lecture 4 integumentary
TRANSCRIPT
8/3/2019 Lecture 4 Integumentary
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Would you be enticed by an
advertisement for a coat that is
waterproof, stretchable, washable,
and permanent-press, that invisibly
repairs small cuts, rips, and burns,
and that is guaranteed to last a life-time with reasonable care?
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INTEGUMENTARY
SYSTEM
formed by the skin, hair, nails, and
associated glands, and wraps the body.
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SKIN
As an organ, the skin is the largest and heaviest inthe body. In an average adult,
the skin covers about 21.5 square feet (2 square
meters) and accounts for approximately 7percent of body weight, or about 11 pounds (5kilograms) in a 160-pound (73-kilogram) person.
It ranges in thickness from 0.04 to 0.08 inches (1to 2 millimeters), but can measure up to 0.2inches (6 millimeters) thick on the palms of the
hands and the soles of the feet.
It is the most visible organ system and one of the mostcomplex.
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12 good reasons whythe integumentary
system is so importantto us!
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1.The skin is our first line
of defense against
disease.
It prevents externalcontamination from
entering our bodies and
helps to maintain the
sterility of our inner
body.
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2. It prevents excessive
amounts of water from
leaving the body.
Without skin, we would either
become soggy from absorbingwater while bathing or swimming
or shrivel up from the loss of
water to the air through
evaporation. In other words it
keeps moisture in and moisture
out--a perfect balance.
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3. It serves as a
protection to our bodies.
It acts as a cushion when we are
hit and bumped by our
environment. It takes a lot of
abuse such as from wood slivers,
mosquitos, thorns., and bees.
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4. It helps to regulate our
body temperature. It is a form of insulation to keep thebody heat in and the cold out. When thetemperature on the outside of the body
is hot the blood vessels within our
integumentary system become larger or dilate, excess heat from the blood
can escape through the skin. Thesweat glands also kick in and help rid
our bodies of excess heat byevaporation. When the body becomes
cold the blood vessels become smaller or constrict. This allows the bloodvessels to lay deeper within the
integumentary system and retain theheat, rather than losing it.
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5. It can change its
color to adapt.5. It becomes tan in order to
block the penetration of the
ultraviolet rays from the sunthat are so damaging to our
bodies. (However, frequent
tanning and spending time inthe sun without protection is
the major cause of skin cancers
and should be avoided.)
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6. It stores some
vitamins.
It reacts with the sunlight andmanufacture vitamin D.
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. ea s se y
automatically repairing
damage inflicted upon itsuch as cuts, scratches and
puncture wounds.
8.It grows specialized
hairs that help keep
foreign matter out of our eyes and nostrils.
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9. It reveals a lot about
us.
It allows others to
know that we areembarrassed or afraid
by displaying a red or
pale color, growing
goose pimples or
sweating.
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10.It keeps us in touch with
our environment throughspecial sensory receptors
built into our skin.
Our skin senses pain,
changes in temperature,different textures, pressureand touch.
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11. It makes me one
of a kind!The top layer of skin has ridges thatform patterns on our fingers, soles of
our feet and palms of our handswhere the skin is thick. No oneperson has an identical pattern toanother. Not even in twins! Each
print is unique. Some studies have
recently discovered that thepatterns of our "prints" are linked todisorders such as Down's syndrome.
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12.It helps the body to
eliminate wastes
Elimination occursthrough the pores in the
skin. This is a good
reason to frequently washand refreshen your skin.
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The Integumentary System: Words to
Know
Apocrine sweat glands (AP-oh-krin):
Sweat glands located primarily in the armpit andgenital areas.
Arrector pili muscle (ah-REK-tor PI-li): Smooth muscle attached to a hair follicle that,when stimulated, pulls on the follicle, causingthe hair shaft to stand upright.
Dermal papillae (DER-mal pah-PILL-ee):
Finger-like projections extending upward from
the dermis containing blood capillaries, whichprovide nutrients for the lower layer of theepidermis; also form the characteristic ridges onthe skin surface of the hands (fingerprints) andfeet.
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Dermis (DER-miss):
Thick, inner layer of the skin.
Eccrine sweat glands (ECK-rin):
Body's most numerous sweat glands, whichproduce watery sweat to maintain normal bodytemperature.
Epidermis (ep-i-DER-miss):
Thin, outer layer of the skin.
Epithelial tissue (ep-i-THEE-lee-al):
Tissue that covers the internal and externalsurfaces of the body and also forms glandular organs.
Integument (in-TEG-ye-ment):
In animals and plants, any natural outer covering, such as skin, shell, membrane, or husk
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Keratin (KER-ah-tin):
Tough, fibrous, water-resistant protein thatforms the outer layers of hair, calluses, andnails and coats the surface of the skin.
Lunula (LOO-noo-la):
White, crescent-shaped area of the nail bednear the nail root.
Melanocyte (MEL-ah-no-site):
Cell found in the lower epidermis that producesthe protein pigment melanin.
Organ (OR-gan):
Any part of the body formed of two or moretissues that performs a specialized function.
Sebaceous gland (suh-BAY-shus):
Exocrine gland in the dermis that producessebum.
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Sebum (SEE-bum):
Mixture of oily substances andfragmented cells secreted bysebaceous glands.
Squamous cells (SKWA-mus):
Cells that are flat and scalelike.
Subcutaneous (sub-kew-TAY-nee-us):
Tissues between the dermis andthe muscles.
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EPIDERMIS
The outer part of the skin
Made up of stratified squamous
epithelium that is capable of keratinizing of becoming hardand tough.
It is avascular Most cells of of the EPIDERMISare keratinocytes
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5 LAYERS OF THE EPIDERMIS
1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum
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Stratum basale
the deepest cell layer of the epidermis.
Lies closest to the dermis and contains the only
epidermal cells that receive adequate nourishment
via diffusion of nutrients from the dermis. These cells are constantly undergoing cell
divisions, and millions of cells are produced daily.
The daughter cells are produced upward, away
from the source of nutrition, to become part of the
epidermal layers closer to the skin surface.
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The stratum basale moves away from the dermisand become part of the superficial layers, thestratum spinosum and the stratum granulosum.Then they become flatter, increasingly full of
keratin and finally die, forming the clear stratumlucidum.
This latter epidermal layer occur only when theskin is hairless and extra thick, that is, on the palmof the hand and soles of the feet.
The outermost layer, the stratum corneum is 20-30
cell layers thick. About ¾ of the epidermalthickness. The shingle-like cells remants ,completely filled with keratin.keratin is anexceptionally tough protein.Its abundance allows the stratum corneum itsdurable ́ overcoatµ of the body.
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Epidermis contains the
following cells:
Keratinocytes
Melanocytes
Langerhans Cells
Merker Cells
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Keratinocytes
Most cells of of the EPIDERMIS are
keratinocytes (About 90 percent of thecells)
named because they produce a tough,
fibrous protein called keratin.
Keratin-the main structural protein of the epidermis, and it provides many of
the skin·s protective properties.
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arranged in layers, with the youngest cells in thelower layers and the oldest cells in the upper layers.
The old keratinocytes at the surface of the skin
constantly slough off. Meanwhile, cells in the lower layers of the
epidermis divide continually, producing newkeratinocytes to replace those that have sloughedoff.
As keratinocytes push up through the layers of the
epidermis, they age and, in the process, producekeratin.
By the time the cells reach the uppermost layer of the epidermis, they are dead and completely filledwith the tough protein.
Healthy epidermis replaces itself in a neatlyorchestrated way every month.
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Melanocytes
Skin Color Three pigments contribute to skin
color:í The amount and kind (yellow, reddish
brown, or black) of melanin of theepidermis.
í The amount of carotene deposited in thestratum corneum and subcutaneous
tissue.í The amount of oxygen bound to
hemoglobin (pigment in the RBC) in thedermal blood vessels.
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cells that produce a dark pigment
called melanin.
Melanin pigment that gives color to the skin and
protects it from the sun·s ultraviolet rays.
After being produced in the melanocytes,
packets of melanin called melanosomes
transfer to the keratinocytes. There they are arranged to protect the
deoxyribonucleic acid (DNA), or genetic
material, of the keratinocytes.
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All people have roughly the same number of melanocytes.
Differences in skin color, such as that
between light-skinned people of Europeandescent and dark-skinned people of Africandescent, result from differences in theamount of melanin produced and howmelanosomes are arranged in thekeratinocytes.
Particularly in people with light skin,melanin sometimes accumulates inpatches, forming freckles, age spots, or liver spots.
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In people of almost any skin tone, exposure to thesun causes melanocytes to increase their production of melanin to help protect the skin.
This process results in a darkening of the skin tone
to form a suntan. The suntan fades when keratinocytes containing
the extra melanin are sloughed off.
A type of melanin called pheomelanin makesredheaded people more sensitive to the sun. A totallack of melanin, a genetic condition called
albinism, makes people extremely sensitive to thesun.
People with albinism can be members of any raceand have very light skin, hair, and eyes.
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Langerhans cell
Produced in the bone marrow,
Langerhans cells take up
sentrylike positions in theepidermis, where they help cells
of the immune system recognize
potentially dangerousmicroorganisms and chemicals.
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Merkel cell
found in sensitive, hairless
areas such as the fingertips and
lips.
Located in the deepest layer of
the epidermis, Merkel cells
contact nerve endings in thedermis below and function as a
type of touch receptor.
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2. DERMIS
Inner part of the skin
It is a strong stretchy envelope
that helps to hold the body
together
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Collagen
The main structural component of the dermis
Bundles of collagen molecules pack together throughout the dermis, accounting for three-fourths of the dry weight of skin.
Collagen is also responsible for the skin·sstrength.
Elastin
the main component of elastic fibers.
These protein bundles give skin its elasticity³ the ability to return to its original shape after stretching.
Collagen and elastin are produced by cells calledfibroblasts, which are found scattered throughoutthe dermis.
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Dermis
richly supplied with bloodvessels and sensory nerve
endings. The dense (fibrous) connective
tissue making up the dermisconsists of two major regions
1. Papillary region
2. Reticular region
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Papillary Layer Upper dermal region
It is uneven and has fingerlike projectionsfrom its superior surface called dermalpapillae, which indent the epidermisabove.
Many of the dermal papillae containcapillary loops, which furnish nutrients tothe epidermis.
Others house pain receptors and touchreceptors are called Meissner·s
corpuscles. On the palms of the hands and the soles of
the feet, the papillae are arranged indefinite patterns that fom looped andwhorled ridges on the epidermal surfacethat increase friction and enhance thegripping ability of the fingers and feet.
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Reticular Layer The deepest skin layer
It contains blood vessels, sweat and
oil glands, and deep pressure
receptors called paciniancorpuscles.
Many phagocytes are found here.
They act to prevent bacteria that
have managed to get through theepidermis from penetrating any
deeper into the body.
Both collagen and elastic fibers are
found throughout the dermis
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APPENDAGES OF THE
SKIN The skin appendages include
cutaneous glands, hair and hair
follicles and nails.
Each of the appendages arises
from the epidermis and plays a
unique role in maintaining bodyhomeostasis.
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Cutaneous Glands
all exocrine glands that release their
secretions to the skin surface via
ducts. fall into two groups: sebaceous
glands and the sweat glands.
these glands are formed by the
stratum basale, thus they push intodeeper skin regions and ultimately
reside almost entirely in the dermis.
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1. Sebacous (oil) Glands
found all over the skin, except in the
palm of the hands and soles of the
feet. have ducts that usually empty into a
hair follicle, but some open directly
to the skin surface.
the product of sebaceous glands,sebum, is a mixture of oily
substances and fragment cells.
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Sebum is a lubricant that keeps the skinsoft and moist and prevents the hair frombecoming brittle.
Sebum also contains chemicals that killbacteria, so it is important in preventingthe bacteria present on the skin surfacefrom invading the deeper skin regions.
The sebaceous glands become very activewhen male sex hormones are produced inincreased amounts during adolescence.
Thus the skin tends to become oilier duringthis period of life.
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2. Sweat Glands
Also called sudoriferous glands
widely distributed in the skin
(2.5 million per person)
there are two types of sweat
glands :
a. eccrine glandsb. apocrine glands
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Eccrine glands
found all over the body and are
far more numerous than
apocrine glands
produce sweat, a clear
secretion that is primarily water
plus some salts, vitamin C,traces of metabolic wastes
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Sweat sweat is acidic (pH 4-6), a characteristic that
inhibits the growth of bacteria, which are alwayspresent in the skin surface.
Sweating Sweat reaches the skin surface via a duct that
opens externally as a funnel-shaped pore. Theeccrine sweat glands are important and highlyefficient part of the body·s heat-regulatingequipment. They are supplied with nerve endings
that cause them to secrete sweat when theexternal temperature is high. When sweatevaporates off the skin surface, it carries largeamount of body heat with it.
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Apocrine sweat glands
largely confined to the axillary and genital areas of the body.
Usually larger that eccrine glands, and their ductsempty into hair follicles.
Their secretion contains fatty acids and proteins,aswell as the substances present in eccrinesecretion.
Consequently, it may have a milky yellowish color.
The secretion is odorless but when bacteria thatlive on the skin use its proteins and fats as a
source of nutrients for their growth, it takes on amusky, unpleasant odor.
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Hair
Roughly 5 million hairs cover the
body of an average individual. About
100,000 of those hairs appear on thescalp. Almost every part of the body
is covered by hair, except the palms
of the hands, the soles of the feet,
the sides of the fingers and toes, thelips, and certain parts of the outer
genital organs.
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produced by a hair follicle and is a flexible epithelialstructure.
The part of the hair enclosed in the follicle is called theroot.
The part projecting from the surface of the scalp or skinis called shaft.
Each hair consist of a central core called the medullasurrounded by a bulky cortex.
The cortex is, in turn, enclosed by a outermost cuticleformed by a single layer of cells that overlap one another like shingles on a roof.
A hair is formed by division of the well-nourished stratumbasale epithelial cells in the growth zone, or hair bulbmatrix, at the inferior end of the follicle. Hair on the scalptypically grows at a rate of 1 mm (0.04 in) every threedays.
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Hair Growth
A hair grows upward fromthe root. Lengtheningfibers of keratin-filleddead cells, grouped
around the semihollowmedulla, make up thecortex. A living structurecalled the bulb (visible asa white lump at the endof a plucked hair) surrounds and feeds the
root, which lies in apocket of the epidermiscalled the follicle. Hair grows fastest when it isshort.
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Each hair follicle also contains the arrector pili, a muscle that contracts in response tocold, fright, and other emotions. When the
muscle contracts, it pulls the hair in thefollicle into a vertical position. Thisresponse may help some mammals keepwarm or look bigger to frighten or intimidate their enemies. But in humans,
again because of our sparse coat of bodyhair, it merely produces ´goose bumps.µ
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The color of hair is due to melanin, produced bymelanocytes in the bulb of the hair follicle and thenincorporated into the keratinocytes that form thehair. Dark hair contains true melanin like that found
in the skin, while blond and red hair result fromtypes of melanin that contain sulfur and iron. Hair goes gray when melanocytes age and lose theenzyme necessary to produce melanin. White hair occurs when air bubbles become incorporated intothe growing hair. The texture of hair results fromthe shape of the hair shaft. Straight hair appears
round in cross section, wavy hair has an oval shapein cross section, and the cross section of a curlyhair has an elliptical or kidney-shaped appearance.
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NAIL
A scalelike modification of theepidermis that corresponds to thehoof or claw of other animals.
Each nail has a free edge, a body,and a root.
They protect the ends of the digitsfrom injury, help us grasp small
objects, and enable us to scratch. made of hard, keratin-filledepidermal cells
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PARTS OF THE NAIL
The borders of the nail areoverlapped by skin folds, called nailfolds.
The thick proximal nail fold iscommonly called cuticle.
The stratum basale of the epidermisextends beneath the nail as the nail
bed. Its thickened proximal area is calledthe nail matrix.
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Nail are transparent and nearly colorless,but they look pink because of the richblood supply in the underlying dermis. The
exception to this is the region over thethickened nail matrix that appears as awhite crescent and is called the lunula.This area appears white due to anunderlying thick layer of epidermis that
does not contain blood vessels. Fingernails typically grow 1 mm (0.04 in)
per week. Toenails generally grow moreslowly.
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Human fingernailsand toenails are madeof dead cellscontaining the proteinkeratin. Nails havethree parts: theconcealed root, thebody, which isexposed but attached
to skin, and the edge.The nail grows outfrom the addition of new cells at the root.