Saturday, April 23, 2011

Bone Examinations

Observations of the Intermaxillary Bone

Reading Goethe’s piece “An Intermaxillary Bone Is Present in the Upper Jaw of Man as Well as in Animals” was interesting, but it was frustrating to not be able to see the bones of which he was speaking. Considering I had never handled a human skull to observe the bones in the jaw, I could not imagine the differences he was describing. It was very interesting and rewarding to be able to observe these things for myself at the Exhibit Museum of Natural History.

I observed most of the skulls that were laid out, but I was most interested in the human skull versus the skull of the chimpanzee and the skull of the gorilla. These were my most detailed drawings, and I spent the most time finding different comparisons I could make.

I first compared the skull of a mature chimpanzee with that of an adolescent chimpanzee. The most obvious thing I observed was the difference in the distance between the nose and then tip of the mouth. After comparing the intermaxillary bones in each, I decided this was not the source. The intermaxillary bones were proportionally equal in size. In the adolescent chimpanzee, the molars start right beneath the nose. However, in the older bone the molars start much further forward, accounting for the lengthened snout.

I then observed the gorilla and human skull. The most striking difference between the gorilla and the chimpanzees was the alignment of the first four teeth. This is due to the curvature of the intermaxillary bone. In the chimpanzees the front four teeth are curved, more like the humans. In the gorilla, the front four teeth are aligned almost completely straight. I found it interesting that the curvature in the intermaxillary bone in the chimpanzees were more similar to the humans than the gorillas. However, in the human skull, the intermaxillary bone is located almost directly beneath the nose. This is not the case in the chimpanzee or the gorilla, in which the intermaxillary bones are located a good amount past the nose.

I also observed that the palates in the chimpanzee were very shallow in comparison with the gorilla and the human. The human skull had the deepest palate of all however. In researching the function of the palate, I discovered the hard palate is responsible for the formation of sounds, particularly the “t”, “d”, and “j.” This could explain the differences in the concavity of the palate. Since the human skull had such a deep palate, this may be due to the ability to make these sounds in speech, something less important for gorillas and chimpanzees.

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