You can see the melanin in the melanocytes in the stratum basale (indicated by the green arrow).
Functions:
1. protection of underlying tissues
2. temperature regulation
3. excretion
urea and uric acid in sweat
4. Synthesizes vitamin D with UV
light
5. Communication
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General Characteristics of the epidermis
1. Most superficial layer of the
skin
2. Stratified
squamous epithelium
3. No vascularization
Layers of the epidermis
1. Stratum basale/germinativum
(red arrow in picture below)
a.
deepest layer of the epidermis; lies on the upper portion of the
dermis
b. gets adequate
nourishment from under lying vascular tissue in the dermis
c. this layer
contains stem cells that divide and produce the more superficial layers
as daughter cells are pushed toward the
surface
d. one layer of
columnar or cuboidal shaped cells
2. Stratum spinosum (light
blue bracket)
a.
superficial to the stratum basal and deep to the stratum granulosum
b.
gets adequate nourishment from under lying vascular tissue in the dermis
c.
in older slide preparations the cells would appear spiky
d.
more division occurs here
3. Stratum granulosum (green
arrow)
a. three to 5 layers of cells superficial to the stratum spinosum
b. cells
are flattened and appear as a dark band
c. in the upper
border of this layer the cells are beginning to die & organelles are
deteriorating
d. the cytoplasm
is filling with granules
i. lamellated granules
contributes to waterproofing
ii. keratohyaline granules
form keratin fibrils
contributes to toughness
4. Stratum lucidum (black arrow)
a. clear layer
b. has mostly keratinocytes
c. only present in thick skin
5. Stratum corneum (dark
blue bracket)
a. "horny layer"
b. most superficial
20-30 cell layers
c. makes up most of
the thickness of the epidermis
d. cells are dead and
flattened
e. this layer is being
rubbed off and replaced
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Photo by Dr. W. Coons
You can see the melanin in the melanocytes in the stratum basale (indicated
by the green arrow).
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Layers of the dermis
1. Papillary layer
a.
Most superficial layer of the dermis
b. Has lots of areolar CT
c. Dermal papillae
i. uneven "nipple" like projections
ii. responsible for fingerprints
d. Has lots of capillary networks
e. Contains pain and touch receptors
2. Reticular layer
a.
The deepest layer of the dermis
b. Characterized by lots of dense irregular CT
(mostly collagen fibers for strength with a few elastin fibers for elasticity)
c. Contains many arteries
and veins, sweat and sebaceous glands and pressure receptors
d. This layer looks much more "messy" than the pappilary layer
Photo taken by Dr. W. Coons
The black bracket indicates the papillary layer and the blue bracket
indicates the reticular layer of the dermis. (100x)
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Photo taken by Dr. W. Coons
Meissner corpuscle in a dermal papillae at 100x
Photo taken by Dr. W. Coons
Meissner corpuscle in a dermal papillae at 200x
Photo taken by Dr. W. Coons
Meissner corpuscle in a dermal papillae at 400x
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Photo taken by Dr.
W. Coons
Black arrow-hair; blue arrow -arrector
pili muscle; green circle - sweat glands;
green arrow - sebaceous gland
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