The hair follicle is a structure of the skin from which hair grows. The hair follicles grow all over the skin, with the exception of the lips, palms of the hands, and soles of the feet. Hair follicles grow hair by packing old cells together. The hair follicle is supplied with one or more sebaceous glands, which provide sebum, an oily substance that helps lubricate the hair and skin. Apocrine sweat glands also help lubricate the hair follicles of the armpits, groin, and areolae. Areas with thicker hair growth, such as the scalp, have more sebaceous glands. The sebaceous gland, the hair follicle is provided with the arrector pili, a bundle of muscle fibers that creates goose bumps when contracted. Hair follicles also have stem cells at their base, which contribute to regular hair growth. The base of the hair follicle is called the papilla. It consists of connective tissue and a capillary loop, or tiny blood vessel. The papilla is surrounded by the hair matrix, which consists of epithelial cells and melanocytes. The epithelial cells divide very quickly, causing regular hair growth, while the melanocytes provide pigment, and are responsible for hair color.
Review articles are the summary of current state of understanding on a particular research topic. They analyze or discuss research previously published by scientist and academicians rather than reporting novel research results.
Review article comes in the form of systematic reviews and literature reviews and are a form of secondary literature. Systematic reviews determine an objective list of criteria, and find all previously published original research papers that meet the criteria. They then compare the results presented in these papers. Literature reviews, by contrast, provide a summary of what the authors believe are the best and most relevant prior publications.
The concept of "review article" is separate from the concept of peer-reviewed literature. It is possible for a review to be peer-reviewed, and it is possible for a review to be non-peer-reviewed.
Last date updated on June, 2014