Page 40 - 84 human physiolofy part-1

Chapter 3

Nails

Parts of the fingernail

The fingernail is an important structure made of
keratin. The fingernail generally serve two purposes. It
serves as a protective plate and enhances sensation of
the fingertip. The protection function of the fingernail
is commonly known, but the sensation function is
equally important. The fingertip has many nerve
endings in it allowing us to receive volumes of
information about objects we touch. The nail acts as a
counterforce to the fingertip providing even more
sensory input when an object is touched. The parts of a finger nail

Nail Structure

The structure we know of as the nail is divided into six specific parts - the root, nail bed, nail plate,
eponychium (cuticle), perionychium, and hyponychium.

Root The root of the fingernail is also known as the germinal matrix. This portion of the nail is
actually beneath the skin behind the fingernail and extends several millimeters into the finger. The
fingernail root produces most of the volume of the nail and the nail bed. This portion of the nail does
not have any melanocytes, or melanin producing cells. The edge of the germinal matrix is seen as a
white, crescent shaped structure called the lunula.

Nail Bed The nail bed is part of the nail matrix called the sterile matrix. It extends from the edge
of the germinal matrix, or lunula, to the hyponychium. The nail bed contains the blood vessels, nerves,
and melanocytes, or melanin-producing cells. As the nail is produced by the root, it streams down
along the nail bed, which adds material to the undersurface of the nail making it thicker. It is important
for normal nail growth that the nail bed be smooth. If it is not, the nail may split or develop grooves
that can be cosmetically unappealing.

Nail Plate The nail plate is the actual fingernail, made of translucent keratin. The pink appearance
of the nail comes from the blood vessels underneath the nail. The underneath surface of the nail plate
has grooves along the length of the nail that help anchor it to the nail bed.

Eponychium The cuticle of the fingernail is also called the eponychium. The cuticle is situated
between the skin of the finger and the nail plate fusing these structures together and providing a
waterproof barrier.

Perionychium The perioncyhium is the skin that overlies the nail plate on its sides. It is also
known as the paronychial edge. The perionychium is the site of hangnails, ingrown nails, and an
infection of the skin called paronychia.

Hyponychium The hyponychium is the area between the nail plate and the fingertip. It is the
junction between the free edge of the nail and the skin of the fingertip, also providing a waterproof

40 | Human Physiology