For this month’s Fun Fact about your horse we are taking a look at the Panniculus Carnosus Muscle. This muscle is a very thin, subcutaneous,(i.e. lying just under the skin) flat, sheet like, muscle that is situated on the trunk of the horse. It runs from the base of the neck over the shoulders, back and quarters stopping just above the knee in the forelimb and just above the hock in the hind limb, see our diagram below showing the situation of this Muscle. The Panniculus Carnosus Muscle interlocks with the skin in the area of the trunk and is responsible for the movement of the skin in this area, causing movements such as puckering, twitching etc. It has an ingenious function and can be seen working beautifully during the summer months when it is responsible for the Fly Twitch Response/Fly Twitch Reflex.
The Fly Twitch Response occurs when a fly lands somewhere on the trunk of the horse and the sensory receptors of the hair and skin in the immediate area will send signals to the Panniculus Carnosus muscle causing it to twitch and vibrate to remove the invader. As this muscle is not present in the neck or lower limbs of the horse, horses will often shake their head in an attempt to remove flies from the head and neck and also stamp their feet if one of these awful pests land on their lower limbs.
If you are a Horse Owner no doubt you have witnessed the Panniculus Carnosus Muscle in action on a warm summer day, when the flies are at their worst. The slightest touch of one of these pests will set this muscle twitching. It is worth noting that lack of, or reduced reaction of the Fly Twitch Response can be an indication of a Neurological problem.
Why not take a look at our Video, in which we show you the Fly Twitch Response (also known as the Panniculus Reflex),in action with my own Horse and Equine Model Extraordinaire, Mr Ed.