All about Skin, Hair, and Nails

Covering the outside of your body is a protective layer that consists of your skin, hair, and nails. Skin is the body’s largest organ and it has several functions. It waterproofs the body and forms a barrier against bacteria, viruses and the harmful effects of sunlight. Skin also contains sensors that detect pressure, pain, heat and cold enabling you to feel your surroundings. Nails and hair are extension of the skin.

Skin

It consists of two layers: Dermis and Epidermis. The epidermis is the thin, but tough outer protective layer of the skin. It has a number of layers. The inner thicker dermis contains sensory nerve endings, blood vessels, hair follicles and sweat glands.

Pigmentation- Cells in the epidermis make a pigment called melanin, which protects the body against damage by strong sunlight. People with darker skin produce more melanin than those with lighter skin.

Temperature control- Skin helps the body maintain an even temperature of about 37c. if your body gets too hot, glands release sweat and blood vessels widen to give off heat. To cool the body, blood vessels get narrower.

Epidermis- The upper layer of epidermis consists of dead cells packed with a tough protein called keratin, which are constantly being worn and replaced. Cells in the lower epidermis divide and push new cells towards the surface to replace the lost ones. As they move upwards, these cells fill with keratin

Nails

Nails are hard coverings that protect the ends of fingers and toes. Cells in the root of the nail divide constantly, pushing the nail forward over the nail bed. Finger nails grow at a rate of about 5 mm (0.2 inches) each month, but toe nails grow more slowly.

Nail Structure- Nails are made of the tough protein, keratin. The nails are colorless but appear pink because they rest on a bed served by blood vessels. They grow from active skin cells under skin folds at their base and sides. An opaque crescent called the lunula at the base of each nail contains many of these active cells.

Fingerprints- The undersides of your fingers are covered with tiny epidermal ridges that, together with a sticky film of sweat and natural oils, help you to grip objects. When you touch an object, some of the film sticks to the object so that you leave behind a fingerprint.

Hair

Millions of hairs cover your body. There are two types of hair. Fine vellus hair grows over most of the body. Thicker terminal hair grows on the scalp, and makes up the eyebrows and eyelashes. Hairs grow out of pits in the skin called follicles. Hair on your head grow about 1 cm (0.4) inches a month.

Hair Structure- The shaft of a hair consists of three layers. The cuticle forms overlapping scales on the surface of the hair. Below the cuticle, the cortex forms the main part of the shaft and the medulla is the tough core. Cells in the follicle divide and push upwards to form the shaft of the hair.

Types of hair- Whether the hairs on your head are straight, wavy, or curly depends on the shape of the hair follicles they grow from. Round follicles produce straight hair, oval follicles produce curly hair; and curved follicles produce wavy hair.