Why are human beings able to move their lower jaw while talking and chewing, but cannot move their upper jaw?

Why are human beings able to move their lower jaw while talking and chewing, but cannot move their upper jaw?
  1. The upper jaw is joined to the skull by an immovable (fixed) joint
  2. The upper jaw has a hinge joint that opens upwards
  3. Muscles are attached only to the upper jaw
  4. The upper jaw is made of cartilage instead of bone

Solution

The upper jaw is fused to the skull bones via immovable (fixed) joints, making movement impossible.

Asked in: Homi Bhabha Practice

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