Lecture 4 Integumentary

8/3/2019 Lecture 4 Integumentary

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INTEGUMENTARY

SYSTEM

formed by the skin, hair, nails, and

associated glands, and wraps the body.



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.



12 good reasons whythe integumentary

system is so importantto us!



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.



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.



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.



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.



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.)



6. It stores some

vitamins.

It reacts with the sunlight andmanufacture vitamin D.



. 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.



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.



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.



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.



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.



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.



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



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.



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.



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



5 LAYERS OF THE EPIDERMIS

1. Stratum basale

2. Stratum spinosum

3. Stratum granulosum

4. Stratum lucidum

5. Stratum corneum



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.



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.



Epidermis contains the

following cells:

Keratinocytes

Melanocytes

Langerhans Cells

Merker Cells



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.



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.



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.



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.



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.



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.



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.



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.



2. DERMIS

Inner part of the skin

It is a strong stretchy envelope

that helps to hold the body

together



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.



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



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.



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



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.



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.



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.



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.



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



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



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.



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.



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.



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.





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.



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



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.



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



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.



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.



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.

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Lecture 4 Integumentary