof strikes the ground, distributing pressure during movement.
- New research indicates that the bone-derived hormone osteocalcin, not adrenaline, drives the fight or flight response. When the brain recognizes danger, it instructs the skeleton to release osteocalcin into the bloodstream, preparing the body to react swiftly.
- Bones are not merely rigid structures; they possess elastic properties and function as compression springs. They absorb and manage forces by storing energy when compressed, providing resistance and support, and returning to their original shape when the load is removed, and releasing the stored energy. Research on stress-strain curves shows that bones, similar to a pogo stick, handle loads better with increased speed. Bones are not compressed in only one direction; they are surrounded by soft tissues that provide uniform compression, ensuring even loading.
- Osteocytes, the cells responsible for maintaining bone, form a network within the bone tissue by extending long, thin projections through tiny channels called canaliculi. This sensitive network allows mechanical strain detected in one area to be communicated across the entire bone, enabling the bone to respond and adapt to stress.
- Bones act as levers and joints serve as fulcrums, enabling movement when muscles contract. In a tensegrity model, bones are often referred to as ‘tent poles,’ providing structural support, while the muscles and fascia maintain flexibility and balance within the system.
- The sympathetic nervous system has a more complex and widespread presence in bone tissue compared to the parasympathetic system. Its activation, especially during stress, suppresses bone growth by inhibiting the activity of bone-forming cells (osteoblasts). This means that long-term (chronic) stress can negatively impact bone growth and maintenance in your horse, potentially affecting their overall health and soundness.
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