Functions of hair

Human scalp hair provides both protective and cosmetic or adornment functions. Scalp hair protects the head from the elements by functioning as a thermal insulator. Hair also protects the scalp against sunburn, other effects of light radiation, and mechanical abrasion. 

Hair on parts of the body other than the scalp provides related protective and adornment functions. The adornment function of eyebrows is to the beholder. However, eyebrows also inhibit sweat and prevent extraneous matter from running into the eyes. In addition, eyebrows protect the bony ridges above the eyes and assist in communication and in the expression of emotion. 

Eyelashes are also important to adornment. Eyelashes protect the eyes from sunlight and foreign objects, and they assist in communication. Nasal hairs filter inspired air and retard the flow of air into the respiratory system, thus allowing air to be warmed or cooled as it enters the body. Hair on other parts of the anatomy serves related functions. In addition, a general function of all hairs is as sensory receptors because all hairs are supplied with sensory nerve endings. The sensory receptor function can enhance hair in its protective actions. 

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Blood cannot provide the chronometric function of hair. Consequently, any attempt at monitoring compliance requires frequent blood sampling. And even then the results cannot match the accuracy of hair analysis, since a doubling of the dose does not result in the same accurate relative changes in blood drug levels as in the case of hair. The lower accuracy results from interfering "peak" and "trough" kinetic effects of blood analysis and from the fact that even pseudo-steady-state kinetic conditions in blood cannot approach the accuracy of the dosimetric function of hair. The situation with urinalysis is even less certain. 

C Someone suggests that one function of hair is to insulate Ihe head. Do you agree with this suggestion ... 

Three distinct regions containing different types of cells are generally apparent in cross sections of human hair fibers (see Figures 1-3 and 1-7). Tliese three cellular regions and the intercellular matter are described in summary form in the introductory section. After brief discussions of the functions of hair, hair growth/hair loss, and treatments for hair loss, the remainder of this chapter focuses on these three types of cells and the intercellular binding material of human scalp hair. 

Fig. 3 Ratio of the transmission of light in skin depth as a function of hair color on the skin...

There are functionally different types of hair straightening preparations, ie, those which produce temporary straightening and those which are designed to accomplish permanent effects. 

Fig. 1. Schematic of the cross section of a mammal s skin. The relative size and function of the parts depend on the species and breed of the animal. For goats, where the wool or hair is sparse because it is not needed for warmth, the skin is dense to provide protection for sheep protected primarily by heavy wool, the skin contains more oil (sebaceous) glands to lubricate the wool for catde, both the hair and the heavy hide stmcture protect the animal (3).

The natural polymers known as proteins make up about 15% by mass of our bodies. They serve many functions. Fibrous proteins are the main components of hair, muscle, and skin. Other proteins found in body fluids transport oxygen, fats, and other substances needed for metabolism. Still others, such as insulin and vasopressin, are hormones. Enzymes, which catalyze reactions in the body, are chiefly protein. 

Some sprays include vitamins such as tocopherols (vitamin E) or panthenol, which is metabolized in the skin to become pantothenic acid, a B vitamin. Since hair does not metabolize ( It s dead, Jim ), these sprays perform the functions of antioxidants (tocopherols). In other words, they add shine and moisture (panthenol) rather than perform their normal vitamin roles. Moisture helps prevent damage during combing. 

Multiunit smooth muscle is located in the large blood vessels, eyes (iris and ciliary muscle of the lens), and piloerector muscles at the base of hair follicles. This type of muscle consists of discrete smooth muscle cells or units that function independently. Each of these units is innervated by the... 

As the central function of a shampoo is to cleanse the hair, the primary ingredient of a shampoo is a detergent (also known as a surfactant). Many shampoos, particularly those targeted for babies and children, claim to cause no eye irritation or sting. A no-tears formulation achieves this claim by carefully adjusting the nature of the surfactants. In particular, the identity and concentration of surfactants with an ionic or charged portion are controlled to minimize both eye and skin irritation. 

The identified genes code for a variety of proteins, including transcription factors that are important for inner-ear development, cytoskeleton proteins that are responsible for the specialized architecture of hair cells, extracellular matrix molecules that make up some of the specialized acellular structures of the inner ear, and still others whose function is not yet clear. 

The surprise is that genes clearly involved in mechano-transduction have not yet been identified by the deafness-gene approach. Clearly disruption of hair-cell function at many levels can lead to deafness, so it is expected that deafness genes include those involved in inner-ear development, in ion balance in the endolymph, and in structural integrity of hair cells. Examination of deafness genes in zebrafish has been particularly thorough, however, and... 

The balance between excess and insufficient zinc is important. Zinc deficiency occurs in many species of plants and animals, with severe adverse effects on all stages of growth, development, reproduction, and survival. In humans, zinc deficiency is associated with delayed sexual maturation in adolescent males poor growth in children impaired growth of hair, skin, and bones disrupted Vitamin A metabolism and abnormal taste acuity, hormone metabolism, and immune function. Severe zinc deficiency effects in mammals are usually prevented by diets containing >30 mg Zn/kg DW ration. Zinc deficiency effects are reported in aquatic organisms at nominal concentrations between 0.65 and 6.5 pg Zn/L of medium, and in piscine diets at <15 mg Zn/kg FW ration. Avian diets should contain >25 mg Zn/kg DW ration for prevention of zinc deficiency effects, and <178 mg Zn/kg DW for prevention of marginal sublethal effects. 

Testosterone is the most important of the male sexual steroids (androgens), it is synthesized in the Leydig intersitial cells of the testes, and controls the development and functioning of the male gonads, it also determines secondary sexual characteristics in men (muscles, hair, etc.). 

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