Transcript Tissue Level of Organization

Accessory Structures of Skin
Epidermal derivatives
Cells sink inward
during development to
form:
– hair
– oil glands
– sweat glands
– nails
Fig. 5.1
1
Structure & Fxn. of Hair
Shaft -- visible
– medulla, cortex &
cuticle
– straight hair  Xsec round
– wavy hair  X-sec
oval
– curly hair  x-sec
kidney shaped
Root -- below the
surface
Fig. 5.5
Follicle surrounds root
– external root
sheath
– internal root sheath
– base of follicle is
bulb
blood vessels
germinal cell
layer
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Hair Growth
Growth cycle = growth
stage & resting stage
Growth stage
– lasts 2 - 6 yrs.
– matrix cells @ base of
hair root produce
length
Resting stage
– lasts 3 mths.
– matrix cells inactive &
follicle atrophies
Old hair falls out as growth
stage begins again
– normal hair loss = 70 100 hairs/day
3
Hair Related Structures
Arrector pili
muscle
– smooth
muscle in
dermis
contracts w/
cold or fear.
– forms
goosebumps
as hair is
pulled
vertically
Hair root plexus
– detect hair
movement
Fig. 5.5
4
Glands of the Skin
Specialized exocrine
glands found in
dermis
Sebaceous (oil)
Sudiferous (sweat)
Ceruminous (wax)
Mammary (milk)
Fig. 5.1
5
Sebaceous (oil) glands
Fig. 5.6
Secretory portion in the
dermis
Most open onto hair shafts
Sebum
– Comb. of
cholesterol,
proteins, fats &
salts
– keeps hair & skin
soft & pliable
– inhibits growth of
bacteria & fungi
(ringworm)
Acne
– bacterial
inflammation of
glands
– secretions
stimulated by
hormones @
puberty
6
Sudoriferous (sweat) glands
Fig. 5.6
Eccrine (sweat)
glands
– most areas of
skin
– secretory portion
in dermis with
duct to surface
– regulate body
temperature
– H2O, NaCl,
urea, uric acid,
A.A., glucose, &
lactic acid
Apocrine (sweat) glands
– Armpit & pubic regions
– Also around areolae & bearded regions of adult males
– Secretory portion in dermis w/ duct that opens onto hair follicle
– Secretions more viscous & milky (lipids & protein)
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Ceruminous glands
Fig. 22.10
Modified sweat glands produce
waxy secretion in ear canal
Cerumin contains secretions of
oil & wax glands
Helps form barrier for entrance
of foreign bodies
Impacted cerumen may reduce
hearing
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Structure of Nails
Fig. 5.7
Tightly packed keratinized cells
Nail body
– visible portion pink due to
underlying capillaries
– free edge appears white
Nail root
– buried under skin layers
– lunula is white due to
thickened stratum basale
Eponychium (cuticle)
– stratum corneum layer
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Thin Skin vs. Thick Skin
Thick skin
– only on palms and soles
– thick epidermis (.6 to 4.5
mm.) with distinct
stratum lucidum & thick
stratum corneum
– lacks hair follicles and
sebaceous glands
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Thin Skin vs. Thick Skin
Thin skin
– covers most of body
– thin epidermis (.1 to .15 mm.)
that lacks stratum lucidum
– lacks epidermal ridges, has
fewer sweat glands & sensory
receptors
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Photodamage
UVA & UVB light can
damage skin
Acute overexposure
causes sunburn
UVA produces
oxygen free radicals
that damage collagen
& elastic fibers 
leads to wrinkling
DNA damage in
epidermal cells can
lead to skin cancer
12
Skin Cancer
1 million cases diagnosed per
year
3 common forms of skin
cancer
– basal cell carcinoma
(rarely metastasize)
– squamous cell carcinoma
(may metastasize)
– malignant melanomas
(metastasize rapidly)
most common cancer in
young women
arise from melanocytes
----life threatening
key to treatment is early
detection watch for
changes in symmetry,
border, color and size
risks factors include-skin color, sun
exposure, family
history, age &
immunological status
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Epidermal Wound Healing
Abrasion or minor burn
Basal cells migrate across the wound
Contact inhibition w/ other cells stops migration
Epidermal growth factor stimulates cell division
Full thickness of epidermis results from further cell division
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Deep Wound Healing
4 phases:
– Inflammatory
– Migratory
– Proliferative
– Maturation
Scar formation
– Hypertrophic
– Keloid
Which phases
have been left out
of this
illustration?
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Burns
Types of burns:
– 1st
– 2nd
– 3rd
Destruction of
proteins of the skin
– chemicals,
electricity, heat
Problems that result
– shock due to water, plasma & plasma
protein loss
– circulatory & kidney problems from
loss of plasma
– bacterial infection
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Skin Grafts
New skin can not regenerate if
stratum basale and its stem cells
are destroyed
Skin graft is covering of wound
with piece of healthy skin
To ensure no tissue rejection
occurs transplantations are:
– Autografts (from self)
– Isografts (from twin)
– Autologous skin used
transplantation of patients
skin grown in culture
http://www.nlm.nih.gov/medlineplus/ency/article/0
02982.htm  for more info.
Serial documentation of healing skin grafts
following burns in an 18 month old child.
Photographer: Gigi William's
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Pressure Sores
Decubitus ulcers
Caused by constant deficiency
of blood flow to tissue
Areas affected is skin over
bony prominence in bedridden
patients
Preventable w/ proper care
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