Melanocytes and keratinocytes work together in protecting the skin from UV damage when keratinocytes
accumulate the melanin granules on their superficial portion, forming a UV- blocking pigment layer
provide the melanocyte with nutrients necessary for melanin synthesis
maintain the appropriate pH in order for the melanocyte to synthesize melanin granules
maintain the appropriate temperature so the product of the melanocyte will not denature
The Correct Answer is A
A. accumulate the melanin granules on their superficial portion, forming a UV-blocking pigment layer: Keratinocytes take up melanin granules produced by melanocytes and position them above the nucleus. This arrangement shields nuclear DNA from harmful UV radiation, reducing the risk of mutations and cellular damage.
B. provide the melanocyte with nutrients necessary for melanin synthesis: Nutrients for melanocyte function are delivered through blood supply in the dermis rather than directly by keratinocytes. Keratinocytes do not supply essential substrates for melanin production.
C. maintain the appropriate pH in order for the melanocyte to synthesize melanin granules: pH balance in the skin is regulated mainly by sweat and sebaceous secretions. Keratinocytes do not directly control melanocyte pH for melanin synthesis.
D. maintain the appropriate temperature so the product of the melanocyte will not denature: Temperature regulation is largely a function of dermal blood flow and sweat glands. Keratinocytes do not control melanocyte temperature or prevent denaturation of melanin.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. fibroblasts:Fibroblasts are connective tissue cells responsible for producing extracellular matrix and collagen. They are not part of the epithelium and do not enhance absorptive surface area.
B. thin and permeable:While simple columnar epithelium is relatively thin to allow some absorption, this characteristic alone does not significantly increase surface area for efficient nutrient uptake.
C. dense microvilli:Microvilli are finger-like projections on the apical surface of simple columnar epithelial cells. Their dense arrangement forms the brush border, greatly increasing surface area and enhancing absorption in the small intestine.
D. cilia:Cilia are hair-like structures that move substances across the epithelial surface, such as mucus in the respiratory tract. They do not increase surface area for absorption and are not a feature of absorptive digestive epithelium.
Correct Answer is D
Explanation
A. late prophase:During late prophase, chromosomes condense and the mitotic spindle forms, but cytokinesis has not yet begun as the cell is still preparing for chromosome alignment.
B. early anaphase:Early anaphase involves the separation of sister chromatids toward opposite poles. Cytokinesis does not start at this point because chromosome separation is still in progress.
C. early prophase:Early prophase is the initial stage of mitosis where chromatin condenses into visible chromosomes. Cytokinesis is not initiated at this stage.
D. late anaphase:Cytokinesis begins during late anaphase, when the cell starts forming a cleavage furrow as the chromosomes near the poles. This process continues into telophase, ultimately dividing the cytoplasm into two daughter cells.
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