Which of the following functions is performed by the skin to help maintain homeostasis in the human body?

1. Analyze the question The question asks which function of the skin helps maintain homeostasis. Homeostasis means keeping the body's internal environment stable, for example in temperature, water balance and chemical levels.

2. Explain the concept The skin is the largest organ of the body. Its main functions include:

• Protection against germs, injury and UV rays
• Sensation (touch, pain, heat and cold)
• Excretion of small amounts of water, salts and urea through sweat
• Vitamin D synthesis
• Temperature regulation, which is the key homeostatic role

3. Step-by-step solution

When the body is too hot:

• Sweat glands produce sweat, which evaporates and cools the body.
• Blood vessels in the skin dilate (vasodilation), so more heat is lost by radiation.

When the body is too cold:

• Sweating reduces.
• Blood vessels constrict (vasoconstriction), so less heat is lost.
• Erector pili muscles contract, raising hairs to trap an insulating layer of air (goose pimples).
• Shivering generates extra heat.

These responses keep the body at about 37°C, which is a classic example of homeostasis.

Checking the other options:

• B. Filtration of blood: This is done by the kidneys, not the skin.
• C. Production of hormones: This is done by endocrine glands such as the pituitary, thyroid and adrenals. The skin only makes vitamin D, which is not the main hormonal role.
• D. Digestion of food: This is done by the alimentary canal and its associated organs.

4. Answer The correct option is A. Regulation of body temperature.

5. Exam tip Link organs to their homeostatic roles:

• Skin → temperature
• Kidney → water and salt balance, and filtration of blood
• Liver → blood sugar and detoxification
• Pancreas → blood sugar (insulin and glucagon)

When you see "skin" and "homeostasis" together, think of sweat and temperature control. You've got this!