What are the primary functions of the skin?

The primary functions of the skin include protecting the body against pathogens and regulating body temperature. The skin acts as a physical barrier, preventing microorganisms and harmful substances from entering the body. Additionally, it has an essential role in the immune response, providing an initial defense against infections.

Regulating temperature is achieved through mechanisms such as sweating and blood vessel dilation or constriction. When the body heats up, sweat glands produce sweat that evaporates from the skin surface, cooling the body down. Conversely, during cold conditions, blood vessels constrict to preserve heat.

In contrast to the chosen answer, other options present functions that are not typically associated with the skin. For instance, facilitating photosynthesis and nutrient absorption pertains more to plants than humans. Skin does not produce blood cells or hormones; this function is mainly carried out by organs like the bone marrow and endocrine glands. Lastly, while the skin contributes to the sense of touch, taste and smell are primarily associated with the tongue and nose, respectively. Thus, protecting against pathogens and regulating temperature are the skin's core functions.