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Two interesting muscles of mastication that are not found in most anatomy books.  

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auxiliary
Estimable Member

1) Sphenomandibularis, similar to the temporal muscle, however instead of producing movement upwards and backwards, it can produce movement upwards and forwards! It attaches to the internal oblique of the mandible and to the sphenoid bone behind the eyes.

What's interesting about this muscle is how high it attaches to the sides of the sphenoid, the medial pterygoids attach to the lower sphenoid(almost to the vomer) and even to the maxilla itself which means the medial pterygoids can't exert much force against the maxilla as they're pulling on it, but this muscle has such a high attachment that it can exert a lot of pressure on the maxilla upwards. Not only that, but this muscle literally attaches to the sphenoid right below the middle of the eyes, if any muscle can increase inter-eye distance, it has to be this one. It's also parallel to the maxilla from side-view.

2) Zygomandibularis, a very unknown muscle, I couldn't find any pictures of it, it may be absent in some people. Seems to be a hybrid between masseter and temporalis, it attaches to the anterior ramus and to the orbital part of the zygo/sphenoid bones. I did my best to try and draw it anatomically correct :

 

 I'd personally guess the function of this muscle is rotate the anterior of the mandible upwards while the posterior mandible remains stable.

 

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Posted : 23/05/2020 11:56 am
Azrael
Estimable Member

Nice find, how did you come across this?

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Posted : 23/05/2020 8:08 pm
Basim
Eminent Member

Seems like we are getting somewhere that muscles might be more important than mewing alone

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Posted : 24/05/2020 12:23 am
auxiliary
Estimable Member
Posted by: @basim

Seems like we are getting somewhere that muscles might be more important than mewing alone

Muscles of mastication were always important, even Mews said that.

Posted by: @azrael

Nice find, how did you come across this?

Randomly on the internet, I was researching other anatomy when some Indian slide on anatomy suddenly showed this muscle, I thought how strange it is that I've never heard of this muscle of mastication, then I researched it and apparently the muscle is relatively new and unknown. Then researching that muscle I came across the zygomandibularis which is an even more unknown muscle.

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Posted : 24/05/2020 7:00 am
Progress
Member Moderator

Great find, thanks for sharing. It seems that every piece in the craniofacial complex articulates with the sphenoid in one way or another.

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Posted : 24/05/2020 7:53 am
mr.mewing
Estimable Member

@basim I Agree with you man we are making big steps with this community

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Posted : 24/05/2020 8:47 am
Basim
Eminent Member

I believe with these muscles we can achieve CW rotation of the Sphenoid, which causes CCW rotation of the maxilla. Which in the thread of Progress Jaws Masseter vs Temporalis can theoretically lead the face become wider transversely and longer sagittally and get the facial upswing and open our airways.

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Posted : 24/05/2020 9:42 am
auxiliary
Estimable Member
Posted by: @basim

I believe with these muscles we can achieve CW rotation of the Sphenoid, which causes CCW rotation of the maxilla. Which in the thread of Progress Jaws Masseter vs Temporalis can theoretically lead the face become wider transversely and longer sagittally and get the facial upswing and open our airways.

There's not much evidence that the maxilla rotates at all, rather the lower part of the maxilla becomes more rounded and moves upwards. I don't think the face becomes much wider from mewing, instead it becomes visually wider because upper face becomes shorter. I also doubt the sphenomandibularis can affect the sphenoid in any form, the maxilla is simply a much weaker bone and will respond much faster than the sphenoid. I think this muscle may have the best attachments to shorten the maxilla in vertical height. I think because of it's position it can apply a lot of upwards force on the front teeth.

The sphenomandibularis is also very unique in that it's innervation isn't supplied by the same nerves that connect to other muscles of mastication, when these nerves are damaged the sphenomandibularis doesn't atrophy. Some books I've read about it say that it produces upwards anterior/lateral movement in it's attachment to the mandible.

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Posted : 24/05/2020 6:58 pm
auxiliary
Estimable Member

These muscles may also be of interest, though information on them is extremely limited, can't find anything except that they exist :

1) zygomaticomandibularis

2) maxillomandibularis

3) anterolateral muscle bundles(unnamed)

4) anteromedial muscle bundles(unnamed)

5) all kinds of other muscles documented, but unnamed, all over the place

I guess my point in this post is that :

  1. Unlike the masseters, which mostly put force on the posterior mandible and the temporalis which retracts the jaw and causes TMJ issues, there exist muscles that can provide upwards and forwards force for the anterior part of the mandible, which can be very effective for shortening of maxilla.

Of all the muscles, I think the sphenomandibularis is the most interesting one, it's pretty big, it's a mystery between an own muscle and a part of the temporalis, it's more commonly known as deep temporalis and since the temporalis is a postural muscle I think the sphenomandibularis may influence facial development by changing dental contact at rest.

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Posted : 24/05/2020 7:16 pm