Chapter 4: Skin and Body Membranes

Skin and Body MembranesRemember an organ is where 2 or more kinds

of tissues work together to perform some specific function

SKIN: epithelial, connective, muscle and nervous tissue

Integument: the membranes of the body that cover, line and protect.

Includes skin, hair, nails and other membranes

Types of Body MembranesEpithelial membranes

Cutaneous membranesMucous membranesSerous membranes

Connective tissue membranesSynovial membranes

Serous MembranesLines body cavities—covers organs in the

thorax and abdomenConsists of simple squamous epithelial tissue

and a thin layer of connective tissue2 layers of epithelium

Visceral layer covers the outside of the organ

Parietal layer lines a portion of the wall of ventral body cavity

Serous MembranesCells of this membrane secrete a clear fluid (serous) between the two layers which helps to lubricate the organs and cavities they are in

Serous Membranes

Specific serous membranesPeritoneum

-Abdominal cavityPleura

-Around the lungsPericardium

-Around the heart

Mucous Membranes•Line body cavities that are open to exterior •Ex: nasal and oral cavities•Also in tubes of the respiratory, digestive, urinary and reproductive systems.•Cells in this membrane secrete mucus•Goblet cells make mucus

Cutaneous MembraneCutaneous membrane = skin

Connective Tissue Membrane

Synovial membraneFound in the linings of the joint cavities between the ends of bonesSecretes a thick colorless fluid that lubricates the joint

Integumentary SystemFunctions: Protective covering,

regulates body temperature, contains sense organs and excretes waste.

Produces Vitamin D in response to UV radiation. This helps the body absorb calcium

Skin LayersEpidermis—outer layer

Stratified squamous epitheliumSheds every 30 days

Dermis-inner layerThicker than epidermisIncludes connective and nervous tissue as well as muscle tissue

Skin LayersSubcutaneous (hypodermis) Not really considered a layer of skin but

found underneath the dermis is deep to dermis

Anchors skin to underlying organsComposed mostly of adipose tissueBlood vessels for skin are here

EpidermisLacks blood vesselsCells at very top are far away from blood

vessels below and eventually die.They still provide protection even though

they are not functional cellsThese cells have keratinizedKeratin is a waterproof protein that forms

in the skin cells as they mature

EpidermisThe epidermis shields the underlying

tissue from water loss and injuryAlso protects against invasion of microbes

and bacteriaMelanin is found here.Melanin is a dark pigment produced by

melanocytesThe job of melanin is to absorb light

energy to protect skin from damage.

EpidermisIf your skin does not

have enough melanin you are at risk for a sunburn.

We all have the same number of melanocytes but genetics determine how much melanin our cells produce

EpidermisThose people with

dark skin have ancestors that live near the equator or at the poles. (both places have periods of direct sunlight)

Color is yellow to brown to black

Epidermis•Skin color is also determined by oxygen content. •Most of us have a pinkish cast to our skin because of high oxygen •Person with oxygen poor blood because of disease or injury have a bluish cast to their skin.•This is called cyanosis

Stratum Basale; lowest layer of epidermisMitosis takes place

hereStratum corneum; top

layer of epidermisAll cells here are

dead

DermisBinds epidermis to the subcutaneous layerMade of fibrous connective tissue, blood vessels,

nerve fibers, muscle tissue, sebaceous (oil) glands and sweat glands

Thickest layer of skinCollagen and elastin: fibers that give skin elasticity

(ability to return to original shape) and extensibility (ability to stretch)

Lack of collagen and elastin = wrinkles!Papillary layer (all dermal papillae) causes

fingerprints

Figure 4.4

SPF-Preventing sun damaged skinWhat is SPF?Is a higher SPF better?Are tanning beds safe?

Accessory Organs--Hair

Consists of hard keratinized epithelial cellsHair follicle extends from dermis to surface of

skin. Contains the rootHair growth—scalp hair grows for about 3 years,

then rests for oneNormal hair loss per day is about 100 hairsAndrogens are necessary for hair growth, but too

much can cause hair loss (male pattern baldness)

Accessory Organs--HairMelanocytes provide pigment for hair colorHair color is determined by the amount of melanin produced by the melanocytesarrector pili muscle: attached to the hair follicle. When it contracts it causes the hair to stand on end. Goose bumps!

Sebaceous glands: associated with hair follicle, produce oily secretion called sebum.

Sebum: mixture of fatty material and dead cells—keeps hair and skin soft to prevent dry and cracked skin.

Hair follicle with sebum stuck in them= blackhead

Black is oxidized oil—not dirt If bacteria present can form pimple or boil

Accessory Organs—Sebaceous Glands

Figure 4.6a

Sweat glands: sudoriferous glands that occur in the skin

They originate in the dermis

Accessory Organs—Sweat Glands

Two types of sweat glands:Eccrine: associated with pores, produce sweat in

response to increased body temperature: begin working right after birth, found all over the body

Apocrine: associated with hair follicles produce sweat in response to stress; begin working at puberty. Contains a higher fat content than normal sweat. Found mainly in armpits, genital area and around breasts. Theorized that this sweat contains pheromones. (thicker and stickier than regular sweat)

Accessory Organs—Sweat Glands

Sweat and Its FunctionComposition

Mostly waterSalts and vitamin CSome metabolic wasteFatty acids and proteins (apocrine only)

FunctionHelps dissipate excess heatExcretes waste products

Odor is from associated bacteria

Scale-like modifications of the epidermisHeavily keratinized

Lack of pigment makes them colorlessBody is the visible attached portionRoot of nail embedded in skinCuticle is the proximal nail fold that

projects onto the nail body

Accessory Organs—Nails

Figure 4.9

Clinical Application

The pink color of the nail bed is clinically significant in that it can aid in the assessment of perfusion (blood flow) to the extremities and can be a determinant of oxygenation. If you pinch one of your fingernails straight down with the thumb and index finger for 5 seconds you will note that your nail bed went from a blanched white color back to pink in a matter of seconds (good profusion). If it takes longer than 3 seconds for the nail bed to “pink up” then profusion to the extremities is considered sluggish. This test is called capillary refill time.

Regulation of body temperatureAs body temp increases blood vessels

dilate and carry hot blood to the surface to release heat to the atmosphere.

Sweat glands (eccrine) send sweat to the surface to cool the body through evaporation.

Regulation of body temperatureAs body temperature decreases blood

vessels constrict to prevent blood from flowing to the surface, thereby conserving heat

Shivering also occurs; muscle contractions produce heat through friction

Arrector pili muscles contract.

Change detected by receptor

Stimulus: Increased body temperature

Input:Informationsent along afferentpathway to

HypothalamusBlood VesselsSweat Glands

Body Temperature

Blood vessels dilatecausing heat to radiatefrom the bodySweat Glands become active, cooling throughevaporation.

Output:Information sent along efferentpathway to activate

Brain

1

2

4

5

3

Imbalance

Imbalance

The Integumentary System: Negative Feedback

Change detected by receptor

Stimulus: Decreased body temperature

Input:Informationsent along afferentpathway to

HypothalamusBlood VesselsSweat GlandsMuscles

Body Temperature

Blood vessels constrictSweat Glands become less active, muscles Shiver to generateheat

Output:Information sent along efferentpathway to activate

Brain

1

2

4

5

3

Imbalance

Imbalance

The Integumentary System: Negative Feedback

Skin Homeostatic ImbalancesMacule-discolored spot;

freckle

Wheal-localized elevation of the skin that is often accompanied by itching; contact dermatitis

Skin Homeostatic ImbalancesPapule-solid

circumscribed, elevated area on the skin; pimple

Nodule- larger papule; acne vulgaris

Vesicle-small fluid filled sac; blister (a bulla is a larger one; chicken pox)

Comedo-yellow or black plug in the skin; blackhead

Skin Homeostatic Imbalances

Pustule-small, elevated, circumscribed lesion of the skin that is filled with pus; whitehead

Erosion (Ulcer)-an eating or knowing away of tissue; decubitus ulcer

Skin Homeostatic Imbalances

Crust-dry, serous, brown, yellow, red or green exudation; eczema

Scale-thin, dry flake of epithelial cells; psoriasis

Skin Homeostatic Imbalances

Fissure-crack like sore or slit that extends through the epidermis into the dermis; athlete’s foot

Cyst-closed sac under the skin; sebaceous cyst

Skin Homeostatic Imbalances

Skin Homeostatic ImbalancesBurns

Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals

Associated dangersDehydrationElectrolyte imbalanceCirculatory shock

Rule of NinesWay to determine the extent of burnsBody is divided into 11 areas for quick

estimationEach area represents about 9% of total

body surface area

Rule of Nines

Severity of BurnsFirst-degree burns

Only epidermis is damagedSkin is red and swollen

Second-degree burnsEpidermis and upper dermis are damagedSkin is red with blisters

Third-degree burnsDestroys entire skin layerBurn is gray-white or black

Severity of Burns

Figure 4.11b

Critical BurnsBurns are considered critical if

Over 25% of body has second-degree burns

Over 10% of the body has third-degree burns

There are third-degree burns of the face, hands, or feet

Skin CancerCancer—abnormal cell massClassified two ways

BenignDoes not spread (encapsulated)

MalignantMetastasized (moves) to other parts of the

bodySkin cancer is the most common type of

cancer

Skin Cancer TypesBasal cell

carcinomaLeast malignantMost common

typeArises from

stratum basale

Skin Cancer TypesSquamous cell

carcinomaMetastasizes to lymph

nodes if not removedEarly removal allows a

good chance of cureBelieved to be sun-

induced

Skin Cancer TypesMalignant melanoma

Most deadly of skin cancers

Cancer of melanocytesMetastasizes rapidly to

lymph and blood vessels

Detection uses ABCD rule

ABCD RuleA = Asymmetry

Two sides of pigmented mole do not matchB = Border irregularity

Borders of mole are not smoothC = Color

Different colors in pigmented areaD = Diameter

Spot is larger than 6 mm in diameter

Aging Skin The amount of subcutaneous

tissue below the skin decreases, leading to an intolerance to cold in the elderly.

Because of decreased oil production and declining numbers of collagen fibers, the skin becomes drier and may become itchy and bothersome.

Aging SkinThinning of the skin

makes it more susceptible to bruising and other types of injuries.

A decrease in elasticity of the skin, along with the loss of subcutaneous fat, allows bags to form under the eyes and causes jowls to sag.

Aging SkinTo delay these

changes, the skin should be kept clean and shielded from the sun, and a healthy diet with plenty of fluids should be maintained.