Cork and cork cambium (cork producing cell layer) are external Cortex-this is the primary tissue of the plant stem Phloem & Xylem are the inner most part and are concerned with carrying fluid and nutrients up and down the plant. Source(s): http://en.wikipedia.org/wiki/Bark. Orinoco Â· 9 years ago.
Malocclusion and bruxism are the most common causes of TMJ disorders. 1  Emotional stress is often the underlying cause of a TMJ disorder, as it can contribute to people either consciously or unconsciously tightening facial and jaw muscles and grinding or clenching their teeth.
The cause of TMJ disorders is not clear, but dentists believe it arises from problems with the muscles of the jaw or with the parts of the joint itself. Injury to the jaw, temporomandibular joint or muscles of the head and neck-such as from a heavy blow or whiplash-can cause TMJ disorders. Other possible causes include: 1  Grinding or clenching the teeth, which puts a lot of pressure on the TMJ. 2  Dislocation of the soft cushion or disc between the ball and socket.