Different Types of Muscle Fibre Arrangements

So we all know that muscles help create movement; but there are other roles within our horses body that muscle have a part in.

For instance cardiac muscle; it is super thick and can therefore withstand a high pressure allowing blood to enter and exit the heart.

Next, we have smooth muscle that is found within and surrounding our internal organs.

Many of our bodily functions are carried out involuntarily; thanks to the autonomic nervous system!

Same for your horse! Smooth muscle is what allows for feedstuff to travel through the digestive tract and for waste products to be excreted the other end (either as urea or faeces)… without thinking about it – magical!

However, the vascular system also consists of smooth muscle, as does the reproductive system.

That now brings us to the main muscle group we are going to discuss today – skeletal muscle.

There are over 700 different skeletal muscles in the horses body (Higgins, 2012)

Yes, they do create movement – that is probably the most obvious function however, how often do we think about energy being expended through the horses’ muscles for the following….

* To support and protect the skeleton

* To allow for joint stability

* To aid postural support

* To help with thermoregulation

* To act as bubble wrap against potential trauma (particularly to the internal organs!)

Pretty amazing how much muscles contribute to bodily function aside from creating movement, this is why it is so important to keep a check on our horses musculoskeletal system; as there could be more going on than what meets the eye.

So muscle formations….let’s have a dabble into that now we have covered some of the functions of muscles.

Postural and skeletal muscle with supportive properties is often found on a deeper level in comparison to superficial muscles.

Superficial muscles – the ones you can physically touch/are closer to the surface are typically involved in movement.

However, there is some overlap of course – as unlike textbook diagrams; all of the muscles, connective tissue and fascia (which is also technically connective tissue) are all intertwined and connected to one another…

And do not just peel off in nice neat layers…

Try doing a dissection – trust me it is a skill to isolate each layer individually without cutting into another!

Now remember different muscles have different functions; so therefore their formation (i.e. how they are configured) will differ to allow them to operate in the way that is best suited for their job role.

So let’s take the Ventral Serratus a.k.a The Ventral Serrated muscle a.k.a The Ventral Serrate (yes, I know… why the authors of these anatomy books couldn’t just agree on a fixed name to make it easier I don’t know!)

Any-hoo! This is a huge muscle that has a cervical portion and a thoracic portion.

The purpose of this muscle is to suspend and move the thorax in relation to the horses legs … so in other words when the muscle contracts it raises the chest relative to the shoulder blades (Nikkel, 2012).

So when you’re leading your horse; and they suddenly stop and gaze into the distance snorting at a cloud, and grows to be like 17hh…. Yeah those ventral serratus muscles are doing their job just fine!

So the bottom edge of this muscle looks serrated – hence the term serratus

Ventral/Ventralis whatever you choose to call it – just remember ventral means lower/underside.

And it is what we call a Multipennate muscle formation and resembles feathers (but imagine lining up several feathers in a row) the feather fibres are a bit like the muscle fibres branching out from the central tendon; each central tendon then joins on to common tendon that they all share. [See diagram below - where it says Multipennate]

I assume the picture explains better than the words!

Now supporting the entire thorax is a pretty huge job… so these muscles are pretty dang strong!

Not only that, but the muscle fibres need to span quite a significant distance along the body to get the job done!

And it is their Multipennate formation that assists with their purpose.

Obviously, muscles don’t just work independently; other muscles will help with this task.

Other muscle formations include: Triceptal, Fusiform, Pennate and Parallel (please see diagrams as above!)

Coincidentally, the ventral serratus muscle is part of the thoracic sling group of muscles, which is handy as I can now discuss a few of the other muscles related to keeping the forelimbs attached to the horse.

Works Cited

Higgins, G. (2012). Horse Anatomy for Performance: A Practical Guide to Training, Riding and Horse Care. Exeter: David and Charles Ltd 2012.

Nikkel, R. (2012, July 14). The Serratus Ventralis Muscle. Retrieved from Rod Nikkel Saddle Trees: www.rodnikkel.com

*Please note: Although the diagrams aren't great! I have drawn them myself to avoid copyright infringement - if you use them please be sure to cite me as the original author thank you!*