Epidermis

Epidermis: Types of Cells

• Three main types make up the epidermis:
  1. Keratinocytes
  2. Melanocytes
  3. Langerhans cells

no blood vessels, oxygen and nutrients, urea from diffusion if vascularization happen due to some diseases

thickness is constant anywhere in body

1. Keratinocytes

• Keratinocytes make up the majority of cells (95%).
• Keratinocytes are held together by macromolecular structures that look like stripes (or spines) between cells, called desmosomes (primarily visible in the spinous layer).

2. Melanocytes

• The second type of cell which makes up the epidermis is the melanocyte.

• Melanocytes are staggered along the basal layer at around one in every 10 keratinocytes.

• They are the pigment-producing cells, and transfer their pigment, called melanin, to the keratinocytes in the basal cell layer.

Nevi and Melanoma

• Melanocytic nevi, or moles, are benign collections of melanocytes.
• Melanoma, shown below, is a malignancy of melanocytes.

3. Langerhans Cells

• Langerhans cells are the third type of epidermal cells:
  • They are dendritic cells found in the mid-epidermis.
  • Their main function is in the afferent limb of the immune response by providing for the recognition, processing, and presentation of antigens to sensitized T-lymphocytes, and are important in the induction of delayed-type hypersensitivity.
    • A common skin disease in which Langerhans cells play a prominent role is allergic contact dermatitis, such as poison oak.

Langerhans Cells

Langerhans cells are a type of immune cell found in the skin. They are part of the body’s immune system and play a crucial role in detecting and responding to pathogens, such as bacteria, viruses, and fungi. These cells are named after the Austrian physician Paul Langerhans, who first described them in 1868.

• Antigen presentation: Langerhans cells capture antigens from the skin and present them to T cells, activating the adaptive immune response.
• Immune surveillance: They continuously patrol the skin, monitoring for the presence of foreign invaders.
• Cytokine production: Langerhans cells produce cytokines, which are signaling molecules that help regulate the immune response.