As an equine massage therapist I’ve spent a lot of time studying equine anatomy and physiology. And through that process I have grown to have a special appreciation for the kidneys – those little lopsided organs that work so tirelessly filtering the blood (the left kidney is typically slightly larger, and sits a little closer to the spine than the right).
But what do the kidneys have to do with equine massage?
Well, for one thing you need to be cautious not to massage too deeply over the horse’s loin area where the kidneys lie, only partially protected by the end of the rib cage. Unlike most of the other organs, which are safely tucked away inside either the thoracic or abdominal cavity, the kidneys are retroperitoneal – which is a fancy way of saying they are outside of and behind (retro) the peritoneum – the membrane lining the abdominal cavity.
And therein lies the first clue as to why the kidneys, as an organ, are so neat. (They also, I will add, even have a similarly shaped bean named after them).
On the outside of the abdominal cavity membrane, the kidneys lie in very close proximity to the important psoas muscles, those powerful hip flexors that run along the underside of the lumbar spine, through the pelvis and attach to the inside of the femur (thigh) bone. The psoas muscle also plays an important role in supporting and stabilizing the lumbar spine during movement and is closely linked, via the connective tissues, to the lumbar plexus – the biggest nerve centre of the hindquarters. Altogether it’s a very interesting area in the horse’s body, both functionally and physiologically.
But it’s not just their physical locale in the body that sets the kidneys apart. From the early stages of embryonic development the kidneys take a less travelled path – at least compared to the other major organs. During development in the womb, the kidneys actually share more in common with another part of the horse’s anatomy for which I have a personal affinity – the connective tissues.
During early embryonic development there are three layers of tissue from which all the various parts of the body – heart, lungs, bones, brain, skin, etc – are eventually formed. The ectoderm, the outermost layer, develops into the brain, nervous system and skin. The internal organs come from the innermost layer – the endoderm. And then there’s the middle layer, the mesoderm, which forms the all the connective tissues in the body – the bones, cartilage, joint capsules, muscles, tendons, ligaments – and the kidneys.
Then there’s also the adrenal glands that sit atop the kidneys, which are pretty interesting in their own right, responsible as they are for orchestrating the “fight or flight” response in part through the release of adrenaline (epinephrine) directly into the blood stream. As part of the endocrine system, these glands help regulate a number of the body’s functions through the production and secretion of hormones and chemicals. Among other things, the adrenal glands also produce cortisol (a steroid hormone) in response to stress, which if sustained can in turn affect the health and integrity of the connective tissues.
I’ll admit I never cared much about biology until I started studying it in the horse. But it’s the kind of thing that once you care enough about it to learn about it, and learn enough to become sufficiently impressed by it, you can really develop a renewed appreciation for those body parts, like the kidneys, that you’ve always known something about but never really give much thought to. Or maybe that’s just me…