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
Osmosis is the movement of water molecules across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.
In a hypertonic solution, the concentration of solutes outside the cell is higher than inside the cell, so water flows out of the cell through aquaporins embedded in the plasma membrane to balance the concentration gradient.
Choice A. Facilitated diffusion is not correct because it is a type of passive transport that involves the movement of molecules across a membrane through specific transport proteins, but it does not specifically refer to the movement of water molecules.
Choice B. Active transport is not correct because it is a type of transport that involves the movement of molecules against their concentration gradient and requires energy in the form of ATP, but osmosis is a passive process that does not require energy.
Choice D. Diffusion is not correct because it refers to the movement of molecules from an area of higher concentration to an area of lower concentration, but it does not specifically refer to the movement of water molecules.
Correct Answer is B
Explanation
The corpus luteum is a structure that develops in the ovary after an egg has been released.
It secretes the hormone progesterone, which prepares the uterus for a fertilized egg to implant and helps maintain the uterine lining during pregnancy.
Choice A. Umbilical cord is not correct because it is a structure that connects the developing fetus to the placenta and provides nutrients and oxygen to the fetus, but does not secrete hormones.
Choice C. Oviduct is not correct because it is a tube that transports eggs from the ovary to the uterus, but does not secrete hormones.
Choice D. Oocyte is not correct because it is an immature egg cell, but does not secrete hormones.
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