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C h a p t e r
Structure and
Function of the
Integumentum
Structure and Function of the Skin
Epidermis
Keratinocytes
Melanocytes
Langerhans Cells
Merkel Cells
Dermis
Papillary Dermis
Reticular Dermis
Immune Cells
Blood Vessels
Innervation
Basement Membrane Zone
Appendages of the Skin
Sweat and Sebaceous Glands
Hair and Hair Follicles
Nails
Manifestations of Skin Disorders
Lesions and Rashes
Pigmentary Skin Disorders
Pruritus
Dry Skin
Variations in Dark-Skinned People
T
Integumentary
Function
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U N I T
45
he integumentary system, including the skin and its
appendages (sweat and sebaceous glands, hair folli-
cles, and nails), constitutes a complex organ with many
cell types. The diversity of these cells and their ability to
work together provide many functions needed to cope
with the constantly changing external environment.
Structure and Function
of the Skin
The skin is one of the largest and most versatile organs in
the body. It has a surface area of 1.5 to 2 square meters,
weighs approximately 4 kg (9 pounds), and forms the
major interface between the internal organs and the
external environment. Besides providing a covering for
the entire body surface, the skin performs many other
functions, including protection against physical injury,
sunlight, and microorganisms; prevention of loss of
fluids from the internal environment; regulation of body
temperature; continual reception of sensations from the
environment, such as touch, temperature, and pain; and
synthesis of vitamin D through the action of sunlight on
the skin.
The properties of the skin, such as the thickness of
skin layers, their cell types, the distribution of sweat and
sebaceous glands, and the number and size of hair fol-
licles, vary in different parts of the body. Nevertheless,
certain properties are common to the skin on all areas
of the body. Structurally, the skin consists of two main
