Finger Nail Function
- Scratching
- Defense
- Efficient & accurate pick up of tiny objects
- Protection of finger tip
- Improves finger sensation - “Like cats whisker” - magnification of touch
- Regulation peripheral circulation & temperature
Anatomy
What you see is not the extent of the nail and nailbed.
There are 2 main components of the nailbed.
1. Germinal Matrix – is the base of the nailbed that extends to the Lunula
- Its function is to produce the nail
- It extends both on top of the base of the nail and deep to it
- pale pink or white in colour
- Damage can result in splits, troughs or irregularity in the nail
- a Mucous cyst can cause pressure on the Germinal matrix trough
2. Sterile Matrix – nailbed beyond the Lunula. Pink in colour
- its function is mainly adherence – it binds the nail down to the nailbed
- It also adds ~ 20 – 30 % thickness to the nail
- damage can result in loss of adherence of the nail. Dirt can get caught under the nail
Nail adherence
Nail Growth
• Nails grow at ~ 0.1mm / day
• Longer fingers faster
• Slow growth in paralysed fingers
Nail Growth after Injury
• Is abnormal for 100 days after injury
• 20 day delay after injury then the nail thickens proximal to injury
• 50 days it grows faster
• Then 30 days slower – thinner
Beau’s Lines
• Transverse Growth Arrest lines
• Sign previous illness - Eg serious febrile illness, Low blood pressure
• Distance can help date episode of illness
Eg an injury occurred 3 months ago
Subungual Haematoma
A crush to the finger tip can cause bleeding under the nail. It can be very painful due to the pressure of the blood. The pain can be relieved by drilling a hole through the nail with a needle under sterile conditions to release the blood.
It is important to make the hole big enough for the blood to continue draining. If not it risks closing over or getting infected. As the nail grows the haematoma moves down the nail. See below.
Nailbed repair
Stable skeleton
- The distal phalanx ( bone) is critical to support the nailbed and nail.
•
. If the tip of the finger is severely injured or amputated longterm nail deformity can result. ½ the length of the nail bed is required to prevent beaking of the nail.
