Ethnic differences in skin color are primarily caused by differences in the
quantity of melanin produced
quantity of hemoglobin in the blood
UV radiation exposure
number of keratinocytes
number of melanocytes
The Correct Answer is A
A. quantity of melanin produced: Ethnic variations in skin color are due to differences in the amount and type of melanin synthesized and distributed by melanocytes. While all humans have roughly the same number of melanocytes, the activity level of these cells determines pigment intensity.
B. quantity of hemoglobin in the blood: Hemoglobin contributes to skin tone by giving a reddish or pinkish hue, especially in lighter skin. However, it does not account for the baseline differences in ethnic skin color.
C. UV radiation exposure: Sun exposure can increase melanin production temporarily, leading to tanning. However, long-term ethnic differences are genetically determined rather than solely influenced by environmental UV exposure.
D. number of keratinocytes: Keratinocytes are the primary cells of the epidermis and act as recipients of melanin granules from melanocytes. Their number does not vary significantly among ethnic groups and does not explain differences in skin color.
E. number of melanocytes: The number of melanocytes is relatively consistent across all ethnicities. It is the rate of melanin synthesis and the type of melanin produced that create the observed differences in skin pigmentation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. bind the hair root to the dermis:The hair root is anchored to the dermis by the hair follicle itself and connective tissue structures. The receptor does not play a role in binding or physical attachment of the hair root.
B. serve as a source for new epidermal cells for hair growth after the resting stage has passed:New epidermal cells for hair growth arise from the hair matrix at the base of the follicle. The root hair plexus is a sensory nerve ending, not a cell-generating structure.
C. allow the hair to assist in touch sensation:The hair follicle receptor, or root hair plexus, is a network of sensory nerve endings wrapped around the follicle. It detects movement of the hair, making hair an important component of the tactile sensory system.
D. cause apocrine gland secretion into the hair follicle:Apocrine gland secretion is controlled by hormonal and neural signals, but not by the root hair plexus. The plexus functions in sensation, not glandular stimulation.
Correct Answer is A
Explanation
A. bone (osseous) tissue:Bone tissue contains lacunae that house osteocytes, a hard matrix rich in calcium salts for structural support, and is highly vascularized, allowing nutrients and waste to be transported through blood vessels.
B. fibrocartilaginous tissue:Fibrocartilage contains lacunae with chondrocytes but lacks blood vessels and has a less rigid matrix compared to bone, limiting its nutrient supply and healing capacity.
C. cartilage tissue:Cartilage in general contains lacunae with chondrocytes and a flexible matrix, but it is avascular, relying on diffusion for nutrient delivery rather than direct blood supply.
D. areolar tissue:Areolar connective tissue is loose and highly vascular, but it does not have lacunae or calcium-rich matrix. It primarily provides support, cushioning, and elasticity rather than rigid structural support.
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