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The Anatomical Systems of the Horse and why we need to know about them

There’s no getting away from it – horses are truly amazing and as owners, riders, trainers, therapists and other equestrian professionals our aim is to ensure the horses in our care are happy and healthy. As their carers we must learn to ride sensitively, manage them effectively, learn to read their emotions and behaviour to ensure all their needs are met so they can thrive and perform at their best.


Having a thorough understanding of how the horse’s body works will go a long way to help us care for them to the best of our ability. Equine anatomy is fascinating - if a little complex, but don’t let that put you off. Gillian Higgins is here to help guide you through the world of equine anatomy and make it easy to understand.


"In 2011 I challenged myself to illustrate every part of every anatomical system of the horse, on the horse... and not just by painting the structures on the side of the horse but where appropriate, from in front, behind and above too!"

From this mission Horse Anatomy for Performance and the Horses Inside Out Anatomy Poster Books (Volume 1 covers the musculoskeletal system and Volume 2 is the internal organs. ) were born. As these three books celebrate 11 years since they were published, we thought it we would take a closer look at them and the anatomical systems behind them to discover why this information is must for anyone interested in horses.




"Having recently visited Media Book Service in Holland it was great to learn how much my books are appreciated over there. Horse Anatomy for Performance is a firm favourite with the equestrian colleges and universities as it is such a great way for students to learn about the anatomical systems. " says Gillian.



"Did you know there are 11 anatomical systems in the horse?"

In this article there is a brief summary and interesting fact about each, but in Horse Anatomy for Performance - A Practical Guide to Riding Management and Horse Care' there is a detailed chapter for each system illustrating every aspect of the system and explaining how anatomy influences the way we ride, train and manage our horses.

When Gillian was writing this book, she kept asking herself, ‘Why does the horse owner need to know about this system?’ By constantly asking herself this question means this book has a real focus and relevance, providing you with the key information you need to know about each system and how they work together and independently.

1. The Integumentary System (the skin)

The skin is the largest and heaviest organ in the horse’s body. It is a highly sensitive organ covered in three different types of hair:

  • Permanent hair – the mane, tail and feathers

  • Tactile hair – whiskers, used to estimate the distance between the muzzle and an object

  • Temporary hair – his coat consists of an undercoat of fine, densely packed hairs, covered by a layer of longer coarser hairs

Directly underneath the skin there is superficial fascia which in some places more than others has direct connections to the rest of the fascia system deeper within the horses body.


This is one reason why simple skin movement and basic myofascial release techniques can be so effective with horses. This is something Gillian talks about in great detail in the online massage course.



2. The Skeletal System


The skeleton consists of approximately 205 bones (this number can vary as some bones fuse together). It can be divided into the Axial skeleton – made up of the skull, vertebrae and ribs, and the Appendicular skeleton which comprises of the limbs.


The skeleton is something that Gillian has painted on horses hundreds of times - each time as accurately as possible related to their skeletal landmarks and conformation - and not just from the side but in front, behind and above too. These paintings are all clearly labelled with the simple common English as well as the more advanced Latin names in Anatomy Poster Book Volume 1 - making it perfect for the equestrian student.


3. The Muscular System (this includes, tendons, ligaments and fascia as well as muscles)


Muscles create and allow every aspect of movement – both internal and external. They form the largest tissue mass in the horse’s body and are surrounded by and connected together via fascia. Tendons connect muscle to bone and are involved in transferring forces for movement whereas ligaments connect bone to bone to support and control joint movement.


There is lots of opportunities to learn about the muscles, tendons, ligaments and fascia in the Horses Inside Out Academy.



4. The Digestive System


Horses have a unique digestive tract that can digest both forage and concentrates. with different structures on the left and right sides of the abdomen it took multiple paintings to illustrate this system. Paintings for this project included the digestive tract on the left and right sides and separate paintings to show the location and size of the liver and pancreas.


The anatomy of the gastrointestinal tract and the implications for feeding and management is also something Gillian looks at in great detail in the on-demand seminar Digestive Anatomy, Feeding and Nutrition as well as in her book Horse Anatomy for Performance.



5. The Nervous System


The nervous system includes the central nervous system: the brain and spinal cord and the peripheral nervous system: the network of sensory and motor nerves. In addition to illustrating these Gillian also explains the dermatomes.


“I love the dermatomes painting in volume 2,” says Gillian. “I did this using chalk rather than paint, which is unusual, but this one also brings a smile to my face each time I look at it. We lost Freddie in 2021 and it’s memories like this that remind me how Freddie really was and continues to be the face of Horses Inside Out. When I look at this picture, I think of Freddie wearing his pyjamas!”

Understanding Dermatomes

A dermatome is a surface area of the body served by a specific nerve or group of nerves – this image is like a map of the dermatomes in the horse’s body. We have dermatome maps for people as well. But what are dermatomes and why are they important?


Think about this in humans first. If you have a tingling in your ring finger, it may not be your finger that's injured the sensation could be coming from your eighth cervical nerve, which is right at the bottom of your neck. Essentially, the cause, and the place where the symptoms are, aren't necessarily in the same place.


Applying this to horses can be a little tricky but you can look out for signs- such as seeing a change in the quality of the skin, sweat patches, and most interestingly, when you get a really localised area of muscle atrophy - of course it could be there's nerve damage to that area, but it could also be coming from further away. This is why diagnosing a problem can be so challenging.


Learn more about the anatomy and function of the brain as well as training and behaviour in the fascinating on-demand seminar with Dr Andrew Hemmings: Training the Brain.




6. The Circulatory System


Understanding the circulatory system is so important for training and fitness. To fully illustrate the circulatory system for this project required 6 different paintings!

  • The heart

  • The heart in location with the lungs

  • The main arteries

  • The major veins of the horse

  • The size and location of the spleen

  • The places it is possible to take the horse's pulse

These are all explained in full in Horse Anatomy for Performance and the Horses Inside Out Anatomy Poster Books Volume 2.



7. The Lymphatic System


Closely linked and connected to the circulatory system, the lymphatic system helps to drain the tissues of fluid and cleanse the fluid before returning it to the bloodstream. Understanding more about the lymphatic system can help us appreciate the importance of regular movement, how to reduce swelling, understanding infection and how the body deals with it and works to prevent it happening.


8. The Endocrine System


Hormones have a massive effect not only on the body's ability to function but also on behaviour, health and performance. This system is often forgotten about until there is a problem (for example equine metabolic syndrome or Cushing's) but all riders and trainers would benefit from a basic understanding about the endocrine system due to its effect on the horse's ability to train. Understanding it can help us to improve the effectiveness of our training and fitness methods. Learn more in Horse Anatomy for Performance.


9. The Respiratory System

It's not just about the lungs! Gillian used paintings of the the pharynx and trachea to effectively illustrate how different head and neck positions affect air flow and intake and the position of the diaphragm from the side and above and it's relationship with the hind gut to help illustrate how and why coupled breathing works in canter.


Anyone who wishes to improve the fitness of their horse needs a thorough understanding of this system. Also, we know the effect that breathing can have on our own emotions and state of calm, and the same can be applied to the horse.


10. The Urinary System

Why do we need to even bother to learn about this system? The urinary system is not just about the bladder and expulsion of urine but also and most importantly the regulation of hydration. Hydration is key to a healthy body and effectively functioning tissues. Muscle and fascia (as well as all other systems) need to be hydrated to perform well. This is something discussed in more detail in Horse Anatomy for Performance.


11. The Reproductive System

"I had so much fun with the paintings to illustrate the reproductive system, particularly when painting Freddie in foal!"

For anyone with horses, and not just those interested in breeding, a basic understanding of the reproductive system and the influence the relevant hormones have on the horse's ability to function and train as well as the effect on the fascia and connective tissues is useful for improving training and helping to reduce the risk of injury.


We love to hear your feedback on these blogs, so if you have any comments, please post them below. Also, if you have any ideas for future blogs let us know by emailing your suggestions to - admin@horsesinsideout.com




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