Exercise 7 - OBJECTIVES
1. Describe several important functions of the skin, as part of the
integumentary system.
2. Identify, describe the anatomy, and characterize the distribution
of the following skin structures:
a. Epidermis
1. Stratum corneum
2. Stratum lucidum
3. Stratum granulosum
4. Stratum spinosum
5. Stratum basale
b. Dermis
1. Papillary
2. Reticular layers
Exercise 7 - OBJECTIVES
2. Identify, describe the anatomy, and characterize the
distribution of the following integumentary structures:
a. Hair follicles and hair
b. Sebaceous glands
c. Sweat glands
d. Pacinian corpuscles
e. Merkel cells and Merkel discs
f. Meissner’s corpuscles
3. Compare and contrast the properties of the epidermis to the
dermis.
4. How do sweat glands and sebaceous glands differ?
5. Compare and contrast the anatomy and function of the eccrine
and apocrine sweat glands.
6. Describe what determines skin color.
7. Describe the function of melanin.
SKIN LAYERS
Epidermis
Dermis
X
Marieb; Fig. 5.1
X
http://www.sunyniagara.cc.ny.us/val/histology.html
Major Layers of
the Integument
White arrows –
epidermis
Blue arrow - dermis
Red arrows – dermal
papillary layer
(primarily loose
connective tissue)
Green arrows – dermal
reticular layer
(primarily dense
irregular connective
tissue)
Black arrow –
hypodermis (superficial
fascia) (not part of
the “skin”)
SKIN LAYERS
Epidermis
Dermis
Stratum corneum
Papillary layer
Stratum lucidum
Reticular
layer
(maybe)
Stratum
granulosum
Stratum spinosum
Stratum basale
Marieb; Fig. 5.2
So, name the layers,
and define their
basic characteristics.
epidermis
 keratinized
 stratified
squamous epithelium
dermis
 strong, flexible
connective tissue
What are the names of the
epidermal layers of thin skin?
stratum corneum
stratum granulosum
stratum spinosum
stratum basale
What are the names of the
epidermal layers of thick
skin?
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
Dermal Papillary
Dermal Reticular
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
Meissner’s corpuscles
Epidermis of
Palm of Hand
Green arrow –
epidermis of thick skin
Red dashed line –
epidermal ridges
projecting into the
dermis to protect from
shear forces on the
skin
Yellow dashed line –
dermal papillae
projecting into the
epidermis also provided
for strength against
shear forces
Epidermal Layers of
Palm of Hand
Black arrows – stratum
corneum, where cells
have lost their nuclei
Green dotten lines –
stratum granulosum
Yellow arrows – stratum
spinosum
White arrows – stratum
basale (also called
stratum germinativum)
single row of cells are
constantly undergoing
mitosis and giving rise to
the overlying epidermis
Closer View of
Epidermal Layers of
Palm of Hand
Green arrow – stratum
corneum
Red arrows – lightly
staining stratum lucidum
(ONLY PRESENT IN
THICK SKIN)
White arrows – darkly
staining stratum
granulosum
Yellow arrow – stratum
spinosum
Stratum spinosum
Stratum basale
Meissner’s corpuscle
Close-Up of
Stratum Spinosum
Red arrows – desmosome
“spines”
Primary Epidermal
Cells
Keratinocytes
Melanocytes
Langerhans’
Merkel
 predominant
cell type
 spider-shaped
 star-shaped
(epidermal
dendritic cells)
 shaped like
spiky
hemisphere
 arise from
bone marrow
and migrate to
epidermis
 functions in
sensation
 produce
keratin
 connected to
one another by
desmosomes
 arise in
stratum basale
and are
“pushed”
upward
 produce
melanin that is
then transferred to
keratinocytes
 found in
deepest layers
 macrophages
that help
immune system
 located at
epidermaldermal
junction
So, name the epidermal cells
and define their
basic characteristics.
keratinocytes
Remember, these are the most
predominant cell type in the
epidermis. They are first produced
at the level of the stratum basale,
but then get ‘pushed’ to the
surface. As they move ‘upwards’,
they lose their organelles, and
become somewhat hardened. So,
the stratum corneum consists of
dead keratinocytes that are ready
to be sloughed off.
In other words, these
keratinocytes are
anucleated. You
should remember this
concept from the
information provided
on the histology of
epithelial tissue in
Exercise 6A. The
next slide is from
this Exercise. If
this is not familiar
information, go back
and review all of
these slides.
Pushed to surface
Note how the
keratinocytes at this
level have lost their
nuclei.
STRATIFIED
SQUAMOUS
EPITHELIUM OF THE
SKIN
Green line – nucleated
non-keratinized cells
Yellow line –
nonnucleated
keratinized cells
Blue line – depth of
entire epithelium
Pigmented
keratinocytes
http://www.usask.ca/anatomy/teaching/anat232/Integument.jpg/II55%20Pig.%20keratinocytes%20HP.jpg
Note the keratinocytes
filled with brown
pigment.
So, name the epidermal cells
and define their
basic characteristics.
melanocyte
Remember, these are the cells that
produce melanin, which is the
pigment that protects many of the
cells in the epidermis.
Once produced, melanin is actually
phagocytosed by the keratinocytes.
Do you see the “dots” in the
keratinocytes that are located near
the melanocytes?
melanin-containing
keratinocyte being ‘pushed
toward the stratum corneum
keratinocyte undergoing
mitosis AND
accumulating melanin
melanocytes
http://cal.vet.upenn.edu/histo/skin/melanocytes.html
Melanocyte
http://www.usask.ca/anatomy/teaching/anat232/Integument.jpg/II53%20Melanocyte%20HP.jpg
Melanocyte
http://www.usask.ca/anatomy/teaching/anat232/Integument.jpg/II53%20Melanocyte%20LP.jpg
Melanocyte
http://www.usask.ca/anatomy/teaching/anat232/Integument.jpg/II-54%20Melanocyte.jpg
http://www.wtmcgee.com/img/suntan.jpg
So you should now be able to explain why a suntan ‘fades’.
The keratinocytes that had the melanin are ‘pushed’ to the
surface of your skin, and are sloughed off.
Which of these two
individuals has a greater
number of melanocytes?
People of all skin colors have
about the same number of
melanocytes.
Differences in skin color
result from differences in the
synthesis of melanin and how
‘clumped’ the melanin is within
the keratinocytes.
http://photos.imageevent.com/dreamkast/rocket
s/dreaming.jpg
So, name the epidermal cells
and define their
basic characteristics.
Langerhans’
Remember, these are the epidermal
dendritic cells. They are phagocytic
and play a role in immunity.
This should make sense to you. Since
the skin is the first structure that is
often encountered by a foreign
pathogen, we should have a way to
defend ourselves at this level.
Close-up of a Langerhans’ cell.
http://www2.uibk.ac.at/fakultaeten/c5/c552/histologie-molekularezellbiologie/arbeitsgruppe-pfaller-en.html
So, name the epidermal cells
and define their
basic characteristics.
Merkel Cell
Remember, these are the tactile cells.
They are receptors for light touch.
The Merkel cell and the associated
nerve fiber are collectively called a
tactile (Merkel) disc.
SKIN LAYERS
Epidermis
Dermis
Stratum corneum
Papillary layer
Stratum lucidum
Reticular
layer
(maybe)
Stratum
granulosum
Stratum spinosum
Stratum basale
Dermis of
Thick Skin
Red arrow –
reticular layer of
dermis
Blue arrow –
papillary layer of
dermis
Green arrows –
Meissner’s
corpuscles in dermal
papillae projecting
into the epidermis;
respond to light
touch
Close-Up of
Meissner’s
Corpuscles
Blue arrows –
Meissner’s
corpuscles in dermal
papillae projecting
into the epidermis;
often described as
looking like cotton
candy; respond to
light touch
Stratum spinosum
Stratum basale
Meissner’s corpuscle
Meissner’s
corpuscle
Meissner’s corpuscle
Meissner’s corpuscles
Meissner’s corpuscles
Meissner’s corpuscle
Close-Up of
Pacinian Corpuscle
Blue dashed line
outlines Pacinian
corpuscle generally
located deep in the
dermis or in the
hypodermis; often
described as looking
like an onion;
generally respond to
deep pressure or
vibration
Pacinian corpuscle
http://www.usask.ca/anatomy/teaching/anat232/Integument.jpg/II57%20Pacinian%20corpuscle.jpg
Pacinian corpuscle
Pacinian corpuscle
Pacinian corpuscle
Pacinian corpuscle
Cutaneous Glands
Sebaceous Glands
Sweat Glands
Eccrine Glands
Apocrine Glands
Marieb; Fig. 5.3
Cross Section
of Epidermis
and Dermis
Blue arrows –
longitudinal section
of eccrine sweat
duct which is a
simple, coiled,
tubular structure.
The secretory
part lies coiled in
the dermis; the
duct extends to
the skin surface
to open into a
pore.
Reticular Layer
of Dermis
Red arrow – eccrine
sweat duct (you
should not be
surprised that this
duct is lined with a
stratified cubiodal
epithleium)
Blue arrows –
eccrine sweat glands
Eccrine sweat
gland duct
http://www.usask.ca/anatomy/teaching/anat232/Integument.jpg/II53%20Sw.%20gl.%20duct%20port.%20HP.jpg
Eccrine sweat
gland secretory
portion
Eccrine sweat
gland duct
http://www.usask.ca/anatomy/teaching/anat232/Integument.jpg/II53%20Sw.%20gl.%20duct%20port.%20LP.jpg
Eccrine Sweat gland
Eccrine Sweat
gland duct
Eccrine
Sweat gland
Eccrine
Sweat gland
Close Up of
Eccrine Sweat
Gland
Red arrow – eccrine
sweat duct
Blue arrow – eccrine
sweat glands
Thin Skin
Red arrows – epidermis
of thin skin
Black arrows – hair
follicle (without the
hair)
Green arrow – arrector
pilli smooth muscle
Blue arrow – sebaceous
gland (remember that
their ducts usually
empty into a hair
follicle)
Hair
Red arrow – hair follicle
shaft
Blue dotted line – bulb
of hair follicle
Hair
Green arrows – hair
follicle shaft
Red arrows – apocrine
sweat glands (noted by
very wide lumen); open
onto hair follicles
Hair Cross-Section
Red arrow – hair follicle
shaft
Green arrows – apocrine
sweat glands (noted by
very wide lumen)
http://www.sunyniagara.cc.ny.us/val/histology.html
http://www.sunyniagara.cc.ny.us/val/histology.html
Arrector pili muscle
Arrector pili muscle
Sebaceous gland
Arrector pili muscle
Sebaceous gland
Arrector pili
Eccrine glands
Sebaceous gland
Arrector pili
Sebaceous gland
Sebaceous gland
Sebaceous glands
Hair follicle and hair root
Eccrine gland
Apocrine gland
Apocrine gland
Eccrine gland
What kinds of glands
are the blue arrows
pointing to?
Larger lumen –
must be apocrine
What kinds of glands
are the red arrows
pointing to?
Small lumen –
must be eccrine
Which of these two
images is thick skin?
Thin skin?
Very thick
stratum corneum
and prominent ridges must be thick skin
Has hair follicles
and thin epidermis must be thin skin
The End.