Which of the following substances protects the skin from ultraviolet radiation?
Melanin.
Perspiration.
Sebum.
Keratin.
The Correct Answer is A
Melanin is a pigment produced by cells called melanocytes in the skin.
It protects the skin from ultraviolet (UV) radiation by absorbing and dissipating over 99.9% of absorbed UV radiation.
This helps to prevent DNA damage and other adverse effects of UV radiation on the skin.
Choice B. Perspiration is not correct because it is a fluid produced by sweat glands in the skin that helps to regulate body temperature, but it does not protect the skin from UV radiation.
Choice C. Sebum is not correct because it is an oily substance produced by sebaceous glands in the skin that helps to lubricate and protect the skin, but it does not protect the skin from UV radiation.
Choice D. Keratin is not correct because it is a fibrous protein that provides strength and durability to the skin, hair and nails, but it does not protect the skin from UV radiation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
During ovulation, a mature egg is released from the female ovary, enabling it to be fertilized by male sperm cells.
Choice A is incorrect because menstruation is the process of shedding the uterine lining, which occurs when an egg is not fertilized.
Choice B is incorrect because fertilization is the process of a sperm cell joining with an egg cell to form a zygote.
Choice D is incorrect because oogenesis is the process of forming female gametes (eggs) in the ovaries.
Correct Answer is A
Explanation
Cytokines are chemicals released by one type of immune cell to directly activate another type of immune cell.
They are small proteins that act as messengers between cells and play a key role in regulating the immune response.
Choice B. Lysozymes is not the correct answer because lysozymes are enzymes that break down bacterial cell walls and do not directly activate other immune cells.
Choice C. Perforin is not the correct answer because perforin is a protein that forms pores in the membranes of target cells and does not directly activate other immune cells.
Choice D. Granzymes is not the correct answer because granzymes are enzymes that enter target cells and trigger apoptosis (cell death) and do not directly activate other immune cells.
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