It requires about 10 days after initial sun exposure for melanin synthesis to peak, which is why pale-skinned individuals tend to suffer sunburns of the epidermis initially. Thus, the amount of melanin present in our skin is dependent on a balance between available sunlight and folic acid destruction, and protection from UV radiation and vitamin D production. In contrast, too much melanin can interfere with the production of vitamin D, an important nutrient involved in calcium absorption. This increased melanin accumulation protects the DNA of epidermal cells from UV ray damage and the breakdown of folic acid, a nutrient necessary for our health and well-being. The accumulation of melanin in keratinocytes results in the darkening of the skin, or a tan. Exposure to the UV rays of the sun or a tanning salon causes melanin to be manufactured and built up in keratinocytes, as sun exposure stimulates keratinocytes to secrete chemicals that stimulate melanocytes. Dark-skinned individuals produce more melanin than those with pale skin. Eumelanin exists as black and brown, whereas pheomelanin provides a red color. The relative coloration of the skin depends of the amount of melanin produced by melanocytes in the stratum basale and taken up by keratinocytes. Changes in lifestyle, specifically in diet and exercise, are the best ways to control body fat accumulation, especially when it reaches levels that increase the risk of heart disease and diabetes. Not only is this a problem for the individuals affected, but it also has a severe impact on our healthcare system. Recent studies indicate that a distressing percentage of our population is overweight and/or clinically obese. Although periodic accumulation of excess fat may have provided an evolutionary advantage to our ancestors, who experienced unpredictable bouts of famine, it is now becoming chronic and considered a major health threat. In much of the developed world, insufficient exercise coupled with the ready availability and consumption of high-calorie foods have resulted in unwanted accumulations of adipose tissue in many people. In many animals, there is a pattern of storing excess calories as fat to be used in times when food is not readily available. Therefore, its accuracy as a health indicator can be called into question in individuals who are extremely physically fit. The body mass index (BMI) is often used as a measure of fat, although this measure is, in fact, derived from a mathematical formula that compares body weight (mass) to height. Men tend to accumulate fat in different areas (neck, arms, lower back, and abdomen) than do women (breasts, hips, thighs, and buttocks). Fat distribution changes as our bodies mature and age. ![]() Where the fat is deposited and accumulates within the hypodermis depends on hormones (testosterone, estrogen, insulin, glucagon, leptin, and others), as well as genetic factors. This stored fat can serve as an energy reserve, insulate the body to prevent heat loss, and act as a cushion to protect underlying structures from trauma. Adipose tissue present in the hypodermis consists of fat-storing cells called adipocytes. The hypodermis is home to most of the fat that concerns people when they are trying to keep their weight under control. Fingerprints are unique to each individual and are used for forensic analyses because the patterns do not change with the growth and aging processes. In a growing fetus, fingerprints form where the cells of the stratum basale meet the papillae of the underlying dermal layer (papillary layer), resulting in the formation of the ridges on your fingers that you recognize as fingerprints. Melanin gives hair and skin its color, and also helps protect the living cells of the epidermis from ultraviolet (UV) radiation damage. ![]() The second is a melanocyte, a cell that produces the pigment melanin. These cells are especially abundant on the surfaces of the hands and feet. The first is a Merkel cell, which functions as a receptor and is responsible for stimulating sensory nerves that the brain perceives as touch. Two other cell types are found dispersed among the basal cells in the stratum basale. As new cells are formed, the existing cells are pushed superficially away from the stratum basale. ![]() All of the keratinocytes are produced from this single layer of cells, which are constantly going through mitosis to produce new cells. A basal cell is a cuboidal-shaped stem cell that is a precursor of the keratinocytes of the epidermis. The stratum basale is a single layer of cells primarily made of basal cells. ![]() \right)^2 ( ∂ x ∂ z ) 2 + ( ∂ y ∂ z ) 2 = ( ∂ r ∂ z ) 2 + r 2 1 ( ∂ θ ∂ z ) 2.The epidermis of thick skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. Recall that Cartesian and polar coordinates are related through the transformation equations
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |