You may have often wondered if the identical twins (i.e. twins coming of the same zygote) have exactly the same fingerprints? The answer is...No!
Their fingerprints are very much alike, as they are genetically identical but NOT exactly THE SAME. Even if patterns in ridges like the arches, whorls, and loops may be alike the ridge count could differ. The friction in each individual blunts to varying extent the ridges. Jutting out of the epidermis is hair. The hair vary in size, thickness, color, density, and distribution over various parts of body. The variation is from race to race, from individual to individual and also according to sex, age, and region of the body of a person.
Human embryo prior to birth is covered with very fine; yellowish silky hair called lanugo. In infancy we have downy vellus hair. Later in adult life the terminal hair replaces these.
We have no hair on the palms, soles, lips, prepuce, glans penis / labia minora and clitoris. Androgens as well as to some extent adrenal and thyroid hormones affect the growth of hair.
If we pull out a hair we see a tiny grain like structure at the base of hair. This is the hair bulb. At the center of the bulb is a dermal papilla. It has a network of capillaries, the minute blood vessels. If no blood flows through the papilla the hair dies. The dermal papilla also contains a nerve only at the basal region and therefore, if a hair is pulled we wince but if it is cut we feel no pain.
Attached to the shaft of hair are obliquely placed arrector pili muscles. These are small bundles of smooth muscles and are involuntary. When these muscles contract the hair stand on their ends and give us the "goose flesh". The goose flesh is a combined effect of the tiny dimples arising due to contraction of the arrector pili and erect hair.
Please take a look at the hair structure in a second at following site - http://www.scf-online.com/english/issue2...
Some animals like bullocks can, at will, move large parts of their skin. They have just below the skin patches of skeletal muscles, called panniculus carnosus. We do not have such muscles.
Hair traps air near the skin to provide invisible, insulating layer. Dense winter coats of many mammals save them from freezing to death. Otters' fur keeps them warm and gives them buoyancy for swimming. . Development of a mane on a male lion and beard development in humans provides indications of sexual maturity. Hair color, distribution and quality are indicators of the general health and vitality of an individual and may be the basis of sexual selection.
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