Difference Between Keratinocytes and Melanocytes

Main Difference – Keratinocytes vs Melanocytes

Epidermis and dermis are the two layers of the skin of animals. Keratinocytes and melanocytes are two types of cells found in the epidermis. Both keratinocytes and melanocytes are anatomically related by forming the “epidermal-melanin unit”. The interaction between keratinocytes and melanocytes is responsible for the synthesis, transfer, transport, and the deposition of melanosomes in the skin. This complete process is known as melanin production. Melanin is the pigment that gives color to the skin, protecting it from ultraviolet radiation. The main difference between keratinocytes and melanocytes is that keratinocytes form a barrier to the mechanical damage of the skin whereas melanocytes protect the skin from UV by producing melanin.

Key Areas Covered

1. What are Keratinocytes
     – Definition, Structure, Role
2. What are Melanocytes
     – Definition, Structure, Role
3. What are the Similarities Between Keratinocytes and Melanocytes
     – Outline of Common Features
4. What is the Difference Between Keratinocytes and Melanocytes
     – Comparison of Key Differences

Key Terms: Basal Layer, Epidermis, Keratin, Keratinocytes, Melanin, Melanocytes, Skin Color

What are Keratinocytes

Keratinocytes are the epidermal cells that produce keratin. The epidermis is made up of stratified epithelium. Keratinocytes are found in the deep basal layer of the stratified epithelium of the epidermis. Therefore, these cells are sometimes called the basal cells or basal keratinocytes. Typically, 95% of the cells in the epidermis are keratinocytes. Some squamous keratinocytes are found in the mucosa of the esophagus, mouth, corneal, conjunctival, and genital epithelia. The main function of keratinocytes is to produce keratin. In addition to the production of keratin, keratinocytes produce tight junctions with nerve endings of the skin. Furthermore, keratinocytes keep both Langerhans cells and lymphocytes in place. Keratinocytes in the skin of a mouse are shown in figure 1.

Figure 1: Keratinocytes (green)

Keratin is the major protein found in the keratinocytes, forming the cytoskeleton of the cell. It serves as a physical barrier between the organism and the external environment, preventing the entrance of pathogens and toxins. It also prevents the loss of moisture and heat from the body. Keratin also forms hair and nails. Keratinocytes serve as immunomodulators, secreting inhibitory cytokines.

What are Melanocytes

Melanocytes are the mature melanin-forming cells in the skin. Both mammals and birds have melanocytes. Melanocytes migrate to the epidermis from the neural crest during embryonic development. Melanocytes are dendritic cells. The main function of melanocytes is to produce melanin. Melanocytes and melanin in the skin are shown in figure 2.

Figure 2: Melanocytes and Melanin

The two types of melanin produced by melanocytes are dark brown eumelanin and yellowish or pale red phaeomealnin. Both melanin types are formed by the oxidation of tyrosine by the enzyme tyrosinase. The production of melanin is regulated by a melanocyte-stimulating hormone. The dendrites of the melanocytes are responsible for the transfer of melanin to the adjacent epidermal cells such as keratinocytes. This structure is referred to the ‘epidermal-melanocyte unit’.

Similarities Between Keratinocytes and Melanocytes

• Keratinocytes and melanocytes are two types of cells in the epidermis of animals.
• Both keratinocytes and melanocytes protect the skin.
• Both keratinocytes and melanocytes function together to form the epidermal-melanin unit.

Difference Between Keratinocytes and Melanocytes

Definition

Keratinocytes: Keratinocytes refer to the epidermal cells that produce keratin.

Melanocytes: Melanocytes refer to the mature melanin-forming cells in the skin.

Differentiation

Keratinocytes: Keratinocytes are differentiated from the basal layer of the epithelium.

Melanocytes: Melanocytes are differentiated from the neural crest cells.

Production

Keratinocytes: Keratinocytes are responsible for the production of keratin.

Melanocytes: Melanocytes are responsible for the production of melanin.

Number of Cells in the Epidermis

Keratinocytes: Most epidermal cells are keratinocytes.

Melanocytes: The number of melanocytes in the skin is less than the number of keratinocytes.

Role

Keratinocytes: Keratinocytes serve as a physical barrier between organisms and the external environment. They also form hair and nails.

Melanocytes: Melanocytes are responsible for the color of the skin.

Conclusion

Keratinocytes and melanocytes are two types of epidermal cells found in the skin. Keratinocytes are the most abundant cells in the epidermis. They are responsible for the production of keratin that serves as the mechanical barrier for damage. Melanocytes are responsible for the production of melanin that provides the color to the skin. This is the main difference between keratinocytes and melanocytes.

Reference:

1. “Structure, Function, Immunity and Differentiation.” Keratinocytes, Available here.
2. “Melanocyte.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 29 June 2017, Available here.

Image Courtesy:

1. “Proliferative response induced by a tumor promoter in the epidermis of a wild-type mouse – image.pbio.v11.i07.g001” By M. Menacho-Márquez – PLOS Biology Issue Image | Vol. 11(7) July 2013 (CC BY 2.5) via Commons Wikimedia
2. “Illu skin02” (Public Domain) via Commons Wikimedia