Before birth, the palate begins as two divided shelves of tissue. The shelves grow toward each other and eventually join in the midline. ("Midline" refers to an imaginary line that divides our bodies into left and right halves.) There is muscle within these shelves; when the shelves join, the muscles interdigitate (interlock).
If the shelves fail to join, the child is born with a cleft palate. When the shelves join but the muscles fail to interdigitate, the child is said to have a submucous cleft palate. In other words, below the mucous membrane, the muscular portion of the palate is still separated. Frequently, bifid uvula is a clue to the presence of a submucous cleft palate.
Interdigitation of the muscle is important to the palate's function, so submucous cleft palates are inefficient compared with normal palates. This can cause problems with speech, swallowing and eustachian tube function (leading to frequent ear infections).