Integumentary System- Chapter 3.2 

integumentary system- largest organ of the body that forms a physical barrier between the external environment and the internal environment that it serves to protect and maintain %%(skin)%%

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Functions:

Skin is also critically important in %%regulating body temperature%%, due to the extensive array of tiny capillaries and sweat glands that lie near the surface of the skin.

It is also involved in certain %%chemical processes%% in the body.

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Keratin:

keratin- a %%tough protein%% also found in hair and nails that adds structural strength, helps to protect the skin against damage

keratinocytes- produce keratin

• Keratin and naturally occurring oils in the skin assist in serving as a %%water barrier%%, and keratin prevents water from entering the body during bathing or swimming.

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Melanin:

Melanocytes- produce %%melanin%%, a pigment that %%protects%% the body from harmful %%UV radiation%%

Melanin- primarily responsible for %%human skin color%%

• Exposure to sunlight causes melanocytes to produce more melanin.

Freckles- clusters of melanocytes

Albinism- %%prevents the normal production%% of melanin, and produces very little pigment in the skin, hair, and eyes.

• Light skin is good for rapid Vitamin D production, and dark skin is better for protection from Atoo much UV.

  

Appendages of the Skin:

Sweating:

Process of sweating- the body %%eliminates chemical waste%% products, including urea, uric acid, and salts

sudoriferous glands- distributed in the %%dermis%% over the entire body (%%sweat glands%%)

eccrine glands- the major sweat glands of the body, cover most of the body, open directly onto the skin

• fluid secreted by the sweat glands is acidic, and helps to protect the body against bacterial infections

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Sebum:

sebaceous glands- located all over the body except for the palms of the hands and soles of the feet, produce an oily substance called %%sebum%%

sebum- an oily and slightly waxy substance found on the skin, helps to keep the %%skin and hair soft%%but also contains chemicals that kill bacteria \n

Anatomy of the Skin:

Epidermis:

Epidermis- the surface epithelium of the skin, overlying the dermis.

• The epidermis contains five layers of tissue.

• From superficial to deep (the outside going in), these are the %%stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale%%.

• The epidermis completely replaces itself every 25 to 45 days.

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Layers of the Epidermis:

Stratum Corneum- the %%oldest%% layer of cells

dust- (dead) cells that %%shed%% from the stratum corneum

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Stratum Lucidum- %%clear%% layer of dead, keratinized cells

• This is only present in areas of the body with %%thick skin%%.

Epidermal Ridges- %%increases surface area%% for oxygen, diffusion from the dermis

• This causes finger and footprints to be made.

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Stratum Granulosum- produces a large amount of %%keratin%%, die eventually due to %%lack of oxygen%%

Stratum Spinosum- cells begin forming desmosomes to attach to each other in layers.

Stratum Basale- deepest layer with melanocytes

• Merkel cells- located in the stratum basale, function as %%touch receptors%%

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Cells in the Epidermis:

Epidermal dendritic cells- respond to the presence of foreign bacteria or viruses by initiating an immune system response

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Dermis:

Dermis-  thick layer of living tissue below the epidermis which forms the true skin, containing blood capillaries, nerve endings, sweat glands, hair follicles, and other structures

Papillary Layer- dermal papillae that %%protrude%% from the surface up into the epidermis

Reticular Layer- collagen and elastic fibers in this region have an %%irregular arrangement%%, it includes blood and lymphatic vessels, sweat and oil glands, involuntary muscles, hair follicles, and nerve endings

• When the two %%separate%%, they form %%blisters%%, or a “fluid filled pocket".
• Some of the dermal papillae contain capillaries that supply nutrients to the epidermis. Other dermal papillae contain nerve endings involved in sensing touch and pain. \n

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Hypodermis:

Hypodermis (subcutaneous fascia)- a %%storage%% repository for fat

• %%not a part of the skin, but connects%% the skin to the underlying tissues

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Nails:

Nails- a more compacted, keratinized version of the stratum %%corneum%%

Cuticle- overlap of the stratum corneum, %%keeps bacteria away%% from nail root

Bed- contains tissue from stratum basale and spinosum

Matrix- contains cells that constantly divide

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