Temporal Fenestra

In Biology we were talking about the succession of creatures in the fossil record and the emergence of mammals, and my teacher pointed out that all mammals have a temporal fenestra.  I had no idea what that is but inferred it's one of the holes in the skull near the temporal bone.

Except that didn't make sense because all the "holes" there have nerves and vessels coming through them, not muscles, but the book said the temporal fenestra is the portal for the cheek muscles.  I was determined to figure out where ours is.

So, being the smart cookie that I am, I figured out that it had to be the zygomatic arch.  (The "hole" made between the zygomatic arch and the rest of the skull).  And I didn't even look it up online. :)

The masseter muscle and temporalis muscle go behind the zygomatic arch down to the mandible and do their thing for mastication (that's chewing for you non-science types).

Site this pic is from

I added the dorky little arrows to show you the zygomatic arch.  This drawing just has it cut away, so those are the two cut edges- the arch connects between them.  FYI, the zygomatic bone is the one that makes your cheekbone.  The temporalis muscle originates in the temporal fossa of the skull.  If you clench your teeth and feel the side of your head at the temples you can feel it flexing.  It inserts on the medial side (inside) of the mandible.

The masseter muscle actually originates on the medial side of the zygomatic arch itself and inserts roughly the same place as the temporalis muscle.

So there ya go...mastication muscles go behind the zygomatic arch - our temporal fenestra. :D