Health and Beauty
Skin is the largest organ of the human body with a surface area of 1.5-2.0 square meters in an average adult. Skin is 2-3 mm thick, and each 5 square cm of skin may have up to 600 sweat glands, 20 blood vessels, 60,000 melanocytes and over a thousand nerve endings.
The outermost layer of the skin is called epidermis (from Greek "epi" meaning "over"). Among many functions of the skin are protection, sensation, heat regulation, excretion of sweat and water resistance (to keep essential nutrients from washing out of the body).
5 square cm of human skin may contain up to 50 million bacteria, and on oily surfaces the amount of bacteria may reach 400 million per 5 sq. cm. However, these bacteria are so small they all could fit on one pea.
Thirst sensation is the early symptom of dehydration that arises from a lack of fluids and/or increase in the content of certain osmolites such as salt in our body.
In most people dehydration symptoms become noticeable after 2% loss of one’s normal water volume and in addition to thirst may include dry skin, abnormally dark urine, tiredness and headache. 10% to 15% loss of water may result in dim vision, muscle cramps, dizziness. Water losses that exceed 15% are usually fatal.
In adults over age of 50, the thirst sensation diminishes. In a study elderly people were withheld from drinking water for 24 hours, and when in 24 hours water was made available to them, they still did not recognize that they were thirsty.
Teeth are made not of a bone, but of four tissues of different density and hardness: enamel (the hardest substance of human body), dentin, cementum, and dental pulp.
Humans (and mammals in general) are diphyodont, i.e. they develop two sets of teeth during the lifetime: 20 milk teeth and 32 permanent ones. The presence of a higher-than-normal number of teeth is called hyperdontia.
Some animals have more than one set of teeth in their lifetime. For instance, sharks grow a new set of teeth every two weeks. And walrus tusks are canine teeth that never stop growing throughout life.
Caries is one of the most common diseases throughout the world. It is caused by acid-producing bacteria that live off the remains of foods, especially sugars and starches. To prevent tooth decay saliva helps neutralize the acids that increase the pH of the tooth surface.
Jogging is an aerobic exercise, i.e. the one that involves or improves oxygen consumption by the body. In addition to losing weight the other benefits of regular aerobic exercise include toning muscles throughout the body, reducing stress, increasing the total number of red blood cells in the body, facilitating transport of oxygen.
The term jogging in its main modern sense is attested from 1565 but mostly dates from 1948.
In 1966 track coach Bill Bowerman published the book Jogging. He was the one who established jogging programs for men and women of all ages, thus making jogging as an exercise for everyone throughout the United States very popular.
1. On average, scalp has 100,000 hairs. Redheads have the least hairs – 85,000; blondes are the richest with 130,000; brown and black haired people have about 100,000.
2. 90% of scalp hairs are growing and other 10% are resting.
3. Loosing 100 hairs per day from the scalp is normal.
4. Male hair grows faster than female hair.
5. Combing is less damaging than brushing.
Recent comments: