Maderson, Paul F. Department of Biology, Brooklyn College, Brooklyn, New York.
Last reviewed:January 2019
Show previous versions
- Growth and replacement
- Evolution and adaptive radiation
- Links to Primary Literature
- Additional Readings
Nonliving, specialized epidermal derivatives characteristic of modern mammals. Hair is a threadlike outgrowth of the epidermis of mammals. However, it is likely that hair was present in at least some therapsid reptiles. Hair consists of keratinized cells, tightly cemented together, which arise from the matrix at the base of a follicle (Fig. 1). A follicle is a tubular epidermal downgrowth that penetrates into the dermis and widens into a bulb (the hair root) at its deep end. The follicle, together with a lateral outgrowth called the sebaceous gland, forms the pilosebaceous system. Rapid cell production in the matrix, as well as differentiation in the regions immediately above, produces a hair shaft, which protrudes from the follicle mouth at the skin surface. See also: Epithelium; Mammalia; Sebaceous gland; Skin; Therapsida
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8500 articles and Research Reviews covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information