Which stratum of the epidermis contains dead keratinocytes

Melanoma develops when melanocytes undergo malignant transformation. Merkel cells, which are tactile cells of neuroectodermal origin , are also located in the basal layer of the epidermis. The squamous cell layer is located above the basal layer, and is also known as the stratum spinosum or "spiny layer" due to the fact that the cells are held together with spiny projections. Within this layer are the basal cells that have been pushed upward, however these maturing cells are now called squamous cells, or keratinocytes.

Keratinocytes produce keratin , a tough, protective protein that makes up the majority of the structure of the skin, hair , and nails.

The squamous cell layer is the thickest layer of the epidermis, and is involved in the transfer of certain substances in and out of the body.

The squamous cell layer also contains cells called Langerhans cells. These cells attach themselves to antigens that invade damaged skin and alert the immune system to their presence. The keratinocytes from the squamous layer are then pushed up through two thin epidermal layers called the stratum granulosum and the stratum lucidum.

As these cells move further towards the surface of the skin, they get bigger and flatter and adhere together, and then eventually become dehydrated and die. This process results in the cells fusing together into layers of tough, durable material, which continue to migrate up to the surface of the skin. The stratum corneum is the outermost layer of the epidermis, and is made up of 10 to 30 thin layers of continually shedding, dead keratinocytes.

The stratum corneum is also known as the "horny layer," because its cells are toughened like an animal's horn. As the outermost cells age and wear down, they are replaced by new layers of strong, long-wearing cells. Darker individuals have a greater concentration of melanin in their skin. Fair-skinned individuals have low melanin levels, and are therefore at higher risk for developing skin cancers.

The epidermis also contains appendages rooted within the dermis, the most notable of which are hair follicles, glands, and nails. Hair follicles are dynamic organs that regulate hair growth. Hair itself is primarily composed of soft keratin, and its main function is to regulate body temperature. The follicle itself also includes a sebaceous gland at the base of the follicle, which secretes sebum an oily, waxy substance that lubricates and waterproofs the hair and skin.

Nails, on the other hand, are composed of hard keratin. The skin is functionally a protective interface between internal organs and the environment, and as a result, it constantly encounters a wide array of toxins, pathogenic organisms, and physical stresses.

To combat these attacks, the skin functions as more than a physical barrier: it is an active immune organ. Stay tuned for more Wound Care Insights - to read more about the skin and its care, check out prior installments in our series, including:. Skin Disease and Long Term Care part one. Skin Disease and Long Term Care part two. Nutrition for Wound Care. Skilled Wound Care is a mobile surgical practice committed to transforming the chronic wound care model in nursing facilities.

There are subtle changes in the skin as a person ages. Loss of proteins and cell turnover causes fluid loss, increased dehydration, and loss of moisture resulting in dry skin. The bacteriostatic ability of the skin decreases with the reduction in sweat glands and sebum, which increases susceptibility for infections. The dermal-epidermal junction of the skin thins and elastin decreases, creating wrinkles.

The number of cutaneous mast cells and Langerhans is reduced, resulting in a decrease in the inflammatory response and impaired wound healing. In summary, as we age, the skin becomes thin and loses its elasticity resulting in wrinkles and delicate, dry skin.

Instant Feedback:. All keratinocytes are derived from Stratum basale cells. Normal aging is associated with a reduction of cutaneous mast cells and Langerhans cells that results in a decreased inflammatory response and impaired wound healing. Bikle, D.