functions of skin

1. The Integumentary System
Ya gotta have skin to keep your
insides in!!!
Chapter 5 pages 142-159

2. Skin Factoids
Skin is part of the
Integumentary System.
-Largest organ of the body.
(21.5 ft2)( 12-15% of
body weight).
-Thickness varies:
.5 cm on upper back
.05 cm on eyelids
Hair and sweat glands are
not located in all areas!
- No hair on the palms
- No sweat glands on
the eye lids.

3. Skin Trivia
Skin is always being
replaced from
within.
Most of the dust in
your house is
dead skin.
By the time you are
70 you will have
shed 70 lbs. of
skin.
• Skin is important
in helping the
body to maintain
homeostasis
(“steady state) of
such things as
body
temperature, fluid
balance and

10. General Skin
Structure
• 2 main layers - epidermis
and dermis
• Epidermis
• 4 to 5 layers of epithelium
• 3 main cell types
– Keratinocytes
– Melanocytes
– Langerhans cells
(like the one
pictured here) are
free ranging white
blood cells that are
found in the stratum
spinosum. They
phagocytize foreign
material and bacteria.

11. The skin as an ecosystem
• The skin supports a wide variety
of microorganisms.
• Species of Bacteria and yeasts
inhabit the surface of the skin
and help to protect us from more
dangerous microbes.
• We are all hosts of tiny mites
which feed on our dead skin.
• They are most common in the
eyebrows and eyelashes.
• All houses have dust mites that
eat the dead skin that
accumulates in pillows and
cushions.
• These mites can become very
numerous and some people can
become allergic to their
droppings.
• It is suspected that this may be
the explanation for some cases
of asthma.

12. This picture shows a group of follicle mites nested in the
follicle of an eyebrow.

13. Dust Mite

14. Perspiration
• Inactive person (3 mL/hr)
• Active person (1 L/ hr) In hot
climates this can increase to 2
to 3 L/hr in 6 weeks.
• In addition to cooling the body
sweat provides nutrients for
certain bacteria and fungi that
lie on the skins surface.
• These bacteria produce lactic
acid which prevents many kinds
of harmful bacteria from
growing on the skin!
• Sweat is produced in the sweat
glands and exits through the
sweat pore.
• It is mostly water. There is
some urea, salts, proteins and
oils that are also secreted.

15. Sweat Gland, cross section (430X)

16. Sebaceous gland
Secreting oil to help lubricate and protect the hair shaft.

17. Apocrine glands
Apocrine sweat glands are formed
from the same structure as the
hair follicle and sebaceous
glands.
• They produce a thicker, viscous
liquid that produces a noticeable
odor.
• The apocrine glands become
very active with the onset of
puberty. They are found in the
armpit and the genital area.
• The milk glands in the breasts are
modified apocrine sweat glands.
• Body odor is produced by micro-
organisms that grow where the
apocrine glands exist.
• The bacteria produce an odor as
they digest this sebum.
• Since they can only do this if
water is present many deodorants
are antiperspirants as well.

19. Functions of Skin
• The skin provides
protection against
mechanical injury.
• The skin helps to
prevent the penetration
of many kinds of
harmful chemicals.
• This photograph shows
a typical case of poison
ivy. Poison ivy is
caused by an allergic
reaction between the
body and an oil,
urushiol, that is
produced by this plant.
• 85% of the people in
the US are sensitive to
this oil.

20. Functions of Skin
• The skin, with its
continuous waterproof
covering, helps to prevent
microbes from getting
inside the body.
• The skin is host to a
community of microbes
that assists in the
prevention of disease.

21. Functions of Skin
• Prevention of
dehydration. For burn
patients who lose
more than 50% of
their skin, they are
very likely to become
severely dehydrated.
• The skin provides
protection of the
internal sea that
bathes all of our cells.
• This picture is of
human skin magnified
1000X by a scanning
electron microscope.

22. Functions of Skin
• The skin helps
to maintain a
constant body
temperature.
• Extensive
capillary
networks and
sweat glands
help to radiate
excess heat and
to cool the
body through
evaporation of
water.

23. Functions of Skin
• Excretion of
Wastes.
• Water, urea and
some salt are
excreted when
people sweat.
• Recently people
discovered a new
compound in sweat,
a protein called
dermicidin.
• This protein seems
to play a role in
inhibiting bacterial
growth.

24. Functions of Skin
• The skin serves as a large
sensory receptor organ of
the body.
• Many nerve endings end in
the skin.
• Sensations include touch,
pressure, heat, cold, and
pain.
• Meissner’s corpuscle (fine
touch),
• free nerve endings (touch,
pressure and pain, (tickle?).
• Merkel’s discs (light touch
and pressure),
• Krause’s end bulbs (cold?),
• Pacinian corpuscle (heavy
pressure and vibration)

26. Skin nerve receptors
• Pacinian corpuscle
• Sensitive to heavy
pressure and
vibration
• Abundant near
joints and skeletal
muscles, palms
and soles

27. • Meissner’s corpuscle
• Fine touch receptors
• Found in high concentrations in fingertips
• Important in two point discrimination

28. Skin nerve receptors
• Pain, cold and
warmth nerve
receptors are free
nerve endings
located very close
to the epidemis
• Cornea of the eye
contains only these
nerve receptors

29. Cold and Warmth
• Detected by specific free dendrites
• 3 to 10 times more cold than warm receptors
• Extremes in temp. (<100 C and >450C) involve pain receptors

30. Functions of Skin
• Vitamin D
synthesis
• Skin that is
exposed to the sun
will produce
Vitamin D.
• Vitamin D seems to
play a role in
preventing certain
types of cancer.

31. Hair Structure and function
• Hair protects the
head, eyes and
ears.
• For creatures in
cold climates
often there are
two layers.
• Most hair
structure is the
same.
• Hair grows at
different rates.

32. Hair continued
• Composed of
keratin
• Grows in cycles
• Grows faster in the
morning than the
evening.
• Curly hair is oval in
shape
• Grey hair lacks
pigment

33. Hair Transplants
• The first step in the hair
transplant process is the
design of the hairline.
• Next the donor area is
prepared.
• Hair in the back is lifted
and a narrow strip of hair
is trimmed to about
1/16th of an inch.

34. Hair Transplant
Procedure
• Both the top and the back of
the scalp are then
anesthetized.
• Patients are given the option
for nitrous oxide (laughing
gas) while the local
anesthesia is applied.
• Narrow strips of hair bearing
skin are removed from the
donor area and the hair from
above and below is then
brought back together with a
running stitch.
• The stitches are covered by
your hair and removed in ten
days, usually leaving a thin
scar line that is concealed by
your own hair.

35. Hair Transplant procedure
• From the donor strip tiny grafts are prepared.
• Grafts for the hairline are usually between 1 to 3 hairs and are dissected
under a microscope to preserve every follicle possible.

36. Hair Transplant
procedure
• The hair transplant
surgeon next creates
the sites where the
grafts will be placed.
• Tiny slit incisions are
made at the hairline
for the smallest single
hair grafts.

37. Hair Transplants cont.
• As the surgeon works back he will
make gradually larger slit and slot
incisions (approximately 1/32" wide
by 1/8" long) .
• After the procedure most patients
are given a baseball cap or bandana.
• There is usually no bandage and the
hair can be washed in two days.
• Tiny crusts will form where the
transplants have been placed and
usually shed in 4 to 7 days.
• The small hairs in the newly
transplanted grafts normally shed
within 2 to 4 weeks after the
procedure.
• Permanent hair growth usually
begins in 8 to 12 weeks. Significant
hair growth within 6 to 8 months
and full hair growth within 9 to 12
months.

38. Nails
• Horny plates
composed of keratin
• Growth occurs in nail
matrix.
• Cells grow and fill
with keratin
• .1 mm/day average
growth rate

39. African Black Rhinoceros
• The horns of the
Black Rhinoceros
is made up of the
same protein as
found in your nails
and the stratum
corneum.
• The Black
Rhinoceros’ thick
skin is really a very
thick layer of
keratin filled cells.

40. Skin pigmentation
• Oxyhemoglobin,
carotene and melanin
determine skin color
• Melanin produced by
melanocytes in
stratum basale.
• Melanocytes thought
to originate from
nervous tissue.
• Melanin produced in
reaction to UV
radiation.

41. Burns
• Classified by degree
• 1st degree - redness,
swelling
• 2nd degree - blisters
• 3rd degree - destroyed
skin tissue.
• 2nd and 3rd degree
burns need medical
attention.
• Burns to the head, neck
and groin are the most
serious.
• When the skin is
burned, it can’t protect
the body against
bacteria, prevent the
loss of body fluid, or
keep the body at a
normal temperature.
• 2nd and/or 3rd degree
burns over 30% of the
body are usually fatal.

43. Burn Care
• The patient is placed in a
special cart that allows for
cleansing of the burned area.
• Cleansing is initially done
with soap and water.
• Medication is given to relieve
pain and antibiotics and
bandages are used.
• Surgery is performed to
remove dead and dying tissue.
(debridement)
• Skin grafting is done using
skin from healthy areas of the
patient.
• If the area burned is large it
may be necessary to do more
than one grafting operation.

44. Skin Grafting
• Dead skin is removed from
the damaged area
(debridement)
• A section of skin larger than
the injury is placed over the
burn and covered with
bulky, wet bandages that
have been soaked in an
antibiotic.
• The graft begins to grow
and adhere in 48 hours and
usually is totally attached in
4 to 5 days.
• The patient will need to
protect this area for up to
two weeks before it is
totally healed

45. Artificial Skin
• The typical cover for extensive
burn wounds was cadaver skin,
known as allografts.
• The skin grafts did not always
have the desired effects. They
sometimes introduce disease to
the burn victim or were rejected
by the body.
• In the 1980’s artificial skin was
successfully developed.
• Fibroblasts from neonatal foreskin
samples are enmeshed in a
collagen gel.
• After several weeks keratinocytes
are added and they form an
epidermal layer.

46. Artificial Skin
• An artificial skin graft
eliminates the need for tissue
typing.
• Artificial skin can be made in
large quantities and frozen for
storage and shipping, making
it available as needed.
• Each culture is screened for
pathogens, reducing the
chance of infection.
• Because artificial skin does
not contain immunogenic cells
such as dendritic cells and
capillary endothelial cells, it is
not rejected by the body.
• Finally, rehabilitation time is
significantly reduced.

47. Skin Cancer
• 3 kinds basal, squamos
and melanoma
• Basal cell carcinoma
involves cells in the
stratum basale which
become cancerous
• Usually noticed as
persistant skin ulcers.
• metastasis is uncommon

48. Skin Cancer
• Squamous cell
carcinoma
• Begins in stratum
spinosum
• Metastasis may occur
so these growths are
operated on as soon as
they are diagnosed.

49. Skin Cancer
• Malignant Melanoma
is cause by cancerous
melanocytes
• Metastasis is common
and early treatment is
essential
• Increased 600% in last
15 years
• 6/7 of all skin cancers
• Most common cancer
in women aged 25-29.
• Often starts as a mole
that suddenly changes
in size and texture.

50. Wounds
• Injured cells release
histamine which
causes swelling and
dialation of blood
vessels.
• White blood cells
released from bone
marrow.
• Clot forms
• A decrease in chalones
causes increased cell
division.
• The drying scab helps
to pull the injured
layers together.
• Fibroblasts in the
dermis produce
collagen which fills in
the wound below the
scab.

51. Fingerprints
• Chinese first used
fingerprints thousands of
years ago as signatures
on documents.
• The formal name for
fingerprinting in
dactyloscopy.
• Fingerprints are caused
by the pattern of ridges
on the dermal papilla.
• They are also found in
monkeys, gorillas,
orangutans and some
kinds of birds as well as
humans.
• There are also toe
prints, palm prints,
soleprints (footprints)
and lip prints.
• 1893 Sir Frances
Galton proved that no
two prints were alike.
The following year the
first identification of a

52. The Henry System of Fingerprint
classification

53. Fingerprint residue
• Twins, triplets and
quadruplets all have different
prints.
• Fingerprints are composed
mostly of sweat or moisture
with tiny traces of urea,
proteins and sebum.
• Latent prints can be dusted
and lifted several months
after the impressions is made
and up to 10 years if a laser
is used.
• Fingerprints can not be
copied or forged.
• The F.B.I. identifies over
2.700 fugitives a month
through fingerprints, and
they have nearly 200 million
fingerprints on file.

54. Acne
• For reasons not
completely understood,
follicles or pores often
become blocked.
• Sebum (oil) which
normally drains to the
surface is trapped and
bacteria start growing.
• Both whiteheads and
blackheads start out as
microcomedones as the
one indicated in this
picture.
• Microcomedones
become comedones
which are either
whiteheads or blackheads

55. Trapped bacteria under the surface of the skin cause
a small infection in the area of the follicle

56. Blackheads occur when the trapped sebum and
bacteria partially open to the surface. They turn
black because of the skin pigment melanin.

57. Acne Treatments
• Acne is caused by the
bacterium (propionibacterium
acnes)
• This bacterium can be killed
by the compound benzoyl
peroxide. (pictured to the
right)
• Treatments can include
antibiotics, but the bacteria
can develop a tolerance for
antibiotics.
• Scrubbing and irritating the
skin can make matters worse.

58. Severe Acne
• Acne Rosacea - A
red rash
accompanied by
pimples and
blackheads. It can
cause swelling of
the nose and
growth of excess
tissue. This
condition needs
treatment from a
doctor.

59. Acne conglobata
• Acne Conglobata -
characterized by numerous
large leisons on the face
and body
• Nodules and hard
reddened lumps in the skin
are present.
• Cysts, large pustules with
a white or yellowish
center surrounded by a
reddish circle.
• Treated with antibiotics

60. Acne Fulminans
• An Abrupt onset of Acne
Conglobata that usually
affects young men in their
late teens and 20’s.
• Severe nodulocystic, often
ulcerating acne are
apparent.
• This affliction often
includes fever and aching
joints.
• It is treated with accutane
and steroids. Antibiotics
do not work well with this
disease.

61. Corns and Calluses (Hyperkeratosis)
• Structurally they are the same.
The skin has responded to
friction and pressure with
increased epidermal growth.
• Most of the time this is a natural
and beneficial response that
protects the skin and the tissues
underneath the skin.
• They tend to form on the foot and
the hands.
• Corns are the result of a callus
on the foot continuing to grow to
the point that it becomes painful.
They are a horny thickening of
the skin, dome shaped, with the
dome pointing down into the
skin.

62. Freckles
• Freckles are flat, circular spots that
typically are the size of the head of a
nail.
• The spots develop randomly on the
skin, especially after repeated
exposure to sunlight and particularly in
persons of fair complexion.
• Freckles vary in color -- they may be
red, yellow, tan, light-brown, brown, or
black -- but they are always darker than
the skin around them since they are
due to deposits of the dark pigment
called melanin.
• There are two types of freckles --
ephelides and lentigines:
• Ephelides (singular: ephelis, the Greek
word for freckle): This term refers to flat
spots that are red or light-brown and
typically appear during the sunny
months and fade in the winter.
• Lentigines (singular: lentigo, from the
Latin word for lentil): Children may
develop a small tan, brown, or black
spot which tends to be darker than an
ephelis-type freckle and which does not
fade in the winter.

63. Plantars Warts
• Plantars Warts are the most
common skin viral infection.
• The virus (human papilloma
virus (HPV))invades the skin
cells and causes them to grow
abnormally.
• People commonly get the virus
from public swimming pools or
showers.
• They occur mostly on the plantar
or the soles of the feet.
• They appear as raised, skin-
colored bumps with a rough
surface.
• The surface is made up of
dozens of tiny finger-like
projections.
• They vary in size from the tip of
a pencil to as big as a dime.
• In time the wart does go away.
• Many people will treat these
warts because of the pain they
can cause when walking or
running.
• After a while a person becomes
immune to these viruses.

64. Molluscum warts
• Molluscum contagiosum warts
These are another type of wart
caused by a different virus from
the classic wart.
• They have a different appearance
and usually occur on the chest,
abdomen, upper thighs, and
occasionally the face.
• They are skin-colored bumps, can
vary in size from the tip of a
ballpoint pen to about half the size
of the eraser end of a pencil, are
smooth surfaced, often have a
dimple in the center, and usually
occur in clusters.
• They can itch. They are more
contagious than classic warts, and
are transmitted by repeated close
physical contact with the warts.
• These often do not require any
treatment, and will go away on
their own usually within 1 year.
They are more difficult to treat
because there can be several
dozen at any time.

65. Keloids
• keloids extend beyond a
healed wound with clawlike
extensions.
• keloids may arise without
history of injury.
• more common in black
people than white people.
• earlobes, shoulders, upper
back, chest
• hypertrophic scars tend to
regress in time
• keloids may expand for
decades
• histology: densely packed,
bright pink collagen bundles
in a haphazard array;
increased number of
fibroblasts and blood vessels
in early lesions

66. Port Wine Stain
• vascular malformation
(not neoplasm) of dermal
blood vessels
• always present at birth
• never spontaneously
disappears
• macular in infancy;
become papular and
darker with age
• histology: increased
number of blood vessels,
with larger lumens, in
upper dermis

67. Albinism
• Albinism (from Latin albus, meaning
"white") is a lack of pigmentation in the eyes,
skin and hair.
• It is an inherited condition resulting from the
combination of recessive alleles passed from
both parents of an individual.
• This condition is known to affect mammals,
fish, birds, reptiles, and amphibians.
• While the most common term for an
individual affected by albinism is "albino",
some of them prefer "person with albinism",
because "albino" is often used in a derogatory
way.
• The gene which results in albinism prevents
the body from making the usual amounts of a
pigment called melanin.
• The lack of pigment in the skin leads to
increased incidence of burning and skin
cancer.
• The lack of pigment in the iris of the eyes
leads to increased incidence of the eyes to
light.
• People with albinism are not less healthy and
lead normal lives of normal length.

68. A girl with albinism and her mother.

69. Cat Skin cross section
• Same basic structure as
human skin.
• Tends to have a thicker
epidermis overall.
• The outer epidermis heals
quickly and can lock bacteria
inside the body creating
abscesses.
• Abscesses, if severe, may
need to be operated on to
remove the infection.
• In cat species that live in
colder weather there will be
an inner dense layer of fur as
in dogs.
• Note the lack of sweat glands.

70. Cat Skin cross section another view

71. Whale Blubber
• The outermost fat
layer,the blubber,
provides insulation for the
body; the thickness varies
from 5 to 50 centimetres,
depending on the
species.
• The limited transportation
of blood to the outer
layers of the body also
reduces heat loss.
• The
insulating capability of
whale blubber is
so effective, that the
temperature of a stranded
whale rises rapidly from
37 0 C to 50 - 60 0 C and
the carcass begins to

72. Sperm Whale
• The Sperm Whale is exceptional for its very
large head.
• In males the head is typically one-third of the
animal's length.
• In contrast to the smooth skin of most other
large whales, the skin on the back of the
Sperm Whale is usually knobbly and has been
likened to a prune by whale-watching
enthusiasts
• White albino whales have also been reported.
• The brain of the Sperm Whale is the largest
and heaviest known of any modern or extinct
animal (weighing on average 7 kg (15 lb) in a
grown male.
• They are the largest predator that has ever
lived.
• They are the only whale species to have
successfully sunk a ship (twice).
• They spend 80% of their lives underwater in
search of food.

73. Sperm Whales
• Sperm Whale size has decreased
dramatically.
• The largest males were killed first for they
had more spermaceti oil which was of
great value in the 18th and 19th century.
• In a Nantucket museum there is a jawbone
of a sperm whale which is 5.5 m (18 ft).
• The jawbone makes up to 20%-25% of the
sperm whale's overall body length.
• This whale might have been 28 m (90 ft)
long, with mass of around 75 tons.
• Another evidence of large bulls of the past
resides in New Bedford museum, a 17 ft
jaw of a bull that could have been about
84 feet) long, with a mass of about 60tons.
• In addition, log books found in the
Nantucket and Bedford museums are filled
with references to bulls that were,
considering the amount of oil they yielded,
about the same size as these two examples.

74. Sperm Whale Size cont.
• Today, Sperm Whale
males do not usually
exceed 18 m (60 ft) in
length and 50 tons.
• The largest sperm
whales observed are
comparable in size to
the fin whale (and
smaller than blue
whales), making the
sperm whale either the
second or third largest
animal species alive.

75. Nantucket Whaling Museum

76. Female Sperm Whale, Azores
• Females are seldom longer than 46 feet.
• They are much slimmer with weights never exceeding 20 tons.
• They live in large pods and are visited by mature bulls during the
breeding season.
• They are the slowest reproducing mammal on the planet, females
having a calf every 11 years.
• The wrinkly skin is thought to be a result of the animals incredibly