Dermatology Case Studies

Keratinocytes

• The keratinocytes are the cells which make up the five sub-layers of the epidermis as seen in Figure 2
• The outermost layer is the stratum corneum, followed by the stratum lucidum, the stratum granulosum, the stratum spinosum and finally the deepest layer the stratum germinativum or basale
• The stratum basale is the only layer of the epidermis where the cells can multiply
• As new cells are produced in the stratum basale, existing cells change shape and move upwards sequentially forming the upper four layers of the epidermis
• Once close to the surface, these cells lose their nucleus and become full of a firm water-proof protein called keratin
• These keratinocytes, full of keratin, form the stratum corneum which is the protective waterproof outer barrier of the skin (Yousef, 2021)

Melanocytes

• Melanocytes are found in the stratum basale and are cells with long tentacle-like extensions that spread upwards towards the other layers of the skin
• They produce melanin, the dark pigment which protects the skin from UV light
• Sun exposure increases melanin production which causes the skin to tan

Langerhans Cells

• Langerhans cells are cells of the immune system
• Produced in the bone marrow, they migrate to the epidermis where they help activation of the immune system
• Langerhans cells capture antigens (e.g. bacteria) invading the skin, process them and then migrate towards the lymphatic vessels in the dermis
• During this journey, the Langerhans cells mature and become antigen-presenting cells
• Once in the lymph nodes, they can be located in the T cell zones of the lymph nodes where they present antigens to the T cells

Merkel Cells

• The Merkel cells are mechanoreceptors which are found in greatest concentration in the most sensitive areas of the skin such as the lips, fingertips, the oral cavity and hair follicles