SKIN
Cutaneous membrane
Integumentary system
INTEGUMENTARY SYSTEM
Means “covering”
 Consists of Skin, sweat glands, oil glands,
hairs and nails

SKIN

Basic Functions

The skin protects deeper tissues from
– To protect
– To insulate
– To cushion
–
–
–
–
–
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Mechanical damage
Chemical damage
Bacterial damage
Ultraviolet radiation (damaging effects of sunlight)
Thermal (heat or cold) damage
Desiccation (drying out)
Aids in body heat loss or heat retention (controlled
by the nervous system)
 Aids in excretion of urea and uric acid
 Synthesizes vitamin D

STRUCTURE OF THE SKIN
2 kinds of tissue
1
EPIDERMIS- (stratified squamous)
KERATINOCYTES – cells which produce
KERATIN- fibrous protein that makes the
skin become hard and tough
2
DERMIS- dense connective tissue
firmly connected to epidermis, but can
separate and form a blister-
STRUCTURE OF THE SKIN

SUBCUTANEOUS
TISSUE
(HYPODERMIS)- not
considered skinadipose tissue that
anchors skin to
surrounding organs
EPIDERMIS

5 LAYERS CALLED STRATA- all layers are
avascular- has no blood supply
EPIDERMIS

STRATUM BASALE- single bottom layer
of epidermis- columnar in shape- receive
the most nourishment-constantly
undergoing cell division with all the new
daughter cells pushed upwards
EPIDERMIS

STRATUM SPINOSUM-spiny layer of
cuboidal cells- nuclei appear dark- first
signs of cell death
EPIDERMIS

STRATUM
GRANULOSUMpartially flattened
cells whose
cytoplasm contains
small granular
proteins that are in
the process of
turning into keratinnucleus begins to
disappear
EPIDERMIS

–
STRATUM LUCIDUM
– clear layer- 3 to 4
rows of cells that
are flattened and
now dead- keratin
formation continues
is only where the
skin is hairless and
extra thick, palm
of the hands and
soles of the feet
EPIDERMIS

STRATUM CORNEUM-most superficial
layer- 20-50 cells thick accounts for
75% of the skins thickness

slowly rubs and flakes off and is
replaced by cells produced by the
division of the deeper stratum basale
cells. Every 25 to 45 days we have a
“new” epidermis.
KERATINOCYTES
 Keratin
is found the stratum
corneum and is a tough protein that
provides a durable “overcoat” for
the body, protecting the deeper
cells from the hostile external
environment. It also protects them
from water loss and helps the body
resist biological, chemical, and
physical assault
MELANOCYTES

Melanin is a pigment that ranges in color
from yellow to brown to black and is
mainly found in the stratum basale.
Sunlight stimulates the melanocytes to
produce melanin, tanning occurs. The
stratum basale cells phagocytize the
pigment, accumulating it within them.
The melanin forms a protective pigment
“umbrella” over the nuclei that shields
their genetic material from the
damaging effects UV RAYS. Freckles
and moles are seen where melanin is
concentrated in one spot
DERMIS
The dermis is a strong, stretchy envelope that helps
to hold the body together
Contains collagen and elastic fibers
Collagen- provides toughness, also attracts and binds to
water to keep skin hydrated
Elastic- provides elasticity
 It varies in thickness, thick on the palms of the hand
and soles of the feet, but quite thin on the eye lids
 Consists of two regions
1. PAPILLARY LAYER- upper region
2. RETICULAR LAYER- lower region

DERMIS
PAPILLARY LAYER – (upper)-contains
dermal papillae

DERMAL PAPILLAE- uneven fingerlike
projections from its superior surface
(fingerprints)- these projections can house
many things
 Capillary Loops Free nerve endings (pain receptors)
 Meissner’s corpuscles- (touch receptors)
DERMIS
DERMAL PAPILLAE can house many
things
1. Capillary Loops- which can increase /
decrease blood flow to skin
2. Free nerve endings (pain receptors)
some receptors detect hot or cold.
3. Meissner’s corpuscles- (touch
receptors)
DERMIS
RETICULAR LAYER – (deep)Contains
1. BLOOD VESSELS
2. SUDORIFEROUS GLANDS(sweat) (2 types)
3. SEBACEOUS GLANDS(oil)
4. PACINIAN CORPUSCLESdeep pressure receptors

SUDORIFEROUS GLANDSTwo types
1. ECCRINE GLANDS more numerous and
produce sweatSWEAT – contains
1.
water
2.
sodium chloride
3.
vitamin C
4.
metabolic waste
(ammonia, urea)
5.
lactic acid (attracts
mosquitos)
SUDORIFEROUS GLANDS-
FUNCTIONS OF SWEAT
1.
2.
Evaporation of sweat off the skins
surface gives cooling effect
Acidic (pH of 4-6) inhibits bacteria
growth
SUDORIFEROUS GLANDS2.
APOCRINE GLANDS- found only in the
armpit and genital areas
SECRETION contains fatty acids and
proteins (yellowish or milky color)
The secretion is odorless but bacteria
can grow from it giving off an unpleasant
odor.
SEBACEOUS GLANDS (oil glands)
Typically located near hair follicle and dump
secretions (SEBUM) there.
SEBUM- lubricant that keeps skin soft and
moist. Keeps hair from becoming brittle.
Also contains chemicals to kill bacteria.
SEBACEOUS GLANDS (oil glands)
If a sebaceous gland becomes blocked a
WHITEHEAD APPEARS
If that material oxidizes and dries then a
BLACKHEAD FORMS
SKIN COLOR
3 pigments contribute
1. MELANIN in the epidermis (amounts and types)
2. CAROTENE- (orange-yellow pigment found in
carrots)- found in the stratum corneum and
subcutaneous tissue
3. Amount of OXYGEN bound to hemoglobin of Red
blood Cells- when poorly oxygenated skin
appear blue called CYANOSIS

HAIR

Is a flexible outgrowth of dead (KERATINIZED)
epithelial cells
In earlier humans hair provided insulation in cold
weather
It has a few minor protective functions

Has 3 layers


– Guarding the head against bumps
– Shields the eye (eyelashes)
– Helps to keep foreign particles out of the respiratory
tract (nose hairs)
– Medulla~inner most
– Cortex~middle bulky area
– Cuticle~outermost, single layer
LAYERS OF HAIR

The MEDULLA is a honeycomb structure of
keratin and air spaces
LAYERS OF HAIR

The CORTEX gives flexibility and tensile strength
to hair and contains melanin (giving hair its
color). Without melanin, the partly hollow hair
appears grey.
LAYERS OF HAIR

The CUTICLE is made from 6 to 11 layers of overlapping
semi-transparent scales (which make the hair waterproof
and allow it to be stretched). Someone with thick, course
hair will have more overlapping layers of cuticles that
someone with fine hair.
HAIR
Shaft is the part exposed above the skin
Root is the part below the surface surrounded by the
hair follicle
Arrector Pilli Muscles are the smooth muscle cells
which are attached to dermal tissue and follicle which
can contract and produce “goose bumps”. It’s purpose
is to keep warm. (Hair follicles are always at an angle
and the arrector pilli muscles reduce that angle)
Hair Bulb Matrix is the area at the (inferior) end of
the root where cell stratum basale epithelial cells
rapidly divides promoting hair growth (1 mm every 3
days)
Melanocytes are located in the stratum basale layer
which give your hair its color
HAIR
HAIR BULB MATRIX (growth zone)
Consists of:
1. PAPILLA- well vascularized connective
tissue that goes up into the hair bulb
2. STRATUM BASALE- one layer of cells
around Papilla- where hair growth occurs
HAIR BULB MATRIX
Nails
A scalelike modification of the epidermis
that corresponds to hoofs or claws
 Nearly colorless except they look pink due to
rich blood supply in the dermis beneath

 Three
parts of the nail
1. Body~area that is visible
2. Free Edge~area that overhangs
the digit
3. Root~area covered by nail folds,
embedded in the skin
Nails
Nail Folds are
the overlapping
skin of the nail
CUTICLE is the
thick proximal
nail fold
Nails
 Nail
Matrix is the
area responsible
for nail growth
 As the nail cells are
produced by the
matrix, they
become heavily
keratinized and die
BURNS

BURN- tissue damage and cell death caused by
intense heat, electricity, UV radiation, or
chemicals
2 LIFE THREATENING PROBLEMS RESULT
1. Loss of fluids- ( proteins and electrolytes)
Leads to dehydration, circulatory shock, kidney
shutdown
2. Infection - bacteria or fungi infecting deeper
unprotected tissues
SEVERITY OF BURNS

FIRST DEGREE BURNS- only epidermis is
damaged- temporary discomfort. (most
sunburns)
SEVERITY OF BURNS

SECOND DEGREE BURNS- injury to
epidermis and upper region of dermisBlisters will appear- but skin will
regenerate
THIRD DEGREE BURNS
Third degree burns destroy all three layers of the
skin. Regeneration of the skin is impossible
because blood vessels have been destroyed.
The good news is that Nerve endings have also
been destroyed. NO PAIN!!! YEAH!
THIRD DEGREE BURNS

Burned areas appear
gray-white or
blackened

Skin transplants are
necessary
SKIN CANCER
-Skin Cancer is the single most common
cancer in humans.
 -Although most skin tumors are benign
and to not spread to other body organs,
some can be malignant or cancerous.
 -Single biggest risk factor is overexposure
to the sun
 - Other risk factors include skin infections,
chemicals, or physical trauma

BASAL CELL CARCINOMAmost common and least malignant type of skin
cancer.
 Stratum Basale cells are altered to where they
no longer distinguish the boundary of epidermis
and dermis. New dividing cells are pushed in all
directions including into the dermis and
subcutaneous layers.
 - appears as a dome shaped nodule that
develops a central ulcer with a pearly beaded
edge
 - 99% curable if cancer is surgically removed.

SQUAMOUS CELL CARCINOMAarises from the stratum spinosum
 - appears as a small rounded elevation
that is red and scaly which gradually forms
a shallow ulcer with a firm raised border
 - appears most often on the scalp, ears,
back of the hand, and lower lip.
 - can become malignant and invade
adjacent lymph nodes if not removed.

MALIGNANT MELANOMAcancer of the melanocytes- occurs
wherever there are pigment.
 - accounts for only 5% of cancers
 - develop spontaneously or from
pigmented moles
 -rapidly spread and attack surrounding
lymph and blood vessels
 -chance for survival 50%

When should you worry about a
mole being cancerous?
FOLLOW THE ABCD RULE (pg 111) Asymmetry,
 Border irregularity (lesion is not smooth
but has indentions),
 Color (blacks, browns, tans, blues and
reds)
 Diameter (more than 6 mm)

BURNS- RULES OF 9

RULE of NINES- body is divided into 11
areas that each account for 9 %

Example- 4.5 % front of arm, 4.5 % back
of arm, front of leg 9%, back of leg 9%
BURNS
Burns are considered critical if:
1. Over 25 % of the body has second
degree burns
2. Over 10 % of the body has third degree
burn
3. There are third degree burns of the face,
hands, or feet

How does the skin react to Heat
or cold?
HEAT
 1. Nerves in dermal papillae send signals
to brain (hypothalamus) of temp. change
 2. Capillaries are opened up completely to
allow blood to RADIATE out heat
 3. ECCRINE GLANDS are activated to
allow sweat evaporation to cool the body.

If body gets too HOT
HEAT EXHAUSTION or HEAT STROKE can
occur
How does the skin react to Heat
or cold?
COLD
1. Nerves in dermal papillae send signals to brain
(hypothalamus) of temp. change
2. VASOCONSTRICTION of blood vessels and vascular
shunts redirect blood away from the capillaries (surface)
3. Keeps blood near the core for warmth
4. ARRECTOR PILI MUSCLES – contract to form an extra
layer of insulation
5. If body temperature is still too low the SHIVERING
occurs to produce more heat.
If the body gets too cold

FROSTBITE or HYPOTHERMIA can set in .
The AGING of SKIN
As Adults get older1. Amount of SUBCUTANEOUS TISSUE decreases
(less insulation)
2. Amount of OIL decreases (drier, itchier)
3. Layers of skin become thinner
4. Loss of collagen and elastin fibers
More susceptible to cold, bruising, and other types
of injuries
Other problems with aging skin
Loss of elasticity and subcutaneous tissue
causes skin to SAG (Example- bags under the
eyes, jowls begin to sag)
MAJOR CAUSES- exposure to sun, dehydration,
poor nutrition, poor sleeping habits
1.
Loss of hair follicles-- ALOPECIA- “thinning of
the hair”
3. MALE PATTERN BALDNESS- caused by loss of
testosterone
2.