Hair is a part of the human body that can be used for decoration or styling. It consists of one or more strands (hairs) that grow from a small, tube-like depression in the skin called the hair follicle and extend into the dermis, where they become a hard, filamentous strand that is referred to as the hair shaft.
A person’s hair can be a very important part of their appearance and may even determine their social status. There are several types of hair and their characteristics can vary significantly from person to person.
Shape and pattern of hair are also different in different cultures. Some people have a natural curl in their hair while others are born with straight hair. The shape of a person’s hair is determined by the cross-sectional shape of the follicle.
Cross-sections of straight hair tend to be round and curly hair is oval or wavy in shape. However, hair that is thick or has a lot of curl can have a variety of cross-sections.
Colouring of hair occurs naturally in the cortex and is based on a mixture of the two pigments melanin and eumelanin. Melanin gives hair brown, black or dark grey shades and pheomelanin provides red or ginger tones.
The amount of pigment in the hair varies from person to person, and also from area to area on the same head. Usually, the darker the color of the hair, the more eumelanin it contains.
There are many factors that influence how a person’s hair grows including genetics, diet, lifestyle, and the condition of the skin. For example, individuals with dry skin are more prone to have coarse hair than those with oily skin.
Types of hair are classified based on their curl patterns, their hair-strand thickness and their overall hair volume. These methods are commonly used to classify hair in hair salons or in the hair care industry.
Hair follicles originate in the scalp and grow through the dermis, which is the outer layer of the skin. Each follicle contains an area of hair-producing cells that mature and fill up with a protein called keratin. The keratin proteins help the hair fibers become tough and flexible.
The keratin proteins can also be changed by external elements, such as sunlight or chemicals in the environment. They can also be damaged by certain diseases and medications.
Protein is the main substance that makes up hair, and it consists of long chains of amino acids. It is also a component of the skin and nails.
Elements that make up the proteins that make up the hair are carbon, oxygen, hydrogen, nitrogen, and sulfur. The five major elements are also found in the cells of the hair follicles and the hair shaft.
The origins of hair are thought to be from the ancestors of mammals, which are believed to have evolved about 300 million years ago. Fossil evidence suggests that the ancestors of the synapsids, a group that is considered to be the first mammals, acquired hair about that time.