chapter 06 integumentary system copyright © the mcgraw-hill companies, inc. permission required for...
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Chapter 06
Integumentary System
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Introduction A. Organs are body structures composed of
two or more different tissues.
B. The skin and its accessory organs make up the integumentary system.
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Skin and Its Tissues A.The skin is a large organ responsible for:
1. maintaining homeostasis through temperature regulation
2. protection of underlying tissues
3. preventing water loss,
4. housing sensory receptors
5. synthesizing certain chemicals
6. excreting wastes.
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B. The skin consists of an outer epidermis and a dermis, connected to underlying tissue by the subcutaneous layer
(hypodermis).
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Skin of Finger
Epidermis Dermis
EpidermisEpidermis
DermisDermis
Subcutaneous LayerSubcutaneous Layer
Fig06.01a
Epidermis
Dermis
Hair shaft
Sweat gland pore
Sweat
Capillary
Stratum corneum
Stratum basale
Dermal papilla
Arrector pili muscle
Basement membrane
Sebaceous gland
Hair follicle
Sweat gland
Nerve cell process
Adipose tissue
Blood vessels
Muscle
Sweat gland duct
Subcutaneous layer
(a)
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Fig06.01b
Hair follicle
Epidermis
Arrector pili muscle
Sebaceousgland
Dermis
©Image Source/Getty Images
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(b)
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C. Epidermis
1. The epidermis is made up of stratified squamous epithelium and lacks blood vessels.
2. This type of tissue is made up of layers of flattened cells that are
designed to protect underlying layers.3. It makes up the outer layer of skin, and lines the mouth, throat, vagina, and anal canal.
.
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The layer of reproducing cells (the stratum basale), which lies at the base of the epidermis, is well-nourished by dermal blood vessels
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Fig06.02
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Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
Basement membrane
Dermis
Dermal papilla
(a) (b)©The McGraw-Hill Companies, Inc./Al Telser, photographer
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3. Cells are pushed outward as new cells are formed, and
become keratinized as they die. Four or five layers may be seen: stratum basale, stratum spinosum, stratum granulosum, and stratum corneum are always present and the stratum lucidum is found in the thicker palms and soles.
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4. The epidermis is important because it protects against water loss,
mechanical injury, chemicals, and microorganisms.5. Melanocytes, which lie deep in the
epidermis and underlying dermis, produce a pigment called melanin that protects deeper cells from the sun's ultraviolet rays.6. Melanocytes pass melanin to
nearby cells through cytocrine secretion.
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Fig06.03b
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Epidermis
Dermis
(b)
Cellularextensionof melanocyte
Pigmentgranules
Golgiapparatus
Melanocytenucleus
Basementmembrane
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D. Skin Color
1. Skin color results from a combination of genetic,
environmental, and physiological factors.
2. Genetic differences in skin color result from differing
amounts of melanin and in the size of melanin granules.
3. Exposure to sunlight causes darkening of skin as
melanin production increases.
4. Circulation within dermal blood vessels affects skin color.
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E. Dermis
1. The dermis binds the epidermis to underlying tissues. Epidermal ridges and dermal papillae cause the border to be uneven.
2. The dermis consists of connective tissue with collagen and elastic fibers within a gel-like ground substance.
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3. Dermal blood vessels carry nutrients to upper layers
of skin and help to regulate temperature.
4. The dermis also contains nerve fibers, sensory fibers, hair
follicles, sebaceous glands, and sweat glands.
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Accessory Structures of the Skin
A. Nails
1. Nails are protective coverings over the ends of fingers and
toes.
2. Nails consist of a nail plate and stratified squamous epithelial
cells overlying the nail bed, with the lunula as the most actively growing region of the nail root.
3. As new cells are produced, older ones are pushed outward and
become keratinized.
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Fig06.04
Nail bed Nail plateLunulaCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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B. Hair Follicles 1. Hair can be found in nearly all
regions of the skin except palms, soles, lips, nipples, and portions of external genitalia.
2. Each hair develops from cells at the base of a tubelike
depression called the hair follicle. The dermis
contain the hair root.3. As new cells are formed, old cells are
pushed outward and become keratinized, and die
forming the hair shaft.
Fig06.05a
(a)
Hair shaft
Pore
Hair root(keratinizedcells)
Arrector pilimuscle
Sebaceousgland
Basementmembrane
Hair follicle
Region ofcell division
Eccrinesweat gland
Dermalbloodvessels
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Fig06.05b
(b)
Hair follicle
Hair root
Region of celldivision
Adipose tissue
©The McGraw-Hill Companies, Inc./Al Telser, photographer
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4. A bundle of smooth muscle cells, called the arrector pili muscle,
attaches to each hair follicle. These muscles cause goose bumps when cold or frightened.
5. Hair color is determined by genetics; melanin from melanocytes is responsible for most hair colors. Dark hair has eumelanin while blonde and red hair have pheomelanin.
6. The arrector pili muscle attaches to each hair follicle.
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C. Sebaceous glands
1. Sebaceous glands (holocrine glands) are associated
with hair follicles and secrete sebum that waterproofs and moisturizes the hair shafts.
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Fig06.07
Hair follicle
Sebaceous gland
©The McGraw-Hill Companies, Inc./Al Telser, photographer
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D. Sweat Glands 1. Sweat glands (sudoriferous
glands) are either eccrine, which respond to body temperature, or apocrine, which respond to body temperature, stress, and sexual arousal. The secretions exit via a surface pore.2. Modified sweat glands, called ceruminous glands, secrete wax in the ear canal.3. Mammary glands, another
modified type of sweat glands, secrete milk.
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Regulation of Body Temperature
A. Proper temperature regulation is vital to maintaining metabolic reactions.
B. The skin plays a major role in temperature regulation with the hypothalamus controlling it.
C. Active cells, such as those of the heart and skeletal muscle, produce heat.
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D. Heat may be lost to the surroundings from the skin through radiation.
E. The body responds to excessive heat by dilation of dermal blood vessels and
sweating.
F. The body responds to excessive cooling by constricting dermal blood vessels,
inactivating sweat glands, and shivering.
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Healing of WoundsA. Inflammation, in which blood vessels
dilate and become more permeable, causing tissues to become red and swollen, is the body's normal response
to injury.
B. Superficial cuts are filled in by reproducing epithelial cells.
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C. The blood clot and dried tissue fluids form a scab.
D. If the wound is deep, extensive production of collagenous fibers
may form an elevation above the normal epidermal surface forming a scar.
E. Large wounds leave scars and healing may be accompanied by the formation of granulations.
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