The color of the skin comes form three classes of (skin) pigments:
-Pheomelanin (yellow to red)
-Eumelanin (brown to black)
What are the two kinds of melanin?
pheomelanin, which is yellow to red
euelanin, which is brown to black
in hair these (granules) are scattered among the keratin fibers
in skin, these pigments are found in cells called melanocytes
Almost everyone has roughly the same number of melanocytes
difference in skin color is deturmined by the amount of pigment in each melanocyte.
_________ is made from the amino acid tyrosine in an organelle called ___________. The pigment is _______ to keratinocytes, giving ______ and _____ there color
melanin, melanosome, transferred, hair, epidermis
A mole (or nevus) is formed when:
melanocytes accumulate in ine region
True ore false: Melanocytes are normally scattered more-or-less throughout the epidermis
mostly in deeper areas (spinosum and basale)
In light-skinned persons...
little melanin is made and stored in melanocytes
in theses people the color of the skin is predominantly due to hemaoglogin
a red pigment in blood that gives the skin a pinkish cast.
a precursor to vitamin A
found in intensely colored fruits and vegetables.
there was a plummer who ate so many carrots and tomatoes this his skin turned orange
In some diseases, such as _______ ______, the pigment ________ accumulates in the _____, giving it a yellow color.
liver failure, bilirubin, skin
A symptom of liver disease
symptom of turning yellow (particular easy to see in the "whites" of the eyes)
A dense connective tissue layer beneath the epidermis
There are few cells
it is mosly collagen and elastic fibers
There are two regions of the dermis
When the ______ of farm animals is chemically treated it is called ______.
superficial portion of the dermis (about 1/5 its thickness)
consists of areolar connetive tissue with thin collagen and fine elastic fibers
contains dermal ridges that penetrate up into the epidermis
each of these tend to contain capillaries, blood vessels and sensory structures known as Meissner corpuscles and free nerve endings
What are the functions of Meissner corpuscles?
Sensing light and touch
What are the functions of free nerve endings?
sensings pain, temperature, and itch
The _________ region is important for its _____ attachment to the epidermis. Also on the ______, ______, and soles of the feet, the underlying structure of the dermis causes the skin to have ____________.
papillary, tight, palms, fingertips, fingerprints
The deeper portion of the dermis (about 4/5 of its thickness)
Consists of dense irregular connective tissue with bundles of thick collagen and some coarse elastic fibers.
Spaces between fibers contain some adipose cells, hair folicles, nerves, sebaceous glands, and sudoriferous glands
True or false: The dense connective tissue of the drmis is strong and resilient; it can be sretched, and it snaps back to its original form.
What are striae ?
More commonly known as "stretch marks"
Tears in the dermis caused by stretching, i,e: obesity or pregnancy
these are seen on the skins surface.
(not tipically included in the skin proper)
A loose connective tissue made up of areolar and adipose tissues
Blood vessels pass through this layer on their way to the dermis.
Lamellated (Pacinian) corpuscles, a kind of nerve ending mediating the felling of vibration, are found in the lower dermis and upper part of the this layer
common place to give injecitons
abbreviated - subQAn example of an areolar connective tissue
Areolar connective tissue
a loose conedtive tissue made up of collagen, reticular and elastic fibers
witha adipose (fat) cells suspended in the fiber matrix
Where is adipose tissue (fat) located?
the subcutaneous layer of the skin
What are the Sensory Receptors/Sensory Nerve Endings?
1. Meeisner (touch) corpuscles: light touch
2. Merkel (tactile) disks: light touch
3. Free nerve endings: pain & temp, itch, hair movement
4. Pacinian (lamellated) corpuscle: deep pressure, vibration
Also sensation from nerve nerworks around hair roots in thin skin
At the interface between epidermis and dermis, in the papillary region, are the ...
...Meissner corpuscles, Merkel discs, and free nerve endings.
Deep in the skin, at the border of the dermis and the subcutaneous layer, is the _______ ________ _______.
Pacinian (lamellated) corpuscle.
these are layered like and onion
this special shape means that the nerce ending inside the responds preferentially to vibration.
Scientist believe that the actual finciotn of ________ ______ is to detect the slippage of thick skin (_____ and _____)against a surface, as when you lose your grip on a branch. As the hand slips, its alternate grabbing and _______ causes a _______ against the branch, signalling an importantg message: "Your going to fall, dude"
"vibration" receptors, fingers, palm, slipping
What are the two types of Sweat Glands (sudoriforous Glands) present in the skin?
Eccrine sweat glands
Apocrine sweat glands
Eccrine Sweat Glands
used to cool skin (control temp) and restore homeostasis
they lie in the dermis and open to the skins surface through a duct
secrete a sweat that is thin: dilute solution of salt water with reaces of urea, uric acid, ammonia, amino acids, glucose, and lactic acid
The water is needed for evaporative cooling of skin
The rest are waste products being released
these glands are active throughout life.
See table in obj. 11(p.367)
Apocrine Sweat Glands
Do not open to the skin, but are associated with hair follicles
dont use apocrine secretion
more viscous secretion than eccrine sweat glandsThey are stimulated to release their product during emotional stress and sexual exitement-(not active untill after puberty)
they lie int the subcutaneous layer, and there are traces of fat-soluble substances ( such as pheromones) that are part of the sexual response.
See table in obj. 11(p.367)
most often found opening onto the neck of the hair follicle
oilly secretion, called sebum, coats and protects the hair surface against drying and breakage
Become active at puberty in response to androgens. (yes females produce small amounts of androgens.)
_________ glands found on the lips, and other hair-free surfaces ______ directily into the ________ of the skin.
Sabaceous, open, surface
True ore false: Acne is an inflamation of the sebaceous glands
Some types of _________ like living in _______, and acne occurs predominately in __________ follicles that are colonized by _________.