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organs that make up the integumentary system

skin, nails, hair follicles, sebaceous glands, sweat glands, specialized nerve endings


one of the largest organs in the body, is .5mm to 4.0 mm thick


superficial region of skin


middle region of skin


superficial fascia- deepest region

skin layer


epithelial tissue that attaches to dermis- keratinized stratified squamous epithelium. HAS NO BLOOD VESSELS (AVASCULAR)

cells of epidermis

keratinocytes, melanocytes, langerhans cells merkel cells (tactile cells)


produce fibrous proteins, 90% of cells, connected by desmosomes, produced in stratum basale and pushed to surface, dead when they reach the surface 25-45 days from production to sloughing off FUNCTION: protective barrier


10-25% of cells in lower epidermis,produce brown-black pigment called melanin, melanin is accumlated in membrane bound granules called melanosomes and transferred to nearby keratinocytes

merkel cells

touch receptors, only present in stratum basale, form a merkel disc for sensation of light touch

everyone has the same number of melanocytes


langerhans cells

immune system cells which detect and present antigens to other immune system cells, macrophages that ingestantigens and activate immune system

5 layers of epidermis

stratum corneum, stratum lucidum, stratum granulosm, stratum spinosum, stratum basale

most superficial layer, 20-30 layers of dead cells represented only by flat membrane sacs filled with keratin. Glycolipids in extracellular space

stratum corneum

three to five layers of flattened cells, organelles deteriorating, cytoplasm full of lamellated granules that release lipids and keratohyline granules

stratum granulosum

several layers of keratinocytes unified by desomoes, cells contain thick bundles of intermediate filaments made of pre-keratin

stratum spinosum

deepest epidermal layer, one row of actively mitotic stem cells, some newly formed cells become part of the more superficial layers

stratum basale

thick skin- bottoms of toes, soles, palms fingertips

5 layers of skin

stratum basale

anchored to basement membrane, consists of single layer of mostly stem cells undergoing mitosis to become keratinocytes, a few melanocytes that create skin pigment and occasionally merkel cells

Stratum Spinosum (prickly layer)

7-10 layers of cells, mostly keratinocytes with a few langerhans cells and some melanin granules

stratum granulosum

thin consists of 3-5 cell layers in which drastic changes in keratinocyte appearance occurs (cells flatten) keratohyaline -granules- precursors to keratin, lamellated granules- waterproofing glycolipids

cells in stratum granulsum die because

they are getting too far away from blood vessels in dermis,, they are programmed to die

stratum lucidum

only found in thick skin of palms, soles, fingerips, and bottoms of toes- 3-5 layers of flat clear dead keratinocytes

stratum corneum

horny layer, 20-30 layers of dead keratinocytes, FUNCTIONS protects from abrasion, penetration, waterproofs,

contains flycolipid between cells to waterproof skin

stratum corneum

serves as a physical barrier again light, heat, microorganisms, water and chemicals

startum corneum


thickening of epidermis due to frequent friction or abrasion

epidermal growth factor

protein hormone which stimulates stratum basale cells to undergo mitosis

found in saliva of many mammals and produced by other cells

epidermal growth factor


second major skin region containing strong flexible connective tissue

cell types include fibroblasts, macrophages and occasionally mast cells


rich supply of blood vessels and nerves, contains glands and hair follicles


Papillary layer (dermis)

superfical layer that makes up 20% of dermis, areolar connective tissue with collagen and elastic fibers and blood vessels

composed of small fingerlike projections called dermal papillae which push up into epidermis

papillary layer

dermal papillae (papillary layer of dermis)

contains capillary loops, meissnesr's corpuscles(touch receptors) and free nerve endings for pain. FUNCTION: to increase surface area of contract between epidermis and dermis, to increase diffusion and bettwe resistance to abrasion


caused by dermal ridges and dermal papillae resulting in erpidermal ridges FUNCTION to increase friction for gripping

reticular layer (deep layer of dermis)

80 % of dermis, dense irregular connection tissue with thich collagen and coarse elastic fibers

collagen fibers in the layer add strendth and resiliency to the skin, elastic fibers provide stretch-recoil properties

reticular layer

contains hair follicles, nerves, sebaceous glands, sweat glands, pacinian corpuscles and blood vessels

reticular layer

cleavage or tension lines

skin markings that seperations between bundles of collagen that run parallel to skin surface

flexure lines

skin markings that are dermal folds that occue at or near joints where the dermis is tightly secured to deeper structures- palms, wrists, fingers, soles and toes

stretch marks (striae)

result from dermal tearing, casused by severe strectching -homeostatic imbalance


result from tearing of weak areolar CT of papillary layer

Subcutaneous tissue (hypodermis and superficial fascia)

composed of adipose tissue, and areolar connective tissue, contains cold senestive nerve endings

pigments that contribute to skin color

melanin, carotene, hemoglobin


different forms that range in color, produce melanocytes located in the stratum basale of the epidermis

accumulates in membrane-bound granules called melanosomes that are moved to ends of melanocytes processes


melanosomes are taken up by basal keratinocytes


local accumulations of melanin results in freckles, moles, and age spots



yellow to orange pigment found in carrots, egg yolks and tomatoes, localizes in the stratum corneul and adipse tissue, most obvious in palms and soles

high consumption of carotene-containing foods gives skin a yellow hue


yellowish skin of some asian people is sue to variants of carotene

false- melanin is the cause


a red pigment in red blood cells, skin is translucent when little melanin and carotene are present (fair people)

red-pink color of blood in dermal capillaries shows through skin as pinkish hue



blood and skin of caucasians appear blue when hemoglobin is poorly oxagentaed- during heart failure, sever respiratory disorders , if a baby does not breath shortly after birth


redness of skin, fever, hyertension, inflammation, allergy, blushing

palor or blanching

pale skin, anemia, low blood pressure, during fear, anger and certain types of emotional stress


abnormal yellowing of the skin caused by a liver disorder(yellow bile pigments)


bronzing of skin sign of addisons disease


blood from ruptured capillaries below skin which clotted beneath the skin


clotted blood masses

derivatives of the epidermis

sweat glands, sebaceous glands, hair and hair follicles, nails

sweat glands

3-4 million per person, 2 types: eccrine and apocrine

eccrine sweat glands

most common type, simple, coiled tubular gland that carries sweat through dermis to surface pores

found everywhere EXCEPT lips, nail beds, nipples, external genitalia ear drums

eccrine sweat glands


hypotonic to plasma, 99% water,some salts, vitamin C FUNCTION: cools body and eliminates waste

apocrine sweat glands

secretes by exocytosis, found in axilla and pubic region, ducts connect to hair follicles so hair conducts secretion into air

bacteria decompose of fat and proteins resulting in odor; stimulated by emotional stress and sexual excitement

apocrine sweat glands

mammary gland

sweat glands specialized to secret milk

ceruminous glands

found in skin of external ear canal to secrete ear wax

sebaceous glands

widely distributed except on the palmer and planter surfaces of hands and feet,

develops from hair follicles, secretes oil onto hairs in hair follicles, micute of fats, cholesterol, proteins and salts

sebaceous glands

Functions: softens hair and skin, reduces water evaporation, bacterial

sebaceous glands


functions" protects from sunlight, heat loss, particles and insects

hair is distributed over the enitre skin surface expect palms, soles, lips, nipples and portions of external genitalia


hair is filamentous strands composed of

dead, hard keratinized cells produced by hair follicles

hair shaft

above epidermis

hair root

in epidermis and dermishollow tube that holds hair


central core of large cells and air spaces


thickest layer,keratinized pigmented flattened cells- surrounds medulla

cuticle of hair

single outer layer of keratinized cells that overlap each other- surrounds cortex

hair follicle

extends from epidermal surface into dermis- lining of hair shaft

connective tissue root sheath

dermis-blue exterior area on outer follicle wall

glassy membrane

thickened basement membrane- dark blue membrane between CT root sneath and external epithelial root sheath

external epithelial root sheath

tissue after the glassy membrane

internal root sheath

tissue after external epithelial root sheath before cuticle

hair bulb

expanded deep end, enlarged base of follicle-bottom of follicle directly under root

hair papilla of hair bulb

connective tissue with many blood vessels

hair matrix of hair bulb

ring of actively didving cells

sebaceous glands are with each hair


hair follicle receptor

sensory nerve endings around each hair bulb, stimulated by bending a hair

arrector pili muscle

smooth muscle that runs from connective tissue root sheath to suferficial dermis- contracts hair vertically

cause goose bumps, decreases heat loss by increasing the dead air space above skin, induced by stimuli

arrector pili muscle

hair growth

2 cycles growth phase and resting phase

lasts 6-10 years in scalp, 3-4 months in eyebrows

growth phase

last 1-3 months

resting phase


pale, fine body hair of children and adult femals


coarse, long hair of eyebrows, scalp, axillary and pubic regions


excessive hairiness in women due to abnormal secretion of androgens

hair pigments

melanins in medulla and cortex

dark hair

true melanin

blonde and red hair

melanin variants with iron and sulfur

gray/white hair

decreased melanain production, increased air bubble in shaft


hair thining in both sexes after age of 40

frank(true) baldness

genetically determind and sex-influenced condition


scalelike modification of epidermis on distal dorsal surface of fingers and toes

nail body

pink due to blood underlying capillaries


white cresent shape at bottom of nail

free edge

white edge of nail

nail root

anchored in skin


thick stratum corneum

Chemical Barrier

low pH secretions(acid mantle) and defensisn retard bacterial activity

melanin provides a chemical pigment to prevent UV damage to the viable skin cells


physical/mechanical barriers

keratin and glycolipids block most water and water-soluble substances

The most abundant cells of the epidermis.


The protein found in the epidermis that is responsible for toughening the skin


Cells plus a disc-like sensory nerve ending that functions as a sensory receptor for touch

Merkel disc

Skin macrophages that help activate the immune system

Epidermal dendritic cells

Cell remnants of the stratum corneum

Cornified keratinocytes

The layer of the epidermis where the cells are considered protective but nonviable

Stratum corneum

The glands that serve an important function in thermoregulation

Sudoriferous glands

The layer that contains the mitotic viable cells of the epidermis

Stratum basale

Hair that lacks pigment and is often called "immature hair."


May indicate embarrassment, fever, hypertension, inflammation, or allergy.


May indicate fear, anger, anemia, or low blood pressure


Usually indicates a liver disorder


Appearance of a permanent tan; bronzing.

addisons disease

A bluish color in light-skinned individuals


The apocrine sweat glands are fairly unimportant in thermoregulation


Skin surface markings that reflect points of tight dermal attachment to underlying tissues are
called epidermal ridges


The dense fibrous connective tissue portion of the skin is located in the reticular region of the


The outermost sheath of a hair follicle is the connective tissue root sheath


The protein found in large amounts in the outermost layer of epidermal cells is collagen.


Joe just burned himself on a hot pot. A blister forms and the burn is painful. Joe's burn would
best be described as a third-degree burn


Destruction of the matrix of the hair bulb would result in its inability to produce oil


The hyponychium is commonly called the cuticle


The reason that the nail bed appears pink is the presence of a large number of melanocytes in
the underlying dermis


During the resting phase of hair growth, the matrix is inactive and the follicle atrophies.


The most dangerous skin cancer is cancer of the melanocytes.


The skin is not able to receive stimuli because the cells of the epidermis are not living and therefore there are no sensory receptors in the skin


The dermis is rich in blood vessels and nerve fibers.


The hypodermis is composed of adipose and dense connective tissue


A physician is often able to detect homeostatic imbalances in the body by observing changes in the skin color


When an individual is exposed to extremely low air temperatures, the dermal blood vessels will dilate so that blood and heat will be dissipated.


Regardless of race, all human beings have about the same number of melanocytes


Ceruminous glands are modified merocrine glands


The stratum corneum (outermost layer of skin) is a zone of approximately four layers of viable cells that are able to synthesize proteins that keep the outer layer of skin smooth and soft


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