Vocal Fold Anatomy: Body Cover Model

The vocal folds are made up of a body and cover. The vocal folds consist of several layers:

1. The outer cover (epithelium)
2. The middle layer (lamina propria)
3. The body (vocalis muscle)

The middle layer is also divided into three more layers:

1. The superficial layer of the lamina propria
2. The intermediate layer of the lamina propria
3. The deep layer of the lamina propria

There are various modes of vocal fold vibration. Each of these modes is believed to be dependent on the degree of coupling between the three main layers (epithelium, lamina propria, and vocalis muscle). The difference in stiffness among these three layers will be responsible for the mode of vibration and resultant sound the vocal folds produce. For example, in a pathological vocal fold, the pathology may create stiffness, thus altering the bio-mechanics of the vocal fold tissue and a change in the way they oscillate. This change may be responsible for dysphonia (the perceived change in vocal quality).