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Chapter 5:

The Integumentary System
An Introduction to the Integumentary System
The integumentary system makes up about 16% of total body weight
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5-2 m² (16
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5 sq ft) in
area
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It has 2 major parts the cutaneous membrane or skin, and the accessory
structures
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The cutaneous layer has 2 components: the epidermis or superficial epithelium, and the
dermis, an underlying layer of connective tissues
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The accessory structures include hair, exocrine glands, and nails
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Hypodermis) (also known as the superficial fascia or subcutaneous layer) is loose connective
tissue deep to the dermis
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The general functions of the integumentary system:
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Protection of underlying tissues and organs
Excretion of salts, water, and organic waste by glands
Maintenance of body temp (insulation and evaporation)
Production of melanin (protection against UV)
Production of keratin (protection against abrasion; water repellent)
Synthesis of vitamin D3 (a steroid/hormone important to calcium metabolism)
Storage of lipids
Detection (general senses)
Coordination (immune response)

5-1
The epidermis is composed of layers with various functions
The epidermis is avascular because there are no local blood vessels, epidermal cells rely on the diffusion
of nutrients and oxygen from capillaries within the dermis
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These cells form
several layers of strata, and contain large amount of the protein keratin
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It has 4 layers of keratinocytes
Thick skin) is found on the palms of the hands and the soles of the feet
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The order of the layers from top to bottom is:
I
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The Stratum lucidum
III
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The Stratum spinosum
V
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The stratum basale forms Epideral ridges- (fingerprints)
and which extend into the dermis and are adjacent to dermal projections called dermal papillae that
project into the epidermis
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They are stem cells that divide to
replace superficial keratinocytes

Tactile disc) specialized epithelial tactile cells that has merkel cells with sensory nerve terminals
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Stratum Spinosum
Each time a stem cell divides, 1 of the daughter cells is pushed to the Stratum spinosum
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Dendric cells) also known as Langerhan cells, cells that participate in the immune response
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It consists of 3-5 layers of
keratinocytes
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It is the basic structural component of hair and
nails
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Stratum corneum
is at the exposed surface of both thick and thin skin
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Is the formation of protective, superficial layers of cells filled
with keratin
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Blisters) fluid accumulation in pockets
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Xerosis) excessively dry skin
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Chapter 5:

5-2
Factors influencing skin color are pigmentation and dermal
circulation
The most distinguishing characteristic of humans is skin color
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Carotene) is an orange-yellow pigment that normally accumulates in epidermal cells
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Melanin) is a pigment produced by melanocytes, pigment producing cells
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The ratio of melanocytes to basal cells ranges between 1:4 and 1:20, depending on the region
of the body
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The Role of Dermal Circulation
Blood contains red blood cells filled with the pigment hemoglobin, which transports oxygen
in the blood stream
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Cyanosis) bluing of the skin due to a decline of oxygen
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Illnesses and skin color:
Jaundice
• buildup of bile produced by liver
• yellow color (pigment accumulates in body fluids)
Pituitary Tumor
• excess MSH (melanocyte-stimulating hormone)
• skin darkening
Addison's Disease
• a disease of the pituitary gland
• excess ACTH (adrenocorticotropic hormone)
• skin darkening
Vitiligo
• loss of melanocytes & color (1% of population)
• possibly related to immune dysfunction (e
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thyroid gland disorders)

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Chapter 5:

5-3
Sunlight causes epidermal cells to convert a steroid into vitamin D3
Cholecalciferol) or vitamin D3 is a cholesterol-related steroid broken down by beneficial sun
exposer
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Inadequate supply leads to impaired
bone maintenance and growth
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Rickets) lack of vitamin D3

5-4
Epidermal Growth factor has several effects on the epidermis
and epithelia
Epidermal growth factor) is 1 of the peptide growth factors
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It has 2 major components the
papillary layer and reticular layer
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Containing capillaries, lymphatic vessels, and sensory
neurons that supply the surface of the skin
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It consists of dense irregular connective tissue
containing both collagen and elastic fibers
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Collagen = it being strong,
and Elastic fibers = stretchability
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Stretch marks) damage to the dermis that prevents recoiling back to its original position
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Cleavage Lines
Cleavage lines) also called tension lines or langer lines
Parallel cuts- remain shut, heals well (less scaring)
Right angle cuts- pulls open (results in more scaring)

Innervation of the Skin
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Nerve fibers in the skin control:
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blood flow
gland secretion rates
monitor sensory receptors in dermis and deep layers of epidermis
• light touch—located in dermal papillae
• deep pressure and vibration---located in the reticular layer
• temp and pain--- located in the epidermis

The hypodermis connects the dermis to underlying tissues
Hypodermis) or subcutaneous layer lies deep in the dermis
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Subcutaneous fat makes up about 80% of all body fat
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The are produced by hair follicles
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Arrector pili) a muscle formed by a bundle of smooth muscle cells
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Chapter 5:

Hair Production
Hair bulb) where hair production begins
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Hair matrix) layer of epithelia cells in contact with the hair papilla
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Cortex) an intermediate layer that lies further from the center of the hair matrix
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The Hair Growth Cycle
Hair grows and sheds according to the hair growth cycle
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33 mm per day
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It is a recycling and
production of new hairs just in skin reproduction
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Types of Hairs
Lanugo) fine unpigmented new hair
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Hair Color
Differences in structure and variations in the pigment produced by melanocytes at the hair
matrix are what produce hair color
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This requires the rupture of secretory cells
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Is a mixture of triglycerides, cholesterol, proteins, and
electrolytes
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Sebaceous follicles) are large sebaceous glands that are not associated with hair follicles
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We have these follicles on the face, back, chest,
nipples, and the external genitalia
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They secrete their products into hair follicles
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Surrounding the secretory cells in these glands are special myoepithelial
cells that contract and squeeze the gland, causing sweat to discharge
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Merocrine Sweat Glands) also known as eccrine sweat glands
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They are smaller but more numerous than apocrine sweat glands
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It is called sensible perspiration because we can feel
it
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Its
pH range is of 4
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8
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2
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Cerumous glands) are modified sweat glands in the passageways of the external ear
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Chapter 5:

5-9
Nails are keratinized epidermal cells that protect the tips of the
fingers and toes
Nails) protect the exposed dorsal surfaces of the fingers and toes
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Lateral nail grooves) the depressions on the sides of the nail where there are lateral nail folds
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Nail root) where nail production takes place
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5-10
Several phases are involved in repairing the integument
following an injury
The integumentary system can function independently
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Basale cells replace epidermal cells and mesenchymal cells replace lost dermal cells
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Phases of integument repair
1
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3
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Inflammatory---swelling, pain, redness
Migratory---blood clot or scab forms (granulation tissue)
proliferation---deeper potion of blood clot dissolve and number of capillaries decline
Scarring---formation of inflexible, noncellular scar tissue completes the process

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Chapter 5:

Keloid) thick, raised area of scar tissue covered by shiny, smooth epidermal surface

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