1) With some research, describe how this system:
- controls body temperature,
- protects vulnerable cells from harmful radiation,
- offers protection from pathogens (harmful microbes)
The skin contains sweat glands and blood vessels. When the body temperature rises sweat glands become more active releasing swdeat onto the surface of the skin which evaporates and cools the skin.
Blood vessels also dilate taking more blood close to the surface of the skin where heat can be released from the body.
On cold days when body temperature is low blood vessels in the skin constrict taking less blood to the surface of the skin and preventing heat loss.

The skin contains special cells called melanocytes which contain a pigment known as melanin. This pigment absorbs  UV radiation from the Sun and prevents this harmful radiation travelling deeper into the skin where it can damage the DNA of cells causing them to become cancerous.

The unbroken skin provides a barrier between the internal and external environments and prevents pathogen from gaining entry into the body.

2)  What Vitamin  is produced by the skin? What is the role of this vitamin in the body?
The skin also produces vitamin D. To make vitamin D, your skin needs exposure to the Sun's UV radiation. It is a special kind of UV radiation known as UV-B that is responsible for converting a cholesterol type of substance into a precursor of vitamin D. This precursorn travels in the blood to the liver and kidney where it is synthesised into the form necessary for the body to use.
Vitamin D deficiency concern mainly the health of bones. Vitamin D aids in calcium absorption from the intestine. In the absence or reduction of this vitamin in the body bone is degraded to provide the calcium the body needs.

3) Why is it important for people living in high latitude countries to take vitamin D supplements?
High latitude countries have very little sunlight and so the skin lacks the ability to produce the substance that is used by the body to manufacture vitamin D.