chapter 4: skin and body membranes. skin and body membranes remember an organ is where 2 or more...
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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.