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💀anatomy and physiology i review

Melanosomes

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Melanosomes are specialized organelles found within melanocytes, the pigment-producing cells located in the basal layer of the epidermis. These organelles are responsible for the production, storage, and transport of melanin, the pigment that determines skin, hair, and eye color.

5 Must Know Facts For Your Next Test

  1. Melanosomes are produced within melanocytes and then transferred to surrounding keratinocytes in the epidermis.
  2. The size, number, and distribution of melanosomes within keratinocytes determine the degree of pigmentation in the skin.
  3. Melanosomes protect the skin from harmful ultraviolet (UV) radiation by absorbing and scattering the energy of UV rays.
  4. Increased melanin production and melanosome transfer are stimulated by UV exposure, leading to skin tanning.
  5. Abnormalities in melanosome structure or function can result in pigmentation disorders such as albinism or vitiligo.

Review Questions

  • Explain the role of melanosomes in skin pigmentation.
    • Melanosomes are the organelles within melanocytes that produce, store, and transport melanin, the pigment responsible for skin, hair, and eye color. The size, number, and distribution of melanosomes within keratinocytes in the epidermis determine the degree of pigmentation in the skin. Increased melanin production and melanosome transfer to keratinocytes is stimulated by UV exposure, leading to skin tanning as a protective mechanism against harmful radiation.
  • Describe how melanosomes contribute to the skin's defense against UV radiation.
    • Melanosomes play a crucial role in protecting the skin from the damaging effects of ultraviolet (UV) radiation. The melanin pigment produced and stored within melanosomes absorbs and scatters the energy of UV rays, preventing the radiation from reaching and potentially damaging the DNA of skin cells. This protective function of melanosomes is enhanced by the increased production and transfer of melanosomes to keratinocytes in response to UV exposure, leading to increased pigmentation and a tanned appearance of the skin.
  • Analyze the potential implications of abnormalities in melanosome structure or function.
    • Disruptions in the normal structure or function of melanosomes can result in various pigmentation disorders. For example, in albinism, a genetic condition characterized by the lack of melanin production, melanosomes are either absent or nonfunctional, leading to the absence of pigmentation in the skin, hair, and eyes. Conversely, in vitiligo, an autoimmune disorder, the immune system attacks and destroys melanocytes, preventing the production and transfer of melanosomes, resulting in the development of white patches on the skin. These types of melanosome abnormalities can have significant implications for an individual's appearance, as well as their susceptibility to skin damage from UV radiation.