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7/28/2019 3BIO 261 Skin Lecture_SP 2011
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Skin(IntegumentarySystem)
PLEASE NOTE: Only images surrounded by a thick black
border in the following lecture slides will be included on
Practical 1. The skin model at the end of this lecture
series is also fair game for P1.
APR 3.0 Module 4. Integumentary
Histology & Dissection Sections
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Skin (Integument) Outer covering of the body
Largest organ of the body An organ is a group of
tissues that work together
and have specific functions.
Functions of the skin:
Protection = Barrieragainst drying, bacteria,
UV light, water, physical
abuse
Temperature regulation
Sensory perception
Excretory organ
Formation of vitamin D
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Consists of three major
regions:
1. Epidermis
Outermost
superficial region
2. Dermis
Middle region
3. Hypodermis
(Subcutaneous) Deepest region
Skin (Integument)
APR 3.0 Module 4. Integumentary (Dissection)Topic: Thin skin and subcutaneous tissues View: Layers
1
2 31
2 3
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Layers of Skin
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Epidermis Keratinized stratified
squamous epithelium ofvariable thickness
Avascular
Thick skinhas fivelayers (superficial todeep):
1. Stratum corneum2. Stratum lucidum
3. Stratum granulosum
4. Stratum spinosum
5. Stratum basale
Thin skinhas four layers(stratum lucidum ismissing)
Cells of stratum lucidumand stratum corneum lacknuclei
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Thick Skin High Magnification
SC = Stratum Corneum
SL = Stratum Lucidum
SG = Stratum GranulosumSS = Stratum Spinosum
SB = Stratum Basale
P = Papillary Layer of Dermis
SC
SL
SS
PP
SG
SB
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Thin Skin High Magnification
SC = Stratum CorneumSG = Stratum Granulosum
SS = Stratum Spinosum
SB = Stratum Basale
SC
SB
SSSG
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Stratum Corneum
Description:
Outermost layer of epidermis Up to 30 layers of cornified, dead cells
Dead cells contain keratin
Functions:
Creates barrier to fluids = waterproofing
Protection from abrasion and penetration, wear
and drying
Rendering the body relatively insensitive to
biological, chemical, and physical assaults
Cells sloughed (shed) from surface and continually
replaced from deeper layers
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In epidermis, between stratumgranulosum and stratum corneum
Present onlyin skin of palm (hand)and sole (foot) = THICK SKIN
Description:
Thin translucent layer composed of three
to five layers of keratinocytes withoutnuclei or organelles (clear layer)
Stratum Lucidum
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Above this layer, the capillaries in the
dermis can not supply the cells resulting
in cell death
Description:
Three to five layers of flattened
keratinocytes
Keratinocytes contain dark staining
keratohyalin granules (precursor of keratin)
Keratohyalin granules release a protein that binds
keratin filaments together into coarse, tough
bundles
Nuclei of keratinocytes in various stages of
degeneration
Stratum Granulosum
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Histological fixatives shrink keratinocytes so theypull away from each other; they remain attached
at desmosomes giving shrunken cells appearance
of porcupines attached to their neighbors = spiny
cells
Description:
Many layers of keratinocytes
Deepest cells can divide
Cells firmly attached to each other by
desmosomes (cell junctions)
Stratum Spinosum
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Deepest layer of epidermis firmly attached to dermis
Description:
Single layer of columnar or high cuboidal cells
resting on basement membrane
Keratinocyte is predominant cell
Also contains melanocytes, and stem cells
Skin color - the more active the melanocytesthe darker the skin
Stem cells produce keratinocytes and melanocytesvia mitosis.
All new epidermal cells are formed in this layer!!!
Stratum Basale (Basal Layer)
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Cells of Epidermis
Keratinocytes: Most abundant cell type in epidermis (90% of cells)
Produce keratin and arise from stratum basale every 20-45 days
Melanocytes:
Produce melanin pigment
Have long, branching cytoplasmic processes and are scattered among the keratinocytes within
stratum basale
Processes continually shed melanin-containing fragments from their tips
Keratinocytes phagocytize these fragments and accumulate melanin granules on the sunny
side of the nucleus. This shields the DNA within the nucleus from UV radiation.
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Dermis
Second major skin regioncontaining strong, flexibleconnective tissue
Composed of two layers
1. Papillary layercomposed of areolar(loose) connectivetissue
2. Reticular layercomposed of dense
irregular connectivetissue
Papillary
Layer
Reticular
Layer
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Relationship between epidermis and dermis
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Thick Skin Low Magnification
R = Reticular Layer of dermis
P = Papillary Layer of dermis
Epidermis
Dermis
R
P P
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Papillary Layer (Dermal Papilla)
Location:
Interface between dermis andepidermis
Description: Projection of papillary (external)
layer of dermis
Forms core of epidermal ridge Numerous and often branched
Contains capillary loops
Function: Provides nourishment to avascular
epidermis
APR 3.0 Module 4. Integumentary (Histology)
Topic: Thick skin View: LM: Low Magnification
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Reticular Layer Deep layer of dermis composed of
dense irregular connective tissue
Dense concentration of collagen and
elastin gives skin strength
Elastic fibers provide stretch-recoil
properties
Cleavage lines in this layer produce the
visible lines in our skin (Langers lines)
Cuts heal faster when the incision is
made parallel
Flexure lines create the folds in our
skin. Tears in this layer lead to stretch marks
APR 3.0 Module 4. Integumentary (Histology)
Topic: Thick skin View: LM: Low Magnification
Reticular Layer
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Hypodermis (Subcutaneous layer)
Not a part of the skin, but connectsskin to the muscles which liebeneath
Composed of areolar (loose)connective tissue and adipose tissue
Functions: Absorbs shock
Prevents heat loss from body;insulates the deep bodystructures
Common site of drug injectionbecause extensive vascularnetwork allows for rapidabsorption
Sub Q
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Summary of Skin Layers
f h k
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Burns of the Skin Partial-Thickness
First-degree Only the epidermis is damaged
Symptoms include localizedredness, swelling, and pain
Heals in 2 3 days = sunburn
Second-degree Epidermis and upper regions of
dermis are damaged
Symptoms mimic first degreeburns, but BLISTERS alsoappear; healing in 3 4 weeks
Full-Thickness = Third-degree
Entire thickness of the skin is
damaged
Burned area appears gray-white,cherry red, or black;
There is no initial edema or pain
(since nerve endings are destroyed)
Heals from the edges inward
Fluid loss is great, grafting often
necessary in larger burns
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Rule of Nines
Estimates the severity of burns
Burns considered critical if:
Over 25% of the body has second-degree
burns
Over 10% of the body has third-degree
burns
There are third-degree burns on face,
hands, or feet
Different areas of the body are calculated
as specific percentages (see figure)
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Appendages of the Skin
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Sweat Glands Different types prevent overheating of the body, secrete cerumen, and secrete
milk
Eccrine/Merocrine sweat glands found in palms, soles of the feet, andforehead. This sweat is water-like
Apocrine sweat glands found in axillary and genital areas. This sweatcontains fat and protein leading to body odor
Ceruminous glands modified apocrine glands in external ear canal thatsecrete cerumen (ear wax)
Mammary glands specialized apocrine glands that secrete milk.
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Merocrine Sweat Gland Low Magnification
SwG = Sweat Gland
SD = Sweat Gland Duct
SD
SwG
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Sebaceous Glands
Simple alveolar (holocrine) -secrete sebum (oil)
Most commonly found on face,
neck and trunk
Not present on palms or soles
Function - softens and lubricates
hair & skin bactericidal
Controlled by hormones
androgens; become activeduring puberty
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Sebaceous Gland Low Magnification
AP = Arrector Pili
SeG = Sebaceous Gland
AP
AP
AP
SeG
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Summary of Glands of Skin
H i & H i F lli l
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Hair & Hair Follicle Shaft = superficial portion of hair; above epidermis
Root sheathextending from the epidermal surface into the dermis (epidermal cells)
Deep end is expanded forming a hair bulb (location of active production of hair)
Hair Papilla= indentation of hair bulb containing blood vessels A knot of sensory nerve endings (a root hairplexus) wraps around each hair bulb Bending a hair stimulates these endings, hence our hairs act as sensitive touch receptors
Arrector pili- bundle of smooth muscle cells, makes hair stand on end, goose bumps, fear,insulation purposes, sympathetic nervous system
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Hair Follicle Medium Magnification
H = Hair
HB = Hair Bulb
HB
H
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Summary of Hair
S R i Ski
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Sensory Receptors in Skin Meissners (Tactile)corpuscle - superficial part of dermis (dermal papillae); touch,
tickle
Pacinian (Lamellated) corpuscle - larger and deeper in dermis/hypodermis; pressure Bare nerve endings (Afferent nerve endings)- pain sensation, heat and cold are also
perceived here.
ki d l i b
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Skin Model in Lab - KeyE = Epidermis
D = Dermis
H = HypodermisSeG = Sebaceous Gland
AP = Arrector Pili
HF = Hair Follicle
A = Adipose
SB = Stratum BasaleSD = Sweat Gland Duct
SwG = Sweat Gland
BV = Blood Vessels
HP = Hair Papilla
HB = Hair BulbSC = Stratum Corneum
M= Meissners Corpuscle
P = Pacinian Corpuscle
This model ill be part of P1