The Hair

Nails provide some protection to our sensitive fingers and toes as well as allowing us to grasp small objects

The nail is made up from the following: –

Nail Wall: This is the folds of skin that overlap the sides of the nail. It holds the nail in place and protects the nail plate edges.

Matrix: The only living reproducing part of the nail, this is situated directly below the cuticle. New cells form here and continually push towards to produce the nail plate. It also contains blood vessels and nerves. Blood supply provides the cells with nourishment. If the matrix is damaged the nail will grow deformed.

Lunula: (Halfmoon) This is the meeting point for the matrix and nail bed and is pearly coloured and crescent shaped due to the cells being pushed closely together. The blood capillaries cannot be seen through the lunula because of this.

Nail Plate: Visible nail that rests on the nail bed up to the free edge. This is made up from dead cells (that have been pushed up from the matrix) and are held together with a minimum amount of moisture. The nail is semi-transparent – allowing the colour of blood supply of the dermis to show through (pink colour).

Nail Bed: Part of the nail that the nail plate rests on, also a continuation of the matrix. It is abundantly supplied with blood vessels and nerves, having numerous parallel ridges which dovetail exactly with the ridges on the under surface of the nail plate.

Free Edge: Is an extension of the nail plate. It overlaps the hyponychium. This part of the nail can be filed and shaped.

Cuticle: This is the overlapping epidermis surrounding the nail. It protects the matrix from invading bacterial and physical damage.

Eponychium – Base of the nail.

Perionychium – Sides of the nail.

Hyponychium -The portion of the skin at the end of the finger which is underneath the free edge.

Nail Grooves (Or furrows): Side of the nails upon which the nail moves on and acts as a guideline for the nail to follow.

Mantle: Is the skin over the matrix which protects it.

Disease or Disorders of the Nail

There are a variety of diseases that can affect the nail, ranging from anonychia, which is a congenital abnormality in which there is an absence of a nail, koilonychias, where the nail becomes spoon shaped, onycholysis, which is where the nail becomes separated from the nail bed and paronychia, in which there is a bacterial infection of the cuticle. Nails can also become curved, shed or ingrown.

Nail Pathologies

NameAppearanceCause
LeukonychiaWhite flecks within the nail plate.Trauma to the nail or signs of a disease.
Hang nailA small piece of torn skin next to the nailUsually picking or biting the nails
ParonychiaSkin infection around the nails, causing red swellingFrom biting or injury
Vertical ridgesLines running the length of the nailUnknown but more common as you get older. Nothing to worry about
OnycholysisSeparation of the nail from the bedUsually trauma but can be a sign of disease

Diagram of the Structure of the Nail

Glands

There are two types of glands that are associated with the Integumentary system. They are sweat and sebaceous glands, and both have their own different roles. There are around 2.5 million sweat glands covering the majority of the body and these consist of eccrine and apocrine sweat glands. The eccrine sweat glands produce a clear secretion with is made up of 99% water. The other 1% consists of salts and traces of waste. These glands are found all over the body but have a large supply on the forehead, upper lip and palms. The apocrine sweat glands are larger and do not function until puberty. They are found in the armpits and groin and secrete a cloudy substance which contains proteins and fatty acids. If the secretions remain on the skin for too long an odour can occur as the bacteria living on the skin break down the proteins and fatty acids.

All over the body, with the exception of the soles and palms, sebaceous glands lie in the dermis. The function of these glands is to secrete a substance called sebum which acts as a lubricant to prevent the skin and hair from drying out. The sebum consists of a mixture of fats, proteins the debris of dead fat-producing cells and is deposited onto the hair inside the follicles. If there is no hair on a particular surface, the sebum is deposited through ducts.

Homeostasis

Homeostasis involves maintaining a constant internal environment in order for the body to function, regardless of the external conditions. The skin plays an important role in this as it contains heat and cold receptors in the skin which regulates the body temperature, keeping it at around 37°C.

The glands that we have discussed also reduce the growth of fungi by producing acidic secretions, as well as responding to signals from the hypothalamus in the brain. These nerve signals send messages to the glands which stimulates the production of sweat to cool the body down.

The blood vessels within the skin also respond to the hypothalamus and dilate to allow blood to flow closer to the skin and allow heat to be lost, as well as constrict to retain heat within the body when the temperature drops.

The pigmented cells, melanocytes also play a part in homeostasis as they act as a barrier from the damaging effects of ultraviolet light.