Lab Exercise 7
The Integumentary System
Portland Community College
BI 231
Skin
• Or Cutaneous membrane
is an organ.
• (an organ is a structure
that contains two or more
of the primary tissue
types)
• Embedded within the skin
are various accessory
structures the combination
of both is called the
integumentary system
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Skin
• Epidermis: Superficial layer
• Made of stratified squamous keratinized epithelium
• 4-5 Layers
• Dermis: Underlying connective tissue layer
• 2 Layers
• Hypodermis: Not part of the skin, it is deep to
the dermis
• Primarily adipose tissue
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Layers of the epidermis
Stratum basale: single row of cells
•
Adjacent to the dermis
and attached by the
basement membrane.
•
Constantly dividing and
pushing up layers
•
Melanocytes with
melanin protects the skin
from UV radiation
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Layers of the Epidermis
Stratum spinosum: several
cell layers superficial to
stratum basale.
•
Cells also dividing
•
Cells contain bundles of
intermediate filaments
made of pre-keratin
•
Cells appear star-shaped
because the cell
membrane pulls away
from the other cells,
except in areas where
desmosomes are.
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Layers of the Epidermis
Stratum granulosum:
•
•
•
The upper part of this layer has cells that are
beginning to die
Lamellated granules contain a waterproofing
glycolipid that is secreted into the extracellular
space
Keratohyaline granules combine with intermediate
filaments to form keratin fibrils
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Layers of the Epidermis
Stratum lucidum: Thin
translucent layer of
dead keratinocytes
•
Found only in thick
skin
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Layers of the Epidermis
1. Stratum corneum:
Outermost layer
•
•
•
•
20-30 cell layers
thick
Cells are dead and
flattened
Full of keratin
Constantly being
rubbed off
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Epidermis cell phases
• Deepest layer (basale) goes through rapid
division.
• Middle layers undergo a process of
producing precursor molecules that lead to
waterproofing of the cells.
• The final phase is the completion of the
waterproofing process. Cells eventually
die, providing a tough barrier
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Dermis
•
The dermis is the connective tissue layer under the
epidermis.
Composed of primarily of fibers:
•
•
•
•
•
Irregularly arranged collagen fibers make up the majority
and provide strength and flexibility to skin
Lesser numbers of elastic fibers which provided elasticity
to the skin
There are also reticular fibers found in the dermis
blood vessels, nerves, sensory receptors, hair follicles and
glands.
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Dermis
1. Papillary Layer: Superficial dermal region
•
•
•
•
Areolar connective tissue
Contains capillaries, lymphatics and sensory neurons
Dermal Papillae: the fingerlike projections from the
superior surface
Epidermal ridge: The epidermal layer that dips down
into the dermal papillae
• Create fingerprints
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Epidermis
Epidermal ridge
Papillary
Layer
Dermal Papillae
Reticular
Layer
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Finger Prints
Epidermal
Ridge
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Dermis
2. Reticular Layer: Deepest skin
layer
• Dense irregular connective
tissue
• Contains the arteries, veins,
sweat and sebaceous glands
• Cleavage lines: the deep
creases (like in the palm)
where collagen and elastic
fibers are arranged in
parallel bundles.
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Hypodermis
Dermis
• Subcutaneous layer
that is not part of the
skin
• Beneath the dermis
layer
• Composed of adipose
and areolar connective
tissue
Hypodermis
• Highly vascular
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Cells of the Epidermis
• Keratinocytes: The main cells of the epidermis
• Produce keratin, water proof protein
• As new cells form, they push the older cells toward
the surface, where they gradually accumulate
keratin and eventually die
• Melanocytes: Spidery black cells
• In stratum basale
• Produce melanin, the pigment that protects skin
from UV damage
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Cells of the Epidermis
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Meissner’s (Tactile) Corpuscle
• Located in the dermal papillae
• Receptor for light touch
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Merkel Cells
• Merkel Cells: At the junction of the sensory
nerve endings
• In upper dermis and ll
lower epidermis
Light touch (like fly
walking over cheek)
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Pacinian (Lamellated)
Corpuscle
•Lie deep in the dermis
•Respond only when deep pressure is first applied
•Monitor high frequency vibrations
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Other skin receptors
• Warm and cool receptors: When you are at
comportable temperature both of these are
firing
• If you increase or decrease the skin
temperature beyond the range of these
receptors, pain receptors are stimulated.
• Pain receptors are naked nerve endings in
the dermis that respond to numerous
environmental stimuli.
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Integumentary Glands
• Sudoriferous (sweat)
glands
• Lactiferous (milk)
glands
• Sebaceous (oil) glands
• Ceruminous (earwax)
glands
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Eccrine (Merocrine) Sweat Glands
• Eccrine sweat glands
• Ducts open directly on
the surface of the
epidermis
• Produce normal body
perspiration.
• Reduces body
temperature by
evaporative cooling
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Apocrine Sweat Glands
• Apocrine glands: secrete a water and
a higher concentration of organic
acids than eccrine glands that
bacteria can use for nutrients
(creates body odor)
• Found in the armpits, around nipples
and in the pubic region
• Secrete products into hair follicles
or directly onto the surface.
• Begin functioning at puberty
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Apocrine
Sweat Glands
• Red arrow Apocrine Sweat
Glands
• Green arrow Hair follicle
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Sebaceous
Glands
• Sebaceous glands
• Produce oily
substance called
sebum
• Helps waterproof
the skin
• Acne: infection of the
sebaceous gland
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Hair
• Keratinized cells
produced in
• Hair follicles:
tubular
compartments
that contain
hair(projections
of the epidermis
into dermis)
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Hair
• Bulb: deepest portion
of the hair follicle
• Bulb contains the hair
matrix which contains
actively dividing cells
• The actively dividing
cells give rise to the
hair root.
As hair root approaches
the surface of the skin it
becomes the hair shaft.
Hard Keratin covers the
hair
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Hair Histology
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Arrector Pili Muscle
• Arrector pili muscle: Smooth muscle that pull hair
upright during fright or cold (goose bumps)
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Hair
• Determinate hair grows
to a specific length and
then stops
• Found in axilla, groin,
eyelashes and eyebrows.
• Indeterminate hair grows
without regard to length.
• Found on scalp and beards
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Hair
• Medulla central portion of
the hair which is enclosed
by an outer cortex.
• The cortex may contain
pigments which give the
hair its color (melanin)
• The cuticle is superficial
to the cortex
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Fingernails
•
•
•
•
•
Scale like modification of the epidermis
Free edge: part that grows away from the finger
Body: The nail
Root: Embedded in skin and sticks to the nail bed
Nail Bed: Extension of the stratum basale beneath the
nail
• Nail Matrix: Proximal part of the nail bed responsible
for nail growth
• Lunula: white crescent area; Most active growth region
of nail matrix
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Fingernail
Structures
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Muscle Tissue
• Like epithelial tissue,
muscular tissue is a
cellular tissue with the
tissue having mostly
cells and little matrix
• There are three types
of muscle: skeletal,
cardiac and smooth
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Skeletal Muscle
•
•
•
•
Cells called fibers
Striated
Voluntary
Multinucleate
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Sarcomere
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Cardiac Muscle
• Striated but striations are
much less obvious.
• Cardiac muscle cells are
called myocytes.
• Branched
• Involuntary
• Intercalated discs, which
facilitate the transmission
of the electrical impulses
in the heart
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Smooth Muscle
• Nonstriated
• Involuntary
• Cells of smooth
muscle are spindleshaped
• Found in intestine
where it propels food
along by a process
known as peristalsis
and segmentation
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The End
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