Which of the following is not a function of the skin?
a. defense against disease organisms.
b. synthesis of vitamin E.
c. regulation of body temperature.
d. excretion of water and salts.
The Correct Answer and Explanation is:
Correct Answer: b. synthesis of vitamin E
Explanation:
The skin is the largest organ of the human body and serves multiple essential functions that contribute to both protection and overall homeostasis. Let’s break down each of the answer choices to understand why option b is the correct answer.
a. Defense against disease organisms – TRUE
One of the primary functions of the skin is to act as a physical and biological barrier to pathogens. The outermost layer of the skin, the epidermis, contains keratinized cells that form a tough, protective layer. Additionally, the skin has immune cells, such as Langerhans cells, and produces antimicrobial peptides that defend against bacteria, viruses, and fungi. The slightly acidic pH of the skin and the presence of sebaceous secretions also create an unfavorable environment for many harmful organisms.
b. Synthesis of vitamin E – FALSE
This is not a function of the skin. Vitamin E is a fat-soluble antioxidant obtained primarily through the diet, especially from sources like vegetable oils, nuts, and leafy greens. The skin does not synthesize vitamin E. In contrast, the skin does synthesize vitamin D when it is exposed to ultraviolet B (UVB) rays from sunlight. This confusion may arise because both vitamins are essential for skin health, but only vitamin D is synthesized by the skin.
c. Regulation of body temperature – TRUE
The skin plays a vital role in thermoregulation through processes such as sweating and vasodilation or vasoconstriction of blood vessels. When the body is overheated, sweat glands produce sweat, which cools the body as it evaporates. When cold, blood vessels in the skin constrict to retain heat.
d. Excretion of water and salts – TRUE
The sweat glands in the skin help in the excretion of water, salts, and small amounts of urea. This is part of the skin’s excretory function, helping maintain fluid and electrolyte balance.
Summary:
The skin performs many essential functions, but it does not synthesize vitamin E—making option b the correct answer.