Nail Lunula

The lunula (half-moon) is the whitish, opaque area at the base (proximal end) of the nail plate. The plump, white keratin cells flatten like pancakes. When they flatten, most of the material inside the cell is lost. This is why the cells become transparent. The lunula is formed by cells that have not yet completely flattened or lost their inner material. Not all fingers have a lunula. On fingers with a lunula, the front end of the matrix is directly below the whitish area. The h u l a outlines the front part of the matrix. The lunula is usually seen on the thumb and index finger. Interestingly, you can tell if a person is right- or left-handed by which thumb has the largest lunula. The thumb with the largest lunula is on the dominant hand.

The lunula also determines the shape of the nail plate. Look at the shape of your lunula and compare it to the natural shape of the nail plate’s free edge. They are an identical match. Both the lunula and free edge are crescent shaped. As mentioned above, it is also the shape of the distal (front end) part of the matrix. Animals with different-shaped lunulas have nail (or claws) which also match in shape. Figure 1.3 shows the claw and lunulas hapes of six different types of primates.’ Notice that the shape of the lunula closely matches the free edge.