xxx.jpg)
xxx.jpg)
Human Skin and Hair
Not many people have perfectly proportioned faces and bodies, but practically anyone, at any age, can present an attractive appearance if skin is healthy-looking and glowing and hair is clean and shining. Healthy skin and hair can be achieved through good health habits, cleanliness, and personal grooming. Expensive skin-and-hair products may boost self-confidence., but they are a poor substitute for proper diet, exercise, enough sleep, and soap and water or cleansing creams.
The condition of skin and hair reflects a person’s physical and emotional health. Of course, general appearance is determined not only by what is going on inside the body but also by outward circumstances, such as extremes of temperature or the use of harsh soaps. Appearance can also be altered temporarily by cosmetics and permanently by surgery.
The skin is one of the most important organs of the body. It serves as protection against infection by germs and shields delicate underlying tissue against injury. Approximately one-third of the bloodstream flows through the skin, and as the blood vessels contact or relax in response to heat and cold, the skin acts as a thermostat that helps control body temperature. The two million sweat glands in the skin make it a sense organ responsive not only to heat and cold but also to pleasure, pain and pressure.
Certain cells in the skin produce a protective pigmentation that determines its color and guards against overexposure to the ultraviolet rays of the sun. By absorption and elimination, the skin helps regulate the body’s chemical and fluid balance. One of the miracles of the skin is that it constantly renews itself.
The skin is made up of two layers. The outer layer, or epidermis, has a surface of horny, nonliving cells that form the body’s protective envelope. These cells are constantly being shed and replaced by new ones, which are made in the lower or inner layer of the epidermis.
Underneath the epidermis is the dermis, the thicker part of the skin. It contains blood vessels, nerves, and connective tissue. The sweat glands are located in the dermis, and they collect fluid containing water, salt, and waste products from the blood. This fluid is sent through tiny canals that end in pores on the skin’s surface.
The oil or sebaceous glands that secrete the oil that lubricates the surface of the skin and hair are also located in the dermis. They are most often associated with hair follicles.
Hair follicles and oil glands are found over most of the body, with the exception of the palms of the hands and soles of the feet.
The layer of fatty tissue below the dermis called subcutaneous tissue acts as an insulator against heat and cold and as a shock absorber against injury.
