Skin Cell Definition

The skin’s fundamental building blocks are skin cells; a big, complicated organ that acts as a shield between our inner organs as well as the external environment. Keratinocytes are the most prevalent kind of skin cell. Its primary function is to provide a dense, impenetrable layer that shields the skin from ultraviolet radiation, harmful chemicals, and pathogenic agents.

However, the skin has extremely specific cells that carepdermisry out vital immunological, photoprotective, and sensory functions. As a consequence, the term “skin cell” refers to any of the four major types of cells found inside the epidermis (or outermost layer) of the skin.

Functions of the Skin

The skin is the body’s largest organ and is important for life. The skin’s principal role is to act as a physical barrier between an organism’s internal environment and the outside world. This guards against harm and infection to interior organs and tissues.

Additionally, by limiting water loss while regulating the body’s temperature, the skin aids in homeostasis. When exposed to sunshine, it shields organisms from the detrimental effects of UV radiation and assists in the creation of vitamin D. Finally, the skin serves as a sense organ, enabling us to detect touch, changes in temperature, and pain.

The epidermis, which is composed of highly specialised cells, ensures that the skin is capable of performing all of these duties (the outermost layer of the skin).

Structure of the Skin

The three basic layers of the skin are the epidermis, dermis, and hypodermis (also known as the subcutaneous layer).

The epidermis is the outermost layer of the skin. This waterproofing shield safeguards the underlying skin layers and other internal tissues against injury, UV damage, toxic chemicals, and other pathogen infections produced by bacteria, viruses, and fungus. The epidermis’s thickness differs depending on its location on the body. The epidermis is only approximately 0.5 mm thick on the delicate skin of the eyelids, but about 1.5 mm thick on the more robust skin of the palms and feet.

The dermis is the thickest of the three layers of skin, located immediately underneath the epidermis. This layer is densely packed with specific structures such as blood arteries, lymph vessels, sweat glands, hair follicles, sebaceous glands, and nerve endings. Additionally, it contains collagen and elastin, both of which are structural proteins that contribute to the skin’s strength and elasticity. The fundamental function of the dermis is to provide oxygen and other nutrients to the epidermis and to aid in temperature control.

The hypodermis (or subcutaneous layer) of the skin is the fatty layer that extends the deepest into the skin. It is mostly made up of fat cells and acts as an insulating layer, aiding in the control of internal body temperature. Additionally, the hypodermis acts as a shock absorber, preventing injury to the internal organs.

What is a Skin Cell?

The term “skin cell” refers to any of the four primary cell types found in the epidermis. Keratinocytes, melanocytes, Langerhans cells, and Merkel cells are all examples of these cells. Each kind of skin cell plays a specific part in the skin’s overall structure and function.

Skin Cells of the Epidermis

Keratinocytes

Keratinocytes comprise the most abundant kind of epidermal skin cell. Approximately 90% to 95% of epidermal cells are keratinocytes.

They synthesise and store keratin, a structural protein that gives skin, hair, and nails their toughness and waterproofing properties. Keratinocytes’ primary job is to produce a robust barrier against infections, UV radiation, and hazardous substances while also limiting water and heat loss from the body.

Keratinocytes are stem cells located in the epidermis’s lowest layer (the basal layer) and are propelled upward through the epidermis’s layers when new cells are generated. As keratinocytes ascend, they diversify and undergo morphological and functional changes.

Mitosis creates keratinocytes in the stratum basal (or basal layer). Basal cells are also used to refer to cells in this layer of the epidermis. As new cells are continuously created, older cells are pushed up into the stratum spinosum, the next layer of the epidermis.

Keratinocytes take on a spiky look in the stratum spinosum (or squamous cell layer) and are referred to as spinous cells or prickle cells. This epidermal layer’s primary job is to preserve the skin’s strength and elasticity.

Following that, the keratinocytes move to the granulosum layer. This layer contains cells that are densely keratinized and have a granular appearance. Keratinocytes flatten and dry out when they approach the skin’s surface.

At the moment keratinocytes reach the stratum lucidum (AKA the translucent layer), they have flattened and died as their length from the nutrient-rich blood supply of the stratum basal increases. The stratum corneum (the epidermis’s outermost layer) is composed of ten to thirty layers of deceased keratinocytes that are excreted from the skin on a regular basis. Corneocytes are another term for keratinocytes of the stratum corneum.

Melanocytes

Melanocytes are a further major kind of skin cell, accounting for between 5% and 10% of the skin cells in the basal layer of the epidermis.

Melanocytes’ principal function is to synthesise melanin, the pigment responsible for the colour of the skin and hair. Melanin is a pigment that protects skin cells from damaging ultraviolet radiation and is created in reaction to sun exposure. When the skin is exposed to the sun for a lengthy period of time, melanin accumulates in it, darkening it, resulting in the formation of a “suntan”.

Langerhans Cells

Langerhans cells are epidermal immune cells that contribute significantly to the skin’s defence against infection. They are found throughout the epidermis, but are most numerous in the stratum spinosum.

Langerhans cells are antigen-presenting cells that engulf and digest pathogens that invade the body. Numerous parts of this complex are exhibited on the top of Langerhans cells and are exposed to naïve T cells in lymph nodes. T cells are activated to generate an innate immune response, while effector T cells are sent to find and destroy the intruding pathogen.

Merkel Cells

Merkel cells are found in the basal layer of the epidermis and are especially numerous on the palms, finger pads, feet, and toe undersides. They are thought to function as touch-sensitive cells due to their proximity to sensory nerve terminals. Merkel cells enable humans to receive sensory information from the outside world (such as touch, pressure, and texture).