UNIT 4 INTEGUMENTARY SYSTEM
SUBOBJECTIVES
4.1
4.2
4.3
4.4
4.5
4.6
I can explain how the cellular structures of the epidermal layers determine their function
I can explain how the skin responds to sun exposure and name the cells and cellular structures involved
I can describe the structures and functions of the dermis and hypodermis
I can explain how the structures of the accessory organs of the skin fit their function
I can explain how body temperature is regulated
I can describe how genetic, environmental, and physiological conditions determine skin color
Evolution connection
4.7 I can explain how fair skin and pheomelanin are an evolutionary compromise.
Vitamin D levels determined how human skin color evolved
http://www.nasw.org/vitamin-d-levels-determined-how-human-skin-color-evolved-1
It may seem the sun wages a constant war against our skin. Harmful UV radiation burns us, damages our DNA, and can sow the
seeds for melanoma. But the sun is essential to our healthy development and our immune systems, because sun-exposed skin
produces Vitamin D. During the long-ranging human exodus from Africa, says anthropologist Nina Jablonski, Vitamin D levels in
the body played a key role: driving the evolution of our species' skin color.
With receptors located in the cells of many major organs and in the immune system, Vitamin D helps in calcium absorption and
prevents aberrant cell division. UVB radiation catalyzes its creation in our skin.
According to Jablonski, “there is a conspicuous geographical pattern” between skin color and distance from the equator. At more
northern or southern latitudes, the level of UVB rays hitting Earth’s surface decreases due to the planet’s tilt. The equator is
bathed year-round in UVB rays, but seasonal variations mean that people in Northern Europe receive virtually no UVB exposure
in winters.
As a result, Jablonski said, humans living near the equator developed darker skin tones, while those in northern climates
developed lighter hues. High humidity also decreases UVB levels, as marked by the contrast between skin tones of early humans
living in dry equatorial Africa and moist equatorial South America.
The dearth of UVB rays in northern climates put positive evolutionary pressure on early migratory humans to ramp up Vitamin D
production, Jablonski noted. And indeed, fair-skinned people of European descent are nearly six times more efficient at making
Vitamin D from UVB rays than those living near the equator.
Different types of melanin pigments in skin trigger these variations. In dark-skinned people, eumelanin is dominant and acts as a
natural sunscreen; fairer-skinned individuals have much more pheomelanin. However, while pheomelanin produces vitamin D
efficiently, its reaction with high levels of UVB also makes dangerous free radicals — which damage skin cells over time.
Failing to produce adequate levels of Vitamin D can cause physical deformities, including painful distension of the pelvic bones in
women — and severe complications during childbirth. But even with persistent UV exposure, malignant melanoma doesn’t set in
until later in life. Its effect on reproductive success would have been almost nonexistent, Jablonski stated.
The process of long-term skin lightening, known as “depigmentation,” occurred due to a series of mutations in a gene called
SCL24A5, Jablonski said. That gene controls the size of melanin packets in skin and the types of melanin produced.
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“All of us can use this as a wonderful teaching tool,” she said. “We often wonder how we can teach evolution to our students, to
our children. What human examples can we bring that will be effective? Well, here’s one: human skin pigmentation. You don’t
need any teaching tools, because you’re wearing it."
READINGS: SUBHEADINGS
Pages 157-172
MORPHEMES TO MEMORIZE
http://quizlet.com/_et7vq
1)
2)
3)
Albwhite
Cutskin
DermSkin
4) EpiUpon, after, in addition
5) FollicSmall bag
6) Hol7) hole
8) Kerat-
9) horn
10) Melanblack
11) PorPassage, channel
12) Sebgrease
STRUCTURES TO MEMORIZE
http://quizlet.com/_g4406
Figure 6.3 page 161 memorize all structures
Figure 6.2a page 160 memorize all
structures
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Figure 6.4 page 162 memorize all structures
Figure 6.5a page 165
memorize all structures
OTHER VOCABULARY TO MEMORIZE
http://quizlet.com/_g43yq
4.1
1) Epidermis
Outer layer of skin composed mostly of stratified squamous epithelial cells. It protects the body from infection and
regulates water loss.
2) Dermis
Composed of dense irregular connective tissue. It cushions the body against stress and contains many integumentary
accessory organs.
3) Collagen
the most abundant protein in mammals. Found in the fibrous connective tissues of the skin and in many other
connective tissues
4) Basement membrane
anchors epithelium to loose connective tissue. It functions as a mechanical barrier impeding malignant cell metastasis.
5) Subcutaneous layer (Hypodermis)
loose connective tissue that attaches the skin to underlying organs
6) Keratinocytes
the most common cell type found in the epidermis
7) Keratinization
the accumulation of the fibrous protein that is the main structural component of skin, nails, and hair
8) Stratum basale
a single layer of rapidly dividing stem cells of the epidermis. It also contains melanocytes.
9) Stratum spinosum
many layers of cells with oval shaped nuclei that are beginning to flatten and keratinize
10) Stratum granulosum
3-5 layers of cells that have begun to loose their nuclei. They give skin its color.
11) Stratum corneum
Many layers of dead keratinized cells that protect the skin
12) Stratum lucidum
Found in the epidermis of the palms and soles of the feet. It is composed of clear nonnucleated cells of various
thicknesses, but it is usually thin.
4.2
13) Melanocytes
the cell type that produces the pigment that protects the skin from UV radiation
14) Melanin
Dark brown to black pigment that gives skin, hair, and eyes their color
4.3
15) Pacinian corpuscles
a nerve ending in the skin that responds to deep pressure
16) Meissner’s corpuscles
a nerve ending in the skin that responds to light touch
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4.4
17) Hair follicle
the organ that produces hair
18) Hair root
the portion of the hair embedded in the skin
19) Hair papilla
connective tissue and a capillary loop that nourishes the follicle
20) Hair shaft
compressed, highly keratinized, dead epidermal cells
21) Arrector pilli
smooth muscles that cause goose bumps (hair standing up) when they contract
22) Sebaceous gland
a gland that secretes an oily mixture that lubricates and waterproofs the skin and hair
23) Sebum
an oily mixture that lubricates and waterproofs the skin and hair
24) Sudoriferous gland
merocrine and apocrine sweat glands, and the specialized ceruminous, and mammary sweat glands
25) Eccrine sweat gland
the main sudoriforous gland type. They secrete mostly water and salt to cool the body.
26) Apocrine sweat gland
a sweat gland that secretes an oily mixture into a hair follicle. The decomposition of the mixture by bacteria causes the
unique smell of individuals.
27) Ceruminous gland
earwax producing organs. Their product mixes with sebum and dead cells. This substance keeps the eardrum (tympanic
membrane) pliable, and traps bacteria and particles.
28) Mammary gland
a modified sudoriferous apocrine gland that produces milk
4.5
29) Metabolism
30) all of the chemical reactions necessary for life. It includes breaking down and building molecules.
31) Homeostasis
maintaining internal conditions within a narrow range
32) Effector
responds to receptor causing a reduction in the stimulus
33) Receptor
something that detects a condition, such as body temperature, that is outside of normal parameters
34) Stimulus
a change in a physiological condition such as body temperature
35) Vasodilation
A widening of the diameter of a blood vessel.
36) Vasoconstriction
A decrease in the diameter of blood vessels caused by contraction of smooth muscles in the vessel walls.
37) Radiation
ionizing or nonionizing waves or particles that travel through a vacuum or through matter
38) Hyperthermia
elevated body temperature due to improper temperature regulation
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39) Hypothermia
low body temperature due to improper temperature regulation
4.6
40) Pigment granule
a vesicle packed with pigments such as melanin
41) Albinism
partial or complete lack of melanin
42) Jaundice
yellowing of the skin resulting from the liver failing to break down bilirubin, which is a byproduct of hemoglobin
catabolism
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