BIOL 225, CH 6

The 3 major regions of the skin (integument):

the epidermis is composed of what types of cells?

undifferentiated cells found only in the stratum basale that divided and give rise to keratinocytes

cells that synthesize keratin and make up a great majority of the epidermal cells

cells that appear only in the stratum basale; they synthesize the brown to black pigment melanin which shields the DNA from UV radiation

cells that are associated with an underlying dermal nerve fiber

cells found in the stratum spinosum and stratum granulosum (800 per sq mm). they are macrophages that originate in the bone marrow but migrate to the epidermis and epithelia of the oral cavity, esophagus and vagina. when invaders are detected they alert the immune system.

list the layers of the epidermis from deep to superficial

•Very thick stratum corneum
•No hair
•Deep/High derma ridges
•No Sebaceous glands
•Numerous eccrine glands

•Lots of blood vessels
•Nutrients for Epidermis
•Thermoregulation
•Sensory Receptors
-the two layers are?

where nerve endings called thermoreceptors regulate body temp by sending signals to the brain, which then sends them back to the dermal blood vessels. types?

when cold, blood vessels narrow and reduce the blood flow close to the skin surface reducing heat loss

when overheated, blood vessels widen increasing cutaneous blood flow which increases heat loss

a thin zone of areolar tissue in and near the dermal papillae. this loosely organized tissue allows for mobility of leukocytes and other defenses agains organisms introduced through breaks in the epidermis

–80% of skin thickness
–Dense irregular connective tissue
–Vascularized
–Collagen and Elastin fibers, Pacinian Corpuscles, Hair follicles, Sebaceous glands and Sweat glands

subcutaneous tissue that pads the body and binds the skin to the underlying tissues. drugs are injected into it because it is highly vascular making it able to absorb them quickly. adipose tissue serves as an energy reservoir and thermal insulator.

the three pigments of skin color are

Made by Melanocytes
Taken up by Keratinocytes
–Variation in Color
•Eumelanin - brown to black pigment
•Pheomelanin - yellow to red
–Variation in amount of melanin/cell
–Variation in duration
–Production stimulated by UV light
–Freckles & pigmented moles

a yellow to orange pigment acquired from diet, most obvious in palms and soles

red pigment of blood; is enhanced when surface blood vessels are dilated

leading cause of accidental death, treated by fluid replacement and infection control

damages epidermis only, symptoms are local redness, swelling, and pain. heals in a few days and seldom leaves scars

damages epidermis and upper dermis, symptoms are redness, swelling, pain, and blisters. takes 2wks-mths to heal and may leave scars

damages epidermis and dermis and destroys nerve endings causing no initial pain. burned area is gray-white, red, or black and skin often requires skin grafts

what are the three types of skin cancer?

skin cancer that is:
•Least malignant, most common
•Stratum basale cells proliferate, invade dermis & hypodermis
•Slow growing, rarely metastasize
•Surgical excision 99% successful

skin cancer that:
•Arises from keratinocytes of stratum spinosum
•Usually on scalp, ears, and lower lip
•Grows rapidly, metastasizes if not removed
•Good prognosis with radiation therapy or surgical removal

•Cancer of melanocytes - the most dangerous
–Highly metastatic
–Resistant to chemotherapy
Treat with wide surgical excision and immunotherapy