Structure: Skin and Hair

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.

Pore surrounded by epidermal cells

Sweat from glands in the dermis reaches the skin’s surface through pores such as this one. The large, upright flakes around the pore are dead epidermal cells.

Magnified section of hair

Hair has three layers: the inner medulla (which is usually hollow), a thick pigmented cortex, and an outer cuticle.

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.

Membrane layers

The structure of mucous membranes – rapidly dividing cells in the basal layer below the layer of flat cells – is similar to that of the skin’s epidermis, but lacks a thick, distinctive outer edge.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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