| Human Anatomy, 6/e Kent Van De Graaff,
Weber State University
Integumentary System
Chapter SummaryInternal Affairs (203.0K) The Integument as an Organ
- The skin is considered an organ
because it consists of several kinds of tissues.
- The appearance of the skin is
clinically important because it provides clues to certain body conditions
or dysfunctions.
Layers of the Integument
- The stratified squamous epithelium
of the epidermis is composed of five structural and functional layers: the
stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and
stratum corneum.
- Normal skin color is the result
of a combination of melanin and carotene in the epidermis and hemoglobin
in the blood of the dermis and hypodermis.
- Fingerprints on the surface
of the epidermis are congenital patterns, unique to each individual; flexion
creases and flexion lines are acquired.
- The thick dermis of the skin is
composed of fibrous connective tissue interlaced with elastic fibers. The
two layers of the dermis are the papillary layer and the deeper reticular
layer.
- The hypodermis, composed of adipose
and loose connective tissue, binds the dermis to underlying organs.
Functions of the Integument
- Structural features of the skin
protect the body from disease and external injury.
- Keratin and acidic oily secretions
on the surface of the skin protect it from water and microorganisms.
- Cornification of the skin
protects against abrasion.
- Melanin is a barrier to UV
light.
- The skin regulates body fluids
and temperatures.
- Fluid loss is minimal as a
result of keratinization and cornification.
- Temperature regulation is
maintained by radiation, convection, and the antagonistic effects of sweating
and shivering.
- The skin permits the absorption
of UV light, respiratory gases, steroids, fat-soluble vitamins, and certain
toxins and pesticides.
- The integument synthesizes
melanin and keratin, which remain in the skin, and has a role in the synthesis
of vitamin D, which is used elsewhere in the body.
- Sensory reception in the skin
is provided through cutaneous receptors throughout the dermis and hypodermis.
Cutaneous receptors respond to precise sensory stimuli and are more sensitive
in thin skin.
- Certain emotions are reflected
in changes in the skin.
Epidermal Derivatives
- Hair is characteristic of
all mammals, but its distribution, function, density, and texture varies
across mammalian species.
- Each hair consists of
a shaft, root, and bulb. The bulb is the enlarged base of the root
within the hair follicle.
- The three layers of a
hair shaft are the medulla, cortex, and cuticle.
- Lanugo, angora, and definitive
are the three distinct kinds of human hair.
- Hardened, keratinized nails
are found on the distal dorsum of each digit, where they protect the digits;
fingernails aid in grasping and picking up small objects.
- Each nail consists of
a body, free border, and hidden border.
- The hyponychium, eponychium,
and nail fold support the nail on the nail bed.
- Integumentary glands are exocrine,
since they either secrete or excrete substances through ducts.
- Sebaceous glands secrete
sebum onto the shaft of the hair.
- The two types of sudoriferous
(sweat) glands are eccrine and apocrine.
- Mammary glands are specialized
sudoriferous glands that secrete milk during lactation.
- Ceruminous glands secrete
cerumen (earwax).
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