Skin Anatomy: Stratum Basale and Melanin

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Questions and Answers

Which of the following best describes the primary function of the stratum basale?

  • To produce melanin and provide a touch-sensitive layer.
  • To rapidly regenerate keratinocytes and provide tactile receptors. (correct)
  • To initiate inflammatory responses and prevent UV radiation absorption.
  • To provide a protective barrier against physical damage to the skin.

What are the primary cells that comprise the stratum basale?

  • Adipocytes, keratinocytes, and mast cells.
  • Stem cells, keratinocytes, and melanocytes. (correct)
  • Keratinocytes, fibroblasts, and melanocytes.
  • Melanocytes, Merkel cells, and Langerhans cells.

What is the mechanism by which melanin protects keratinocytes from UV radiation?

  • Melanin reflects UV radiation away from the cell nuclei.
  • Melanin neutralizes UV radiation through a chemical reaction.
  • Melanin scatters UV radiation, preventing it from damaging DNA.
  • Melanin absorbs UV radiation, preventing it from reaching the cell nuclei. (correct)

How does the distribution of melanin differ between light-skinned and dark-skinned individuals within the epidermis?

<p>In light-skinned people, melanin is digested by lysosomes in the upper layers of the epidermis, while in dark-skinned people it remains throughout the epidermis. (B)</p> Signup and view all the answers

What is the role of Merkel cells, found in the stratum basale?

<p>To act as receptors for touch sensations. (B)</p> Signup and view all the answers

What triggers melanocytes to increase melanin production and transfer it to keratinocytes?

<p>Exposure to ultraviolet radiation. (A)</p> Signup and view all the answers

Besides pigmentation, what other significant function do melanocytes perform in response to UV radiation?

<p>They secrete signaling molecules to modulate immune responses. (B)</p> Signup and view all the answers

Which statement accurately describes the number of melanocytes in different skin tones?

<p>The number of melanocytes is generally the same regardless of skin tone. (B)</p> Signup and view all the answers

Flashcards

Stratum Basale

The deepest layer of the epidermis, responsible for cell division and regeneration.

Stratum Germinativum

Also known as the stratum germinativum, this layer is composed of a single row of stem cells, primarily keratinocytes.

Keratinocytes

These are the most common cells in the stratum basale, responsible for producing keratin, a protein that forms the main component of skin.

Tactile Epithelial Cells (Merkel Cells)

Specialised cells located in the stratum basale, they are responsible for touch sensation.

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Melanocytes

These cells are responsible for producing melanin, the pigment that gives skin its color.

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Melanin

A dark pigment produced by melanocytes, responsible for protecting the skin from UV radiation.

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Suntanning

The process of melanin production, stimulated by ultraviolet (UV) radiation, that results in a tanned appearance.

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Melanocyte Signaling Molecules

Melanocytes also secrete signaling molecules that help regulate the immune response within the skin.

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Study Notes

Stratum Basale

  • Location and Attachment: Deepest epidermal layer, firmly attached to the dermis along a wavy borderline.
  • Structure: Single layer of cells, primarily stem cells known as keratinocytes.
  • Cellular Activity: Rapid cell division; many mitotic nuclei are present.
  • Specialised Cells: Contains tactile epithelial cells (Merkel cells) and melanocytes.
  • Merkel Cells: Sparsely distributed, associated with sensory nerve endings; touch receptors.
  • Melanocytes: Spider-shaped cells, responsible for producing melanin.
  • Melanin Production: Melanin produced in granules, then transferred to keratinocytes via cell processes (spider legs).
  • Melanin's Function: Protects keratinocyte nuclei from UV radiation damage.
  • UV Protection Mechanism: Melanin clusters on the superficial side of keratinocytes, shielding nuclei from UV rays.

Melanin Differences by Skin Tone

  • Distribution in Keratinocytes: In light-skinned individuals the melanin produced by melanocytes is digested by lysosomes in cells above the basal layer. In dark-skinned individuals, melanin remains in keratinocytes throughout the epidermis.
  • Melanocyte Quantities: Dark skin has the same number of melanocytes as light skin. The difference lies in the quantity/granules/concentration of melanin.
  • UV Response: In most skin tones, increased UV radiation causes an increase in melanin production and transfer to keratinocytes resulting in tanning.
  • Additional Roles for Melanocytes: Secrete signaling molecules in response to UV radiation which affect the skin's immune response. These molecules also influence the inflammatory response and likely other regulatory functions.

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