Category Human Body

The colour of a person’s skin depends on his environment. In regions with abundant sunlight, a dark skin colour is necessary to provide protection against the harmful UV rays. Light-skinned people in north Europe, where there is very little sunlight, do not need this protection. UV rays are not always harmful: they are needed for the formation of vitamin D, which the body needs for building bones. The darker the skin, the less sunlight can enter the skin and vitamin D formation is reduced. A dark skin may, therefore, result in Vitamin D deficiency in areas where there is not much sunlight. 

Goose pimples help in regulating the body temperature. When we are exposed to cold temperature or get scared, our body hairs stand up so that the air between them can form an insulating layer. Each hair is permanently anchored to the skin with its root. Small muscles are present at these roots, which contract in case of cold or fear. This is visible on the skin as small bumps. The contraction of the muscles also produces heat in the body. This was an excellent warm-up device for our thickly haired curly ancestors who did not wear clothes. 

In the summers, our skin is often exposed to UV radiation from strong sun that can damage the skin. A pigment, called melanin, is produced in the skin to protect against the harmful radiations from the sun. The more this pigment is produced, the darker, i.e., more tanned, is the skin and the higher is the protection against sunburn. That is why; many light-skinned people get sunburnt very quickly. Sunburn always means damage to the skin. Even when the skin has apparently recovered from the burn, it remains damaged from inside and there is always a high risk of getting skin cancer later. 

Our skin is the largest, heaviest, and the most versatile organ. The skin forms the outer covering of our bodies. The colour of the skin and hair determines our appearance. Without the skin, we would not have any protection against UV rays, injuries, and germs invading from outside. Our sense of touch would not work without it. The skin reacts to the outside stimuli and becomes red, brown, or gets goose pimples. Each person has a unique set of fingerprints, and police can often catch criminals by matching their fingerprints. 

Muscle stiffness is a painful result of overstrained muscles. It frequently occurs on days when the body suffers very strong physical stress. Physical strain causes micro cracks in the muscle fibres, which slowly get filled with water. As a result of this, the tissue gets stretched, which causes pain, and gives rise to inflammation. After a few days of recuperation, the pain usually subsides. 

The muscles are connected with bones through rope-like tendons and can only be contracted. Most of the muscles work in pairs so that different types of movements are possible. Such a muscle pair is needed, for instance, to bend the elbow. While one muscle, the biceps, contracts and bends the arm, the other muscle, the triceps, relaxes. Exactly the reverse happens when the arm is stretched. The signal for muscle contraction or relaxation comes from the brain, which is controlled by us. The musculature of the internal organs works by itself since we cannot control these muscles.