chapter 6: the integumentary system

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96 Terms

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skin is the body’s
largest organ (\~20 lbs)
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dermatology
the study of the integument (skin)
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the integumentary system is made up of
* integument (skin)
* accessory organs (hair, nails, cutaneous glands)
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this system is the most
noticeable organ system and it can also show symptoms from various diseases of other organ systems
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skin
* largest/heaviest organ
* made up of two parts:

\------epidermis (epithelium) & dermis (L areolar CT; D irregular CT)
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the hypodermis is not part of the skin but it is made of
* areolar CT and adipose tissue
* regions of predominately adipose tissue which are subcutaneous fat
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skin is classified as thick or thin based on the
thickness of the epidermis alone
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thick skin
* found on palms, soles, and corresponding surfaces on fingers and toes

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* lacks hair follicles and sebaceous glands but has sweat glands
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thin skin
* covers everything of the body that the thick skin doesn’t cover

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* contains hair follicles, sweat, and sebaceous glands
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functions of the skin
* contains the body
* resists trauma and infection
* serves as a barrier to water loss/gain, UV radiation, and certain chemicals
* vitamin D synthesis
* sensation
* thermoregulation
* nonverbal communication
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resist trauma and infection
* keratin, abundant desmosomes, and a dry slightly acid mantle surface (pH 4-6)
* also certain defensive molecules are present (dermicidin and defensins)
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sensation
nerves not uniform in distribution

* more abundant in face, palms, fingers, soles, nipples, and genitalia

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multiple sensations originate from receptors in the skin

* hot, cold, touch, texture, pressure, vibration, pain
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thermoregulation
via cutaneous vasoconstriction and vasodilation
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keratinized epithelium
found in epidermis and covered with a layer of dead compressed cells (keratinocytes)
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nonkeratinized epithelium
lacks the dead layer of cells (keratinocytes)
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a closer look at epidermis
* lacks blood vessels and relies on diffusion of nutrients from underlying CT (dermis)
* some nerve endings for touch and pain
* many cell types present


1. stem cells - unipotent
2. keratinocytes
3. melanocytes
4. tactile cells
5. dendritic cells
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stratum basale (deepest layer)
simple cuboidal/columnar stem cells, melanocytes, keratinocytes
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stratum spinosum
layers of keratinocytes; deep cells make more keratinocytes through mitosis---superficial cells make keratin
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stratum granulosum
3-5 layers of keratinocytes, flat layers, and organelles are deteriorating
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stratum lucidum
only in thick skin; keratinocytes have no organelles; cells are packed together with eleidin (protein)
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stratum corneum
made of dead cells (up to 30 layers) that are highly keratinized

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resists abrasion, penetration, and water loss
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stem cells - epidermis
undifferentiated cells that give rise to keratinocytes in the stratum basal
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keratinocytes - epidermis
major cell; responsible for making keratin
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melanocytes - epidermis
make melanin; cells remain in the stratum basale

* packages of melanin (melanosomes) are exocytosed and absorbed by nearby keratinocytes
* melanin protects the nucleus of the keratinocyte from UV radiation
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tactile cells - epidermis
involved in sensation of touch; tactile discs include the cell and associated nerve endings
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dendritic cells - epidermis
immune cells that have migrated to the stratum spinosum or stratum granulosum
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life history of keratinocytes in stratum basal
* begins with differentiation from stem cells

(process can be sped up/intensified by constant abrasion leading to a production of a thicker epidermis- callus or corn)

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* pushed towards the surface and the cells of the stratum spinosum rarely divide; rather accumulate as pre-keratin molecules
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life history of keratinocyte in stratum granulosum
* keratinocytes flatten and increase keratin (protection) and lipid production
* cell surface is waterproofed by releasing lipid mixture
* cells die
* in conjunction with tight junctions, an epidermal water barrier is created
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life history of keratinocyte in stratum corneum
* sloughed off as dander through exfoliation
* dandruff is clumps of dander held together by sebum
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dermis
* made primarily of collagen but has elastic and reticular fibers along with cells typical of CT
* HIGHLY vascular
* contains many cutaneous glands and nerve endings
* LOCATION NOT ORIGIN of hair follicles and nail roots
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papillary region of the dermis
superficial; areolar CT

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* conspicuous dermal papilla and epidermal ridges
* produces friction ridges that lead to finger prints
* exceptionally tall dermal papillae in highly sensitive areas to allow nerve endings to reach closer to the surface
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reticular layer of dermis
deep; dense irregular CT

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* striae (stretch marks) occur because of fibrosis occurring in this region
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three pigments contribute to skin color
* **melanin (melanocytes)**-----only pigment made in skin

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* **carotene (stratum corneum)**---------------------from plant products, accumulates in corneum and fatty deposits of the hypothermis, converts to vitamin A; good for epidermal health

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* **hemoglobin (blood vessels)**------ pinkish color; more evident in lighter skin
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pheomelanin
reddish yellow
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eumelanin
brownish black
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melanin
* produced in melanocytes
* color difference of skin is due to the amount and form of melanin ------lighter skin = larger clumps & dark skin = smaller clumps
* melanin migrates to keratinocytes to form “pigment shields” for nuclei (UV protection)
* freckles and pigmented moles are accumulations of melanin
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cyanosis
blue skin color- low oxygenation of hemoglobin
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erythema (redness)
fever, hypertension, inflammation, allergy
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pallor (blanching)
anemia, low blood pressure, fear, anger
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jaundice (yellow cast)
liver disorder
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hematoma (bruises)
clotted blood beneath the skin
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albinism
* genetic mutation disorder
* melanocytes don’t make melanin
* skin is pink, hair white, irises unpigmented
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friction ridges
* fingertips, soles of feet
* enhance sense of touch and grip
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flexion lines (flexion creases)
* dermal folds at/near joints
* dermis tightly secured to deeper structures
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hemangiomas (birthmarks)
* benign tumors of the capillaries
* capillary hemangiomas or cavernous hemangiomas-- present at or soon after birth, often disappear with age
* port-wine stain-- flat, pinkish to dark color in color; remain for life
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accessory organs of the integumentary system
hair, nails, and cutaneous glands

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hair and nails- made primarily of dead, keratinized epidermal cells (hard keratin)
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hair (pili)
all over the body except palms, soles, nipples, and parts of the external genitalia
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functions of hair (pili)
* sensation of insects and parasites on the skin
* head hair helps retain heat, protect the scalp from UV radiation
* beard and axillary and pubic hair signify sexual maturity and may aid in transmission of sexual scents
* guard hairs (vibrissae) protect the eyes, nasal cavity, and ears from debris
* eyebrows may protect eyes from sweat and is also important in facial expressions
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lanugo (no pigment)
fine hairs on the fetus during last trimester
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vellus (some pigment)
replaces lanugo hair; remains dominant on women and makes up 2/3 of their body hair, 1/10 on men, and all the hair on children except for the terminal hair
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terminal hair (heavily pigmented)
makes up the hair on the scalp, eyebrows, and eyelashes; after puberty it makes up the hair of the axilla, pubic region, male facial hair, some of the hair on trunk and limbs
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hair shaft
sticks out from skin
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hair root
part of the hair in the follicle
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layer of keratinized cell- cuticle
heavily keratinized; arranged like overlapping shingles
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layer of keratinized cell-cortex
hard keratin with injected melanin, flattened
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layer of keratinized cell-medulla
large cells and air spaces
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what is the follicle?
a tube of epidermial (epithelial) in the dermis
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hair bulge
contains stem cells for follicle growth and capillaries for blood supply
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hair receptors
nerve fibers that detect hair movement
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pilorector muscles
AKA arrector pili or pilomotor muscles

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\-smooth muscle to raise hairs. (goosebumps)

\-hair matrix---- mitotically active cells- hair growth
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cross sectional hair shapes
straight = round

wavy = oval

curled = flat
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hair color due to pigment
brown/black = rich in eumelanin

red= rich in pheomelanin, some eumelanin

blond= little eumelanin and some phemomelanin

gray= little melanin; airspace in the medulla
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alopecia
\-thinning of the hair

influenced by nutritional and other health factors
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pattern baldness
\-genetic and hormonal

in males = dominant trait influenced by testosterone

in females = recessive trait influenced by testosterone
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hirsutism
\-undesireable hair growth (especially in women and children)

influenced by abnormal testosterone levels and genetics
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nails
* hardened derivative of the stratum corneum
* made of thin, dead keratinocytes with parallel-arranged hard keratin fibers
* changes in nail appearance can indicate


1. yellowing nails---respiratory or thyroid gland disorders
2. concavity of nail (spoon nail)---- iron deficiency
3. horizontal lines (beau’s lines)----malnutrition
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free edge
extends beyond distal edge of fingertip
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nail body
visible attached portion
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nail root
proximal edge of nail embedded in skin
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nail bed
epidermal layers deep to nail body
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nail matrix
thickened proximal portion of nail bed --- makes the nail cells which become keratinized as the nail body grows distally
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sudoriferous (sweat) glands
apocrine sweat glands (also merocrine)

merocrine (eccrine) sweat glands
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sebaceous glands
oil glands; secrete sebum; utilize holocrine secretion method; important for normal hair and skin health
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ceruminous glands
only in external ear; secretions combine with sebum to make ear wax (cerumen); important to keep eardrum pliable; waterproof canal; kill bacteria; block foreign particles
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mammary glands
secrete breast milk
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apocrine sweat glands
* confined to axillary (armpit), areolar (nipple), and genital areas: beards of adult males
* secretions (INTO hair follicle) contain fatty acids and proteins
* secretion is odorless
* begin functioning during puberty (androgen influenced)
* activated by nerve fibers during pain, stress, and sexual activity
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merocrine sweat glands
* **secrete to skin surface**
* **acidic secretion -**-- primarily made of water (99%), some NaCl, vitamin C, some waste products (ammonia, urea, uric acid) , lactic acid
* creates acid mantle (pH 4-6) = inhibits bacteria
* widely distributed on body--- palms, soles, forehead
* primarily responsible for cooling the body
* evaporative cooling (water has high specific heat- hydrogen bonds)
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myoepithelial cells
push perspiration up the duct
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insensible perspiration
occurs constantly \~500 mL day
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diaphoresis
sweat that is noticeable caused by heat and exercise
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acne
Inflammation of sebaceous glands, follicle blocked with keratinocytes and Sebum, develops ​into a whitehead composed of these and bacteria; more inflammation results in pus (pimple)
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dermatitis
Any inflammation of the skin, usually with itching and redness; (e.g. poison ivy/oak)
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eczema
Itchy, red, “weeping” skin lesions caused by an allergy, may progress to thickened, leathery, dark patches
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psoriasis
Recurring, reddened plaques covered with silvery scale; possibly caused by an autoimmune response; hereditary
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rosacea
A rashlike formation, often around nose and cheeks, marked by fine networks of dilated blood vessels; worsened by hot drinks, alcohol, and spicy food.
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seborrheic dermatitis
Patches of scaly white or yellowish inflammation often on head, face, chest, back; called *crɑdle cɑp*​

(a yellow, crusty scalp lesion) in infants. Cause unknown, but related to genetic and climatic factors.
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tinea
Any fungal infection of the skin; common in moist areas such as the axilla, groin, and foot *(ɑthlete’s foot)*. E.g. ringworm
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skin cancer
uncontrolled division of skin cells, most are benign, others are malignant

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most important risk factors are exposure to UV radiation and genetics
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mole
uniform color, even contour, relatively small
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cancer
various color, scalloped border, large and spreading
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basal cell carcinoma
least malignant; most common;  cells of stratum basale proliferate and invade dermis and subcutaneous layers
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squamous cell carcinoma
Cells of stratum spinosum; believed to be sun-induced (head and hands). Not so bad unless – metastasizes to nearby lymph nodes
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malignant melanoma
cancer of the melanocytes; accounts for only 5% of skin cancers but is often deadly​

* Does not respond to chemotherapy ​
* Average lifespan- 6 months ​
* Greatest risk factor is family history 
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first degree burn
partial thickness burn

* epidermis damaged only
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second degree
partial thickness burn

* blistering occurs (fibrosis possible = scar tissue)
* upper regions of dermis damaged
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third degree
full thickness burn

* epidermis, dermis, hypodermis, and underlying tissue (muscle/bone)
* requires skin grafts
* no regeneration of skin