So, it’s that time of year again when the pesky horse flies are upon us! , but did you know just how the horse manages to twitch parts of his skin to rid himself of these annoying parasites? 🧐
He is able to do this through a clever muscle called the Panniculus Carnosus, it’s the most superficial muscle in the horse’s body. It is part of the subcutaneous tissues and does not have a fixed shape or profile, just a thin muscular sheet like layer lying under the skin. Although this muscle does attach to some of the locomotor muscles, it’s action is completely independent of the locomotor system! Clever eh?!
So, when the horse’s sensory nerves are stimulated by a foreign object or a fly, this muscle receives the message and allows for independent movement of the skin and enable it to contract or twitch the skin, hopefully ridding itself of the pesky irritant!
It’s interesting to note that when rider’s legs are applied to the horse, one of their first effects are to stimulate the Panniculus Carnosus!
The horse eventually learns through his education to support unmoved the rider’s legs or spurs.
The Panniculus Carnosus does not cover the entire horse, so as you can see from my interesting hand drawn diagram 🙈, it does not cover the horse’s neck or lower legs and this is why you will see the horse shaking it’s head and neck or stamping bits feet to try and rid itself of any irritants in these areas!
Sources ~Henry L. de Bussigny-Equitation, Gillian Higgins- Horse Anatomy for performance, W.Frank Calderon-Animal Painting & Anatomy