Anatomy - Ch. 4 - Skin & Body Membranes

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Body Membranes

covers surfaces, lines body cavities, and forms protective sheet around organs.

2 groups of body membranes

1.) epithelial membrane - cutaneous, mucous, & serous membranes.
2.) connective tissue membrane - synovial membrane

Epithelial membrane

• aka. covering & lining membrane.
• contain epithelial sheet always combined with underlying layer of connective tissue.

Cutaneous membrane

• skin
• superficial epidermis - keratinizing stratified squamous epithelium
• underlying dermis - dense fibrous connective tissue layer
• exposed to air (dry membrane)

Mucous membrane

• composed of epithelium resting on lamina propria
• lines all body cavities open to exterior
• "wet," moist membrane that is continuously bathed in secretions.
• adapted to secretions or absorption.

lamina propria

loose connective tissue

Serous membrane

• composed of simple squamous epithelium resting on thin layer of areolar connective tissue.
• occurs in pairs
• has serous fluid

Pair of serous membrane

1.) parietal layer
2.) visceral layer

parietal layer of serous membrane

lines specific portion of the wall of the ventral body cavity.

visceral layer of serous membrane

covers the outside of the organs in the cavity.

serous fluid

• thin, clear fluid that separate serous layers.
• allows organs to slide easily across the cavity wall & one another without friction as they carry routine functions.

Examples of serous membranes

• peritoneum
• pleural
• pericardium

peritoneum

lines abdominal cavity & covers organs

pleural

surrounds the lungs

pericardium

surrounds the heart

Synovial membrane

• soft areolar connective tissue & contain no epithelial cells.
• line fibrous capsules surrounding joints.
- provides smooth surface & secrete a lubricating fluid.
• line bursae

bursae

• small sacs of connective tissue & tendon sheaths.
• cushions organs moving against each other during muscle activity.

Integumentary system

skin & derivatives (sweat, oil glands, and nails)

Integument

• "covering the skin"
• keeps water & other molecules in the body.
• insulates & cushions the deeper body organs.
• protects entire body.
• regulates heat loss from body surface.
• acts as mini-excretory system
• manufactures proteins important for immunity & synthesizes Vitamin D.

Integument as mini-excretory system

urea, salts, and water are lost from sweating.

Integument protection of the body

• Mechanical damage - bumps & cuts.
• Chemical damage - acids & bases.
• Thermal damage - hot & cold
• Ultraviolet radiation - sunlight
• bacteria

cutaneous sensory receptors

include touch, pressure, temperature, & pain receptors about external environment.

Tissues that make up the skin

1.) epidermis
2.) dermis

Epidermis

• made up of stratified squamous epithelium.
• capable of keratinizing, or becoming hard & tough.

blister

interstitial fluid accumulating in between layers due to burn or friction.

subcutaneous tissue (hypodermis)

• deep to dermis
• adipose tissue
• not part of skin, but anchors the skin underlying organs.
• serves as shock absorber.
• insulates deeper tissues from extreme temperature changes occurring outside the body.

5 layers of epidermis (from inside out)

1.) stratum basale
2.) stratum spinosum
3.) stratum granulosum
4.) stratum lucidum
5.) stratum corneum

stratum basale

• deepest cell layer of epidermis.
• lies closest to the dermis.
• contains epidermal cells that receive adequate nourishment via diffusion of nutrients from dermis.
• aka. stratum germinativum.

stratum germinativum

• always undergoing cell division.
• move away from source of nutrition towards the surface of the epidermal layers.
- move through stratum spinosum --> stratum granulosum --> finally die, forming stratum lucidum.

stratum lucidum

• not present in all skin regions.
• occurs only where skin is hairless & extra thick.
- palms of hands & soles of feet.
• unable to get O2 & nutrients.

stratum lucidum unable to get O2 & nutrients

• full of keratin
• secretes H20-repelent glycolipid in extracellular space.
• distant from blind supply.

stratum corneum

• outermost layer
• 20-30 cell layers thick (3/4 epidermal thickness)
• durable "overcoat" for body.
• sheds dandruff

stratum corneum "overcoat"

protects deeper cells from hostile external environment, water loss & helps resist biological, chemical, & physical assaults.

dandruff

• average person sheds 18kg (40 lbs)
• provides food source for dust mites.

melanin

• pigment that ranges in color from yellow to brown to black.
• produced by melanocytes.

melanocytes

• spider-shaped cells
• found in stratum basale.
• stimulated by sunlight to produce melanin pigment (tanning).

melanosomes

membrane-bound granules that have an accumulation of melanin.

keratinocytes

• produce keratin
• contains melanin that shields DNA from damaging effects of U.V. radiation in sunlight.

keratin

• fibrous protein that makes epidermis a tough protective layer
• uppermost layer of the skin.
• cornified/hardened
• helps prevent water loss from body surface.

Freckles & moles

spots where melanin is concentrated.

herpes simplex

• cold sore
• more likely to erupt after sunbathing.

dermis

• strong, stretchy envelope that helps hold body together.
• dense (fibrous) connective tissue.
• 2 major regions

major regions of dermis

1.) papillary area
2.) reticular area

papillary layer

• upper dermal region
- has dermal papillae on its superior surface.

dermal papillae

• uneven & has peg-like projections from its superior surface.
• indent the epidermis above.
• contain capillary loops - furnish nutrients to the epidermis.

free nerve endings

house pain receptors

Meissner's corpuscles

touch receptors

fingerprints

identifying films of sweat from sweat pores.

reticular layer

• deepest skin layer
• contains blood vessels, sweat & oil glands, & Pacinian corpuscles.
• have phagocytes

Pacinian corpuscles

deep pressure receptors.

phagocytes

prevent bacteria from penetrating any deeper into the body.

collagen

• responsible for toughness of the dermis.
• attract & bind water & help keep skin hydrated.

elastic fibers

• give skin its elasticity.
• fibers decrease in age.

dermis supplied with blood vessels

• maintain body temperature at homeostasis.

increased body temperature

• capillaries of dermis becomes engorged, or swollen, with heated blood.
- skin becomes reddened or warm.

decreased body temperature

• body conserves heat.
• blood bypasses dermis capillaries, keeping body temperature high.

decubitus ulcers (skin ulcer)

• occurs in bedridden patients who are not turned regularly or who are dragged or pulled across the bed repeatedly.
• pressure on body restricts blood supply & skin becomes pale or blanched.
• permanent damage eventually results in degeneration & ulceration of skin.

3 pigments of skin color

1.) amount & kind (yellow, reddish brown, or black) of melanin in the epidermis.
2.) amount of carotene deposited in the stratum corneum & subcutaneous tissue.
3.) amount of oxygen-rich hemoglobin in dermal blood vessels.

carotene

orange-yellow pigment, mainly found in carrots.

cyanosis

• skin appearing blue because hemoglobin is poorly oxygenated.
• common during heart failure & severe breathing disorders.
• black people's skin masks the effects of melanin but is apparent in mucous membranes & nail beds.

skin color influenced by emotion

• redness, or erythema
• pallor, or blanching
• Jaundice, or yellow cast.
• Brusies, or black-&-blue marks.

Redness (erythema)

indicates embarrassment (blushing), fever, hypertension, inflammation, or allergy.

Pallor (blanching)

• people become pale under certain types of emotional stress.
• can signify anemia, low blood pressure, or impaired blood flow to area.

Jaundice (yellow cast)

• yellow skin tone usually signifying liver disorder in which excess bile pigments are absorbed into blood, circulated throughout the body, & deposited in body tissues.

Bruises (black-or-blue marks)

• sites where blood has escaped from circulation & has clotted in the tissue spaces.
• hematomas - masses of blood clots.

skin appendages

• cutaneous glands, hair & hair follicles, & nails.
• arises from epidermis & play unique role in maintaining body homeostasis.

exocrine glands (cutaneous glands)

• release their secretions to the skin surface via ducts.

groups of exocrine glands

1.) subaceous (oil) glands
2.) sweat glands

sebaceous (oil) glands

• found all over skin except on palms of hands & soles of feet.
• ducts empty into a hair follicle.
• produces sebum.

sebum

• mixture of oily substances & fragmented cells.
• lubricant that keeps skin soft & moist.
• prevents hair from becoming brittle.
• contains chemicals that kill bacteria & prevent bacteria on skin surface from invading skin regions.

whitehead

sebaceous gland duct blocked by sebum.

blackhead

darkened, accumulated oxidized and dried material on skin.

acne

active infection of the sebaceous gland accompanied by pimples on skin.

Seborrhea

• aka "cradle cap"
• found on infants.
• overactivity of sebaceous glands
• begins on scalp as pink, raised lesions that gradually from a yellow to brown crust that sloughs off oily scales.

Sweat glands

• aka sudoriferous glands
• 2.5 million per person.

Types of sweat glands

1.) eccrine glands
2.) apocrine glands

eccrine glands

• more numerous & found all over the body.
• supplied with never endings that cause then to secrete sweat when external temperature or body temperature is high.

sweat

• clear secretion that is primarily water + salts (sodium chloride), vitamin C, metabolic wastes (ammonia, urea, uric acid), & lactic acid.
• acidic (pH 4-6) - inhibits growth of bacteria.
• body can lose up to 7 liters of water.

lactic acid

chemical that accumulates during vigorous muscle activity.

apocrine glands

• confined to axillary & gential areas.
• larger than eccrine glands.
• secretion contains fatty acids + proteins + eccrine secretions.
• begin to function during puberty under influence of androgens (male sex hormones).

apocrine gland secretion

• milky or yellowish color.
• secretion is odorless but when bacteria that live on skin use its proteins & fats as nutrient source for growth, takes on musky unpleasant odor.

hairs

• serves minor protective functions
• flexible epithelial structure.

minor protective functions of hair

• guard head against bumps.
• shield eyes (eyelashes)
• keep foreign particles out of respiratory tract (nose hairs)

root

part of hair enclosed in the follicle.

shaft

part of hair projecting from the surface of the scalp or skin.

matrix

growth zone in hair bulb from stratum basale epithelial cells, growing further away from region until keratinized and die.

medulla

central core of a hair

cortex

bulky layer that surrounds the medulla

cuticle

• surrounds the cortex.
• single layer of cells that overlap one another like shingles on a roof.
- keeps hair apart & from matting.
• most heavily keratinized region.

split ends

• cuticle is most subject to abrasions - tends to wear away at tip of shaft, allowing keratin fibers in the inner hair regions to frizz out.

smooth & silky hair

hair shaft is oval

curly or kinky hair

hair shaft is flat & ribbon-like.

straight & coarse hair

hair shaft is perfectly round

hair follicle

composed of epidermal sheath & dermal sheath.

epidermal sheath

• inner hair follicle
• composed of epithelial tissue and forms the hair.

dermal sheath

• outer hair follicle
• dermal connective tissue

papilla

provides blood supply to the matrix in the hair bulb.

arrector pili

• aka. "raiser of hair"
• connect each side of the hair follicle to the dermal tissue.

goose bumps

• arrector pili pulls hair upright, dimpling the skin surface.
• more useful on animals than on humans.

nail

scale-like modification of the epidermis that corresponds to the hoof or claw of other animals.

free edge

• body of nail.
• visible attached portion.

nail root

embedded in the skin

nail folds

skin folds that overlap and border the nail.

nail cuticle

thick proximal nail fold.

nail bed

stratum basale of the epidermis that extends beneath the nail.

nail matrix

thickened proximal area responsible for nail growth.

lunula

white crescent region over the thickened nail matrix.

athlete's foot

• aka. tinea pedis.
• itchy, red, peeling condition of the skin between the toes, resulting from fungus infection.

boils

• inflammation of hair follicles and sebaceous glands.
• common on the dorsal neck.

carbuncles

• Staphylococcus auereus
• composite boils typically caused by bacterial infection.

cold sores (fever blisters)

• small fluid-filled blisters that itch and sting.
• caused by herpes simplex infection.
• virus localizes in a cutaneous nerve - remains dormant until activated by emotional upset, fever, or UV radiation.
• usually occur around the lips and in oral mucosa of mouth.

contact dermatitis

• itching, redness, and swelling of the skin, progressing to blistering.
• caused by exposure of skin to chemicals (poison ivy) that provoke allergic responses in sensitive individuals.

impetigo

• pink, water-filled, raised lesions that develop a yellow crust and eventually rupture.
• commonly around the mouth and nose.
• caused by highly contagious staphyloccus infection
• common in elementary school-aged children.

psoriasis

• chronic condition, characterized by overproduction of skin cells that results in reddened epidermal lesions covered with dry, silvery scales that itch, burn, crack, and sometimes bleed.

burn

• tissue damage and cell death caused by intense heat, electricity, UV radiation (sunburn), or certain chemicals (acids).
• body loses fluids of containing proteins & electrolytes.
- can lead to kidney failure and circulatory shock.

circulatory shock

inadequate circulation of blood caused by low blood volume.

rule of nines

• determines how much of the body surface is burned.
• divides body into 11 areas --> 9% each area + 1% (around genitals).

first-degree burn

• only epidermis is damaged.
• area becomes red and swollen.
• not usually serious & generally heal in 2-3 days without any special attention
• Ex: sunburn.

second-degree burn

• injury to the epidermis and upper region of the dermis.
• skin is red and painful, & blisters appear.
• regrowth (regeneration) of epithelium can occur
• no scaring if taken care of to prevent infection.

partial-thickness burns

first- & second- degree burns.

third-degree burns

• aka full-thickness burns
• destroy entire thickness of skin
• burned area appears blanched (gray-white) or blackened.
• never endings are destroyed so burn area is not painful.
• regeneration is not possible.

conditions of critical burns

1.) Over 25% of body has second-degree burns.
2.) Over 10% of the body has third-degree burns, or
3.) There are third-degree burns of the face, hands, or feet.

Basal Cell Carcinoma

• least malignant and most common skin cancer.
• stratum basale altered so keratin is not formed.
• cancer lesions occur most often on sun-exposed area of the face - appear as shiny, dome-shaped nodules that later develop a ulcer with "pearly" beaded edge.
• slow-growing, metastasis occurs before noticed.
• full cure - 99% of lesions removed surgically

Squamous Cell Carcinoma

• arises from stratum spinosum.
• lesions appear scaly, reddened papule - form shallow ulcer with firm, raised border.
• appears most often on scalp, ears, dorsum of hands, & lower lip.
• grows rapidly & metastasizes to adjacent lymph nodes if not removed.
• believed to be sun-induced.
• cure - removed surgically by radiation therapy.

Malignant Melanoma

• cancer of melanocytes
• arises from accumulated DNA damage in skin cell
• appears as spreading brown to black patch.
• metastasizes rapidly surround lymph & blood vessels.
• 50% survival rate.

ABCD Rule

• for recognizing melanoma
• (A) Asymmetry
• (B) Border irregularity
• (C) Color.
• (D) Diameter

Asymmetry (ABCD rule)

2 sides of pigmented spot or mole do not match.

Border irregularity (ABCD rule)

Borders of lesion are not smooth but exhibit indentations.

Color (ABCD rule)

Pigmented spot contains areas of different colors (blacks, browns, tans, & sometimes blues and reds).

Diameter (ABCD rule)

spot is larger than 6 milimeters in diameter.

lanugo

• downy type of hair covered on soon-to-be-born infants.
• hairy cloak usually shed by birth.

vernix caseosa

• white, cheesy-looking substance covering skin of newborn.
• produced by sebaceous glands
• protects baby's skin while floating in water-filled sac inside mother.

milia

• small white spots on baby's nose & forehead due to accumulations in the sebaceous glands.
• normally disappear by the third week after birth.

dermatitis

• skin inflammation

alopecia

hair thinning & some degree of baldness.

male pattern baldness

men bald as they age.

vellus

hair folliciles degenerate & hairs appear colornless & very tiny.

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