The skin consists of two basic layers: the epidermis, which is the thin outer layer, and the dermis, which is the thick inner layer. The epidermis consists of sheets of tough, flat cells. Hair grows from hair follicles, which are modified regions of epidermis that reach into the dermis. New hair cells, made in the follicle, eventually die to form the scaly hair shaft. The dermis is made of strong, elastic tissue and contains blood vessels, glands, and nerve endings, which respond to stimuli such as heat, pressure, and pain.
Structure: Mucous membranes
Mucous membranes are sheets of cells that protect body areas that must not dry out. These membranes line the mouth and nose; the insides of the eyelids; and the genital, digestive, and respiratory tracts. Special cells in the membranes, called goblet cells, secrete mucus, a sticky protein that lubricates and cleans. At the opening of body cavities, mucous membranes are continuous with the skin.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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