Human Skin Adaptations and Functions Quiz
49 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is a major difference in skin elasticity observed in Caucasian and Latin American subjects?

  • No difference in elasticity based on photo-exposure
  • Elasticity is higher in sun-protected skin
  • Reduced elasticity in photo-exposed sites (correct)
  • Increased elasticity in photo-exposed sites

    • Which statement about fibroblasts in DP skin compared to LP skin is true?

  • They produce less elastin in DP skin
  • They are smaller and less active in DP skin
  • They are absent in LP skin
  • They are larger and more active in DP skin (correct)

    • What significant change occurs to collagen intensity in sun-exposed skin over decades?

  • Collagen intensity significantly decreases from the 1st to the 9th decade (correct)
  • Collagen intensity only decreases in protected skin
  • Collagen intensity remains stable
  • Collagen intensity increases steadily

    • What effect does greater flattening of rete ridges have on skin?

    <p>Leads to greater fragility due to less contact with vascular dermis</p> Signup and view all the answers

    What differentiates the responses of DP and LP skins to solar radiation?

    <p>DP skin shows more uniform aging characteristics</p> Signup and view all the answers

    What is the primary reason for humans' loss of body hair?

    <p>To improve thermoregulation during physical activity</p> Signup and view all the answers

    What are vellus hairs described as in humans?

    <p>Almost invisible and cover most of the surface area</p> Signup and view all the answers

    What evolutionary change coincided with hair loss in humans?

    <p>Development of dark skin pigmentation</p> Signup and view all the answers

    Why is eumelanin-rich pigmentation important for humans?

    <p>It protects against photodegradation of folate</p> Signup and view all the answers

    How has migration affected Vitamin D levels in humans?

    <p>Caused a deficiency of Vitamin D</p> Signup and view all the answers

    What is one consequence of Vitamin D deficiency in children?

    <p>Rickets</p> Signup and view all the answers

    What evolutionary adaptation is associated with increased eccrine sweat glands in humans?

    <p>Better heat loss via evaporation</p> Signup and view all the answers

    Which of the following is NOT a disadvantage of reduced body hair in humans?

    <p>Increased body weight</p> Signup and view all the answers

    What is the optimal pH for the synthesis of related protein 2?

    <p>6.8</p> Signup and view all the answers

    Which skin type is at increased risk for UV-related cancers due to high pheomelanin content?

    <p>Light skin types</p> Signup and view all the answers

    How much more melanin can synthesis be enhanced in certain skin types?

    <p>Up to 10-fold more</p> Signup and view all the answers

    What system was initially used to predict photobiological responses before being extended in 1988?

    <p>Fitzpatrick Skin Phototype Classification</p> Signup and view all the answers

    What are mature melanosomes described as when moving along dendrites to keratinocytes?

    <p>Supra-nuclear caps</p> Signup and view all the answers

    What is the role of melanocytes in relation to keratinocytes?

    <p>Protecting from UV damage</p> Signup and view all the answers

    What does the Individual Typology Angle (ITA) assess?

    <p>Actual pigmentation based on colorimetry</p> Signup and view all the answers

    Which of the following skin types was not included in the original Fitzpatrick classification?

    <p>Type V</p> Signup and view all the answers

    What is the primary focus of the study conducted by Ash et al. (2017)?

    <p>The penetration of light in tissue</p> Signup and view all the answers

    Which publication discusses the clinical and biological characterization of skin pigmentation diversity?

    <p>International Journal of Molecular Sciences</p> Signup and view all the answers

    What key difference does El-Domyati et al. (2002) examine in their study?

    <p>Intrinsic aging versus photoaging</p> Signup and view all the answers

    Which factor is investigated by Goncalves et al. (2023) in relation to skin pigmentation?

    <p>The effect of skin tone modulators and exogenous stress</p> Signup and view all the answers

    What aspect does Jablonski and Chaplin (2017) specifically address in their research?

    <p>Evolution of pigmentation in human lineage</p> Signup and view all the answers

    Which of the following discusses photoprotection strategies for people with skin of color?

    <p>British Journal of Dermatology</p> Signup and view all the answers

    According to Hurbain et al. (2018), what is true about melanosome clusters in keratinocytes?

    <p>They are not degradative organelles</p> Signup and view all the answers

    What is the key factor discussed by Jones et al. (2018) regarding skin pigmentation?

    <p>The vitamin D–folate hypothesis</p> Signup and view all the answers

    What is the primary factor considered as the main determinant of skin aging?

    <p>Photodamage</p> Signup and view all the answers

    Which wavelength of UV radiation is primarily responsible for causing skin cancers?

    <p>UVB</p> Signup and view all the answers

    What happens to the size of sebaceous glands during intrinsic aging in Caucasian skin?

    <p>They increase in size</p> Signup and view all the answers

    Which of the following is NOT a change associated with intrinsic aging of Caucasian skin?

    <p>Increase in collagen levels</p> Signup and view all the answers

    What does melanin do in relation to UV radiation?

    <p>Provides photoprotection</p> Signup and view all the answers

    Which type of UV radiation is primarily filtered out by the ozone layer?

    <p>UVC</p> Signup and view all the answers

    What is a significant effect of chronic UV exposure as illustrated by a truck driver?

    <p>Dermatoheliosis on one side of the face</p> Signup and view all the answers

    Which feature does NOT overlap between intrinsic and extrinsic aging?

    <p>Enlarged sebaceous glands</p> Signup and view all the answers

    Which of the following wavelengths is associated with more profound skin penetration?

    <p>UVA</p> Signup and view all the answers

    What happens to the ratio of collagen type III to type I during intrinsic aging?

    <p>It increases</p> Signup and view all the answers

    What is the primary effect of UV exposure on Thymine bases?

    <p>Covalent bond formation leading to mutations.</p> Signup and view all the answers

    Which type of skin shows a significant increase in melanin after UV exposure?

    <p>Darker pigmented skin.</p> Signup and view all the answers

    What is the effect of visible light (VL) in comparison to UV in terms of pigmentation induction?

    <p>VL is significantly less effective than UV.</p> Signup and view all the answers

    What is a key inflammatory effect of UV radiation?

    <p>Induction of inflammatory cytokines and MMP-1.</p> Signup and view all the answers

    Which of the following statements about infrared light (IR) is correct?

    <p>IR penetrates deeper than visible light.</p> Signup and view all the answers

    What structural change occurs in the skin due to photoaging?

    <p>Disorganized elastin deposition.</p> Signup and view all the answers

    What role does melanin play in relation to solar radiation?

    <p>Melanin is a chromophore that absorbs visible light wavelengths.</p> Signup and view all the answers

    Which group has the highest increase in melanin after UV exposure?

    <p>DP skin.</p> Signup and view all the answers

    What is a consequence of UV radiation on endogenous antioxidants?

    <p>Depletes glutathione and ubiquinone.</p> Signup and view all the answers

    Which skin type exhibits equivalent elasticity in both sun-exposed and sun-protected areas?

    <p>Darker pigmented (DP) skin.</p> Signup and view all the answers

    Study Notes

    Our Skin Tone Rainbow

    • Skin tone variations are a result of evolution.
    • Folate, vitamin D, melanocytes, and melanin are crucial in skin pigmentation.
    • Dark pigmentation (DP) and light pigmentation (LP) are observed.
    • Aging and solar radiation (UV, visible, and infrared) influence skin.
    • Photoaging affects elastin, collagen, and dermal-epidermal junctions.
    • Photoprotection and treatments are available for DP skin.

    Our Family Tree

    • Humans (Homo sapiens) belong to the great apes.
    • Humans evolved approximately 300,000 years ago, with larger brains and lighter skeletons than earlier humans.
    • Fossils and DNA confirm humans are one of over 200 primate species.
    • Humans are categorized within the great ape family, sharing characteristics with chimpanzees, gorillas, and orangutans.
    • Neanderthals are the closest extinct relatives to humans, with Homo heidelbergensis being a common ancestor.

    The Evolution...

    • Humans have less body hair compared to other mammals; they are "functionally naked".
    • Hair loss is believed to be an adaptation improving thermoregulation and heat dissipation during intense physical activity.
    • Vellus hairs cover almost all the body surface.
    • Humans retained body hair in areas such as the head, armpits, and groin.
    • The loss of body hair led to enhanced thermoregulation.
    • Disadvantages include reduced protection from abrasions and UV radiation.

    The Evolution Continued...

    • Accelerated keratinization and epidermal differentiation contributed to skin barrier functions.
    • Genomic evidence links the evolution of permanent, dark eumelanin-rich skin pigmentation with reduced hair and increased eccrine glands.
    • The strongest hypothesis suggests that eumelanin protected folate from photodegradation in the dermal vasculature, which is vital for fertility.
    • Folate deficiencies lead to birth defects and infertility.
    • Folate is important for DNA synthesis, repair, amino acid metabolism, melanin production, and thermoregulation.

    What About Changes to Skin Pigmentation?

    • If human evolution were compressed into a year, the change in skin pigmentation occurred this week.
    • Migration of Homo sapiens occurred approximately 55,000 years ago and led to a vitamin-D deficiency.
    • Vitamin D regulates calcium levels, bone development, and other physiological processes.
    • Reduced UVB levels outside the equatorial regions hinders Vit-D synthesis.
    • Darker pigmentation provides photoprotection.
    • Near the equator, dark pigmentation is a crucial adaptation against photodamage.
    • In regions further away from the equator, lighter pigmentation promotes vitamin-D synthesis.

    Our skin is more than a protective barrier

    • Skin provides a barrier against viruses, bacteria, and other foreign substances.
    • It also prevents dehydration and is one of our five senses (touch).
    • Skin regulates body temperature through sweating and heat retention.

    A reminder of the cells in the epidermis

    • Keratinocytes (95%), Langerhans cells (2%), and Merkel cells (0.5%) are primary components of the epidermis.
    • Melanocytes account for approximately 3% of epidermal cells and have a 1:36 ratio with keratinocytes.
    • This 1:36 ratio is referred to as the epidermal melanin unit.

    Melanocytes & melanin

    • Melanocytes reside in the basal layer of the epidermis.
    • Melanocytes synthesise melanin and transfer it to viable keratinocytes.
    • Pigmentary variations are due to both the number and melanin content of melanosomes (melanin granules) within melanocytes.
    • Melanin consists of eumelanin (brown-black) and pheomelanin (yellow-red).
    • Darker skins have higher eumelanin levels per granule and more melanosomes delivering melanin to keratinocytes.

    Synthesis of melanin

    • Melanin is derived from the amino acid tyrosine.
    • Tyrosinase, tyrosinase-related protein 1, and tyrosinase-related protein 2 are the enzymes in melanin synthesis.
    • Optimal melanin synthesis occurs at pH 6.8.
    • Caucasian skin acidity hinders melanin synthesis, contrasting with darker skin acidity that facilitates it.
    • Mature melanosomes migrate along dendrites and are incorporated into keratinocytes, forming supra-nuclear caps.

    Melanocytes & melanin

    • Melanocytes are involved in protecting keratinocytes by shielding them from UV damage.
    • Eumelanin provides protection, while pheomelanin is potentially phototoxic, increasing risk of UV-related cancers in skin with high pheomelanin.
    • Darker skin types have higher eumelanin levels, more melanosomes, and, thus, greater photoprotection.
    • Higher melanin levels are observed in photo-exposed regions compared to protected areas.

    Skin-typing: Fitzpatrick Skin Phototype Classification

    • Fitzpatrick Skin Phototype Classification (FSPC) was developed in 1975 to determine appropriate UVA doses with psoralen treatments.
    • Initial classification included skin types I-IV and was expanded in 1988 to include V and VI for darker skin tones.
    • Insufficiently describing darker skin tones may lead to inaccuracies in skin classification.

    Skin-typing: Individual Typology Angle (ITA)

    • ITA assesses actual pigmentation based on colorimetry.
    • ITA categorizes skin types from very light to dark based on a calculated angle (e.g., very light >55 degrees).
    • Higher angles correlate with lighter skin, while lower angles correspond to darker skin.
    • More objective method compared to Fitzpatrick scale.

    Pigmentation and Photoprotection

    • DNA damage from sun exposure is reduced in dark skin compared to light skin, by about a factor of three.
    • Studies found higher rates of skin cancer in lighter-skinned individuals compared to darker-skinned individuals (e.g., Caucasian vs. African-American).
    • Darker skin provides superior protection against solar radiation.
    • Highly pigmented skin offers significantly higher photoprotection.

    Non-pigmentary differences in DP and LP skin

    • Differences exist in the dermal-epidermal junction, rete ridges (DP skin has more regular and pronounced ridges), and dermal protein composition.
    • Monocyte chemotactic protein-1 (MCP-1) levels are higher in darkly pigmented skin, relevant to wound healing.
    • Post-inflammatory hyperpigmentation (PIH) is more common in darkly pigmented skin, but is not the sole indicator of aging.

    Aging - General

    • Intrinsic aging reflects the natural effects of time on skin, noticeable even in areas shielded from the sun.
    • Extrinsic aging is caused by environmental factors; for example, UV, visible light, and infrared light, causing premature skin aging most pronounced on the exposed parts of the body, including the face, neck, and hands.
    • Chronic sun exposure greatly impacts aging, evident in one-sided darker-shaded facial skin due to prolonged sun exposure.

    Aging - Intrinsic Caucasian Skin

    • Intrinsic skin aging in Caucasians is tied to decreases in melanocytes and Langerhans cells, potentially leading to increased skin cancer risk.
    • Darker skin types also exhibit reduced melanocytes but increased melanophages. This leads to less even skin pigmentation.
    • Sebaceous gland size increases in Caucasians.
    • Although sebaceous gland size in Caucasians increases, total sebum secretion reduces.
    • MMP (matrix metalloproteinases) levels rise, as do degradation levels, and collagen type III/I ratios.

    Solar radiation: UV

    • UV radiation (UVA, UVB, UVC) is a critical aging factor.
    • UVC is filtered by the ozone layer.
    • UVB primarily affects the epidermis and upper dermis, while UVA penetrates deeper.
    • Longer wavelengths have deeper penetration and higher energy.
    • Shorter wavelengths have higher energy and greater penetrating ability.
    • UVB, especially, is associated with tanning and skin cancer.
    • UVA causes indirect DNA damage as part of aging.

    Solar radiation: UV

    • UVB is significantly more erythemogenic than UVA.
    • Melanin effectively absorbs UV energy and dissipates it as heat.
    • Without melanin, DNA, particularly thymine bases, could be damaged.
    • UV exposure increases melanin in DP skin more than in LP skin, although the increments differ between skin tones.
    • UV induces ROS and depletes endogenous antioxidants like glutathione, tocopherol, and ubiquinone.
    • UV also leads to collagen degradation and inhibits collagen formation.

    Solar radiation: visible light (VL)

    • Visible light (VL), at 400-760nm, penetrates deeper into the skin compared to UV radiation.
    • Melanin absorbs all visible light wavelengths, causing increased body temperature and a redness response.
    • The vasodilation response to VL is more prominent in darker skin due to higher melanin concentrations.
    • VL contributes to skin pigmentation, though less effective compared to UV in inducing pigmentation.
    • VL can trigger reactive oxygen species and inflammation, especially in comparison to UV.

    Solar radiation: infrared light (IR)

    • Infrared radiation (760 nm-1 mm) penetrates deep into the skin.
    • IRA, IRB, and IRC penetrate the epidermis, dermis, and subcutaneous tissue.
    • Infrared radiation causes thermal effects, like vasodilation, leading to warmth and erythema.
    • Unlike UV, any resulting pigmentation from IR is indirectly mediated through thermal effects.

    Photoaging - Elastin

    • Exposure to sunlight can cause elastosis.
    • The accumulated elastin in the upper dermis of sun-exposed skin is morphologically abnormal, potentially occupying areas of lost collagen.
    • Fibrillin-rich microfibrils involved in elastin deposition are susceptible to UV radiation.
    • Darker skin effectively resists UV radiation's impact on elasticity.

    Photoaging - Collagen

    • Collagen type I and III levels decrease with sun damage.
    • Collagen production decline with aging, more noticeably in sun-exposed skin.
    • Sun exposure causes significant collagen reductions in the 1st to 9th decades.
    • Sun-damaged skin shows roughly a 40% reduction in type III pro-collagen compared to non-damaged skin.

    Photoaging - Dermal-Epidermal Junction

    • The flattening of the dermal-epidermal junction (rete ridges) increases with photoaging, especially in skin exposed to the sun.
    • Less contact between the vascular dermis and epidermis reduces nutrient supply, impacting skin health and increasing fragility.
    • Increased regularity and prominence of rete ridges in DP skin can partly mask the impacts of aging compared to the epidermal thinning associated with LP skin.

    Photoaging

    • DP and LP skin exhibit different responses to solar radiation.
    • LP skin exhibits effects predominantly from extrinsic aging (effects of sun exposure).
    • DP skin shows delayed intrinsic aging effects.
    • DP skin has a greater predisposition to dyschromias and more susceptibility to irregularities in pigmentation relating to aging.
    • While LP skin shows faster extrinsic aging, DP skin may show this effect later by 20 years (or more).

    Photoaging LP skin

    • Two main extrinsic aging phenotypes are observed:
    • HP (hypertrophic) is characterized by deep wrinkles, skin laxity, and impaired wound healing. This is common in LP skin.
    • AP (atrophic) is characterized by smooth skin, fine wrinkles, frequent spider veins, depigmentation, and actinic keratosis. This is common in LP skin.

    Photoprotection for DP skin

    • The misconception that darker skin is resistant to skin cancer is inaccurate.
    • Photoprotection methods can mitigate effects like dyspigmentation in darker skin from VL, or infrared radiation.
    • Physical sunscreens are preferable to prevent negative effects of thermal absorption on VL exposure.
    • Antioxidants help combat damaging free radicals (ROS).

    Treatments for DP skin

    • Treatments for uneven skin pigmentation in darkly pigmented skin include hydroquinone, azelaic acid, and kojic acid.
    • Tretinoin can be used, however, hyperpigmentation can result from contact dermatitis.
    • The potential benefits of these treatments include reductions in melanin, leading to more even skin tone. Improvement in fine wrinkles and collagen stimulation.

    Conclusion

    • DP and LP skin exhibit differences in their responses to factors like solar radiation, resulting in varied patterns of aging.
    • DP skin features more pronounced rete ridges, promoting nutrient delivery.
    • DP skin's prominent melanin content effectively protects against photoaging and skin cancer.
    • DP skin may benefit from physical sunscreens due to its susceptibility to thermal effects of radiation (VL and IR).
    • LP skin is more susceptible to extrinsic aging with two main phenotypes (HP and AP). This makes it important to use photoprotection.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Our Skin Tone Rainbow PDF

    Description

    This quiz explores various aspects of human skin, including differences in elasticity among ethnic groups, the impact of sun exposure on collagen, and the evolutionary implications of hair loss. Test your knowledge on skin responses to environmental factors and physiological changes that have occurred in humans over time.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser