Skin cell

Skin Cell

Skin cells, also known as keratinocytes, are the predominant cell type in the epidermis, the outermost layer of the skin. These cells play a crucial role in the protective barrier function of the skin, as well as in the process of wound healing.

Structure and Function

The skin is composed of three primary layers: the epidermis, dermis, and subcutaneous tissue. The epidermis itself is made up of several layers, with keratinocytes being the most abundant cell type.

Epidermal Layers

1. Stratum Basale: This is the deepest layer of the epidermis where keratinocytes are generated. These cells are mitotically active and give rise to the cells that migrate upwards to form the other layers.

2. Stratum Spinosum: As keratinocytes move up from the stratum basale, they enter the stratum spinosum. Here, they begin to produce keratin, a fibrous protein that provides strength and resilience to the skin.

3. Stratum Granulosum: In this layer, keratinocytes become more flattened and accumulate dense granules of keratin and lipids, which contribute to the waterproof barrier of the skin.

4. Stratum Lucidum: This layer is only present in thick skin, such as that on the palms of the hands and soles of the feet. It provides an additional layer of protection.

5. Stratum Corneum: The outermost layer, composed of dead keratinocytes that have become flattened and filled with keratin. These cells are continuously shed and replaced by new cells from the layers below.

Functions of Keratinocytes

- Barrier Function: Keratinocytes form a physical barrier that protects underlying tissues from pathogens, UV radiation, and physical trauma. - Immune Response: These cells can produce cytokines and other signaling molecules that participate in the skin's immune response. - Vitamin D Synthesis: Keratinocytes play a role in the synthesis of vitamin D when exposed to UVB radiation from sunlight.

Life Cycle of a Skin Cell

The life cycle of a keratinocyte begins in the stratum basale, where it is produced by mitosis. As the cell matures, it migrates upwards through the layers of the epidermis, undergoing a process of differentiation and keratinization. Eventually, the cell reaches the stratum corneum, where it is shed from the surface of the skin.

Clinical Significance

- Skin Cancer: Abnormal proliferation of keratinocytes can lead to skin cancers such as basal cell carcinoma and squamous cell carcinoma. - Psoriasis: This condition is characterized by the rapid turnover of keratinocytes, leading to thickened, scaly patches of skin. - Eczema: A condition where the skin barrier is compromised, often involving inflammation and itching.

Also see

- Melanocyte - Langerhans cell - Dermis - Subcutaneous tissue - Wound healing