Biology 322 Human Anatomy I

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Biology 322Human Anatomy I

• Integument

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Functions of Integumentary System (skin its
products)
Barrier to keep water and solutes in Barrier to
keep bacterial, dirt, etc. out Protection against
abrasion Contains sensory receptors for touch,
temperature, pressure, pain, etc. Temperature
regulation via hair, sweat, amount of blood
flow Blood reservoir Synthesis of vitamin
D Excretion
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Three Layers of skin
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Epidermis Avascular.
Depends on blood vessels in underlying
dermis for its nutrition
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(Epidermis)
Many layers of flat, dead, scale-like
cells full of keratin
One or two layers of dying cells
Not present in thin skin
Three or four layers of cells
Actively
synthesizing protein
keratin
Three or four layers of cells
Some cell division
Single row of dividing cells
(Connective tissue)
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Primary cell type in epidermis
which produce large amounts of protein
Other cell types
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Two related forms of melanin
Black or brown
Responsible for dark skin or hair
Red or pink
Responsible for pink skin (lips,
nipples, glans of
clitoris or penis, freckles) and
red hair Both synthesized
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(Epidermis)
Keratinocytes move from stratum basale to stratum
corneum, dying as they do so. Average 5 - 6
wks
- Keratinocytes in stratum basale ( stratum
spinosum) lie along basement membrane
divide by mitosis
- Older ones pushed toward surface by newer cells
- Melanocytes transfer melanin to keratinocytes
- Keratinocytes synthesize large amounts of
keratin and flatten out as they move toward
surface
- Older cells die but remain attached to each
other
- Cells eventually shed from stratum corneum
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Dermis
Two Layers
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Dermis Dense irregular connective tissue. Thus
Cells Fibers
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Dermis
Contains many types of sensory receptors for
touch, pressure, vibration, pain, temperature,
etc.
Some simple nerve endings Others complex
structures with multiple cell types
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Appendages of the skin
All begin as epidermis of embryo grow down into
dermis
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Hair - Distribuled over all skin except palms
of hands
soles of feet
nipples

glans of penis clitoris
minor labia -
Formed in follicles located deep in dermis -
Consists of layers of dead, highly keratinized
keratinocytes
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Black or brown
Blond
Red
Gray or White
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Each hair is associated with
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Sweat Glands
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Two specially modified sweat glands
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Sebaceous (oil) glands - Branched tubular
glands - Duct opens into opening of hair
follicle - Secretes sebum, consisting of
lipids, proteins, ions, carbohydrates,

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Nails - Tips of fingers and toes - Thick
layer of densely packed keratinocytes -
Produced by
Deeper layers of epidermis
Average growth 0.5 mm per week
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Carcinomas (cancers) of the skin
Basal Cell Carcinoma Keratinocytes of
stratum basale proliferate, invade dermis
Relatively low malignancy
Squamous Cell Carcinoma Keratinocytes of
epidermis proliferate. May invade dermis
Moderate malignancy
Malignant Melanoma Melanocytes of epidermis
proliferate, invade dermis Highly
malignant