What clues are your nails giving away about your health?
Many external parts of the body can reveal what is going on inside. This is not only true for your face and hair, but also your nails. Paying attention to your nails and any changes that take place in them can assist you in not only keeping them strong and healthy but this will also help you to address any potentially serious health issues before they escalate.
Nail Anatomy and Physiology
What exactly are nails?
Fingernails and toenails – we all have a set of each which consistently require frequent maintenance. We regularly trim and file them, and for those inclined to do so, paint and decorate them to suit our fancies too. How much do we really know about these bits of our bodies though?
You might know that nails are made up of a translucent protein known as keratin. Our hair and skin are also made up of this protein. Squamous cells at the base of the nailbed multiply, forming layers which harden. This growth process is known as keratinisation.
The hardened keratin layers are primarily useful for protecting the sensitive tissues at the tips of our fingers and toes. This helps to prevent injuries like scrapes and cuts which may occur while using our fingers and toes. The tissues at the tips (or pads) of our fingers and toes also contains sensitive nerve endings. These enable the fingers and toes to process sensations like ‘touch’. The nail acts as the vehicle for sensory input when contact is made between these portions of the body and other sources. Nails also provide support to these tissues. Without fingernails, we would struggle to be able to grasp or pick up objects or even have a good scratch. Nails are thus actually quite useful and functional, while also providing a canvas on which to decorate in order to make our digits more visually appealing.
How are nails structured?
The structure of nails consists of 6 key components, each with a function of their own. Any disruption or problem with these components can influence both healthy function and the appearance of our nails.
1. Germinal matrix (nail root)
This is where growth of the nail takes place – up to 90% of the nail is formed in the germinal matrix. (1) This portion is effectively the root of the nail which is located just below the skin beneath the nail.
2. Sterile matrix (nail bed)
Beneath the nail plate is the nail bed which consists of a dorsal roof, (topside of the formed nail) ventral floor (just beneath the formed nail) and capillaries (blood vessels) that provide blood flow. This is what gives the nail plate a slightly pink appearance.
The nail bed also consists of nerves and melanocytes which contribute to the production of melanin (the pigment that gives human skin, hair and eyes their colour). The dorsal roof houses the cells that contribute to healthy shine of the nail. The nail bed extends from the edge of the root to the hyponychium (near the tip of fingers and toes).
This region is susceptible to environmental contamination, and thus a ‘plug’ of keratin (containing polymorphonuclear leukocytes and lymphocytes, types of white blood cells that play a role in our immunity) serve as a barrier for protection.
3. Nail plate (body of the nail)
This is the most visible portion of the nail – it’s the bit that gets shaped and decorated. The point at which the nail plate seals with the nail bed near the tip of the finger or toe unit (also known as the distal or free edge – i.e. the skin portion at the tip) is referred to as the hyponychium. This also creates a waterproof barrier. Grooves along the length of the underside of the nail plate help to anchor it to the nail bed.
4. Lunula
At the base of each nail plate is a white / pale crescent (arc) shape known as a lunula. The paler colour is attributed to nail cell nuclei in the germinal matrix. There are no cell nuclei in the surrounding portions – hence the remainder of the nail has a more translucent appearance.
5. Nail folds – Lateral and proximal (known as the paronychium)
On either side of the nail plate and at the base, folds or skin grooves (or overlaps of skin) help to hold the nail plate in place.
6. Eponychium (cuticle)
A flap of thin tissue at the base of and overlapping the nail plate is more commonly referred to as the cuticle. This helps to fuse together the finger / toe structure and the nail plate, also providing a waterproof barrier.
How do nails grow?
Did you know? Fingernails can grow up to 3 times quicker than toenails! On average fingernails grow approximately 3 mm per month compared to toenails which grow 1mm every 4 weeks. (2) From the root of the nail to the edge of each finger, it can take around 6 months for growth to take place. For toenails, this growth process can take between 12 and 18 months. Growth of our nails is constant too, even if it tends to slow down as we age.
The nail matrix begins formation around the 9th embryonic week of life. Foetal nails are identifiable at around week 16. (3) As the majority of the nail plate is produced by the germinal matrix, the plate develops a natural convex curve (known as the gradient parakeratosis). The sterile matrix and dorsal roof of the nail fold also contribute to the production of the nail plate.
As squamous cells (i.e. the thin, flat cells that form the outermost layer of the skin) duplicate and enlarge (from both the germinal and sterile matrix), they migrate both distally and dorsally, forming a column. The duplication and enlargement process is referred to as macrocytosis and mostly takes place in the germinal matrix. Once the hardened, keratinised structure is formed, the squamous cells begin to incorporate themselves into the nail bed. From there the cells flatten and begin to elongate. The squamous cells in the sterile matrix also contribute to the thickness and strength of the newly formed nail plate.
References:
1. US National Library of Medicine - National Institutes of Health. May - August 2011. Nail bed injuries and deformities of nail: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3193631/ [Accessed 11.09.2018]
2. US National Library of Medicine - National Institutes of Health. 24 April 2010. Growth rate of human fingernails and toenails in healthy American young adults: https://www.ncbi.nlm.nih.gov/pubmed/19744178 [Accessed 11.09.2018]
3. Embryology - Dr Mark Hill. 25 October 2016. Text-Book of Embryology: The Development of the Integumentary System: https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_Text-Book_of_Embryology_16 [Accessed 11.09.2018]