Skin Color and Pigmentation Quiz

Skin Color and Pigmentation

• Melanin contributes to skin color; variations include yellow, reddish-brown, and black hues.
• Produced by melanocytes, melanin levels increase with sunlight exposure, protecting DNA from UV damage.
• Higher melanin content results in darker skin tones, while lower levels lead to lighter skin.
• Carotene, an orange-yellow pigment found in vegetables, can influence skin color, particularly when consumed in large quantities (e.g., carrots).
• Hemoglobin, present in dermal capillaries, imparts a red hue to the skin, influenced by oxygen levels.

Cyanosis

• Cyanosis occurs when hemoglobin is poorly oxygenated, leading to a bluish tint in the skin, particularly noticeable in lips, fingers, and toes.

Other Skin Color Changes

• Erythema (redness) can result from embarrassment, inflammation, hypertension, fever, or allergies.
• Pallor (blanching) may be caused by emotional stress, anemia, low blood pressure, or impaired blood flow.
• Jaundice results in a yellow skin tone due to liver disorders and excess biopigments.
• Bruising (black and blue marks) occurs when blood escapes circulation, potentially indicating conditions like hemophilia or Vitamin D deficiency.

Appendages of the Skin

• Skin appendages, arising from the epidermis, play crucial roles in body homeostasis, including exocrine glands.

Cutaneous Glands

• Sebaceous (oil) glands:

  • Function as holocrine glands, releasing sebum after cells undergo autophagy.
  • Present across the skin, except on palms and soles, providing moisture, softness, and bacterial protection.
  • Can lead to acne when ducts are blocked; blackheads form from dried, oxidized material, while whiteheads remain undried.

• Sweat (sudoriferous) glands:

  • Two types: apocrine and eccrine.

  • Apocrine:

    • Located in armpits and genital areas; produce thick, odorous fluids that begin functioning at puberty.
    • Larger in size compared to eccrine and have minimal impact on temperature regulation.

  • Eccrine:

    • Open onto skin's surface via sweat pores, producing acidic sweat that inhibits bacterial growth.
    • Regulates body temperature through perspiration and contains water, salt, and traces of metabolic waste.

Hair Anatomy

• Hair structure consists of a root enclosed in a follicle and a shaft that projects above the skin.
• Made from hard keratinized epithelial cells with growth occurring in the hair bulb's matrix.
• Melanocytes in the follicle provide pigment for hair color, dependent on the differentiation of nearby cells.
• Hair's density, size, and orientation vary by ethnicity, affecting growth patterns.

Hair Structure

• Central medulla: core made of large cells and air spaces.
• Cortex: thick outer layer of flattened cells surrounding the medulla.
• Cuticle: the outermost layer of overlapping cells, the most heavily keratinized, protecting inner structures and prone to damage at the hair tips.