Chapter 12 - Skin: The Integumentary System

integumentary system

made up of the skin and its related stuctures

skin

forms the protective outer layer covering the external surfaces of the entire body

functions of the skin

-skin waterproofs the body and prevents fluid loss
-unbroken skin protects immune system by blocking entrance of pathogens
-major receptor for the sense of touch
-helps body synthesize vitamin D (from sun)
-protects from harmful ultraviolet radiation (from sun)
- largest bodily organ

sweat glands

-help regulate body temperature and water content by secreting sweat
-apocrine and eccrine glands

skin's three layers

epidermis, dermis, subcutaneous layers

cutaneous

pertaining to the skin

epidermis

-the outermost layer of skin
-made up of several specialized epithelial tissues

epithelial tissue

form a protective covering for all internal and external surfaces of body

squamous epithelial tissue

-forms upper layer of epidermis
-flat, scaly cells that shed

basal layer

-lowest layer of epidermis
-new cells are produced here and pushed upwards
-when cells reach surface, they die and become filled with keratin

keratin

-fibrous, water-repellent protein
-soft keratin is primary component of epidermis
-hard keratin found in hair and nails

melanocytes

-special cells found in basal layer
-produce and contain dark brown/black pigment (melanin)

melanin

-pigment that determines the color of the skin based on amount of pigment present
-protects skin against UV rays

dermis

-aka corium
- thick layer of living tissue below epidermis
-contains connective tissue, blood and lymph vessels, nerve fibers
- hair follicles, sebaceous glands, sweat glands

sensory nerve endings

in dermis, are sensory receptors for stimuli (touch, temp, pain, pressure)

collagen

tough, flexible fibrous protein material found in skin and in bones, cartilage, tendons, ligaments

mast cells

-found in connective tissue of dermis
-respond to injury, infection, or allergy by producing and release substances (heparin, histamine)

heparin

-released in response to an injury
- anticoagulant (prevents blood clotting)

histamine

-released in response to allergens
-causes signs of allergic response

subcutaneous layer (SC, subq)

-located below the skin and connects skin to surface muscles
-made of connective and adipose tissue

adipose tissue

fat tissue

cellulite

deposits of dimpled fat around buttocks and thighs

lipocytes

-fat cells
-manufacture and store large quantities of fat

sebaceous glands

-located in dermis
-associated with hair follicles
-secrete sebum

sebum

-oily substance that is released through ducts into hair follicles then onto skin surface and lubricates skin
-discourages bacteria growth on skin

apocrine glands

found at hair follicles

eccrine glands

-open onto skin
-palms of hand, soles of feet, forehead

pores

openings on the surface of skin

perspiration

-aka sweat
-secreted by sweat glands
-99% water + salt and metabolic waste
-up to one quart of liquid is perspired daily
-cools the body

hidrosis

production and excretion of perspiration

mammary glands

-milk producing glands
-modified sweat glands
-sometimes classified with integumentary system, but mainly part of reproductive system

hair

-helps control loss of body heat
-rod like structures composed of tightly fused, dead protein cells with hard keratin
-darkness determined by amount and type of melanin produced

hair follicles

sacs that hold the root of hair fibers

arrector pili

-tiny muscle fibers attached to hair follicles that cause hair to stand up
-response to cold or fright
-cause goosebumps

unguis

-aka fingernail/toenail
-keratin plate that protects dorsal surface of last bone in fingers/toes

parts of nail

nail plate
nail bed
free edge
lunula
cuticle
nail root

nail body (plate)

translucent, molded to surface of underlying tissues
-hard keratin epidermal cells

nail bed

-joins nail body to underlying connective tissue
-nourishes nail

free edge

portion of nail not attached to nail bed

lunula

-pale half moon-shaped region at nail root
-active area of nail where new keratin cells form

cuticle

narrow band of epidermis attached to surface of nail by root
-protects new keratin cells as they form

nail root

fastens nail to finger/toe

dermatologist

physician who specializes in diagnosing and treating disorders of skin

plastic surgeon

physician who specializes in surgical restoration and reconstruction of body structures

cosmetic surgeon

-plastic surgeons who perform operations that are usually done for aesthetic not medical reasons
-ex: breast augmentation, liposuction, facelifts

acne vulgaris

-aka acne
-chronic inflammatory disease
-pustular eruptions of skin caused by overproduction of sebum
-triggered by hormones in puberty/adolescence

comedo

-non-infected lesion formed by buildup of sebum and keratin in hair follicle
-whitehead (closed comedo)
-blackhead (open comedo)

epidermoid cyst

-aka sebaceous cyst
-closed sac that is found under skin
-contain yellow, fatty material

seborrhea

overactivity of sebaceous glands that results in production of excess amounts of sebum

seborrheic dermatitis

-inflammation sometimes resulting from seborrhea that causes scaling and itching of the upper layer of skin
-ex: dandruff

seborrheic keratosis

benign skin growth that has a waxy look

anhidrosis

abnormal condition of lacking sweat in response to heat

diaphroesis

profuse sweating

heat rash

-aka prickly heat
-intensely itchy rash caused by blockage of sweat glands

hyperhidrosis

excess sweating in one area or over the whole body

sleep hyperhidrosis

-aka night sweats
-excess sweating during sleep

folliculitis

inflammation of hair follicles

trichomycosis axillaris

superficial bacterial infection of hair shafts in areas with extensive sweat glands

hirsutism

excessive body and facial hair in women

alopecia

-aka baldness
-partial or complete loss of hair, most commonly on the scalp
-patchy

alopecia areata

autoimmune disorder that attacks hair follicles causing well defined bald areas on scalp or body

alopecia totalis

loss of all hair on the scalp

alopecia universalis (AU)

total loss of hair on all parts of body

androgenic alopecia

-most common type of hair loss
-in men: male pattern baldness, receding hairline
-in women: female pattern baldness, hair thinning

clubbing

abnormal curving of nails often accompanied by enlargement of fingertips

koilonychia

-aka spoon nail
-malformation of nails where outer surface is concave/scooped

onychia

-aka onychitis
-inflammation of bed of nail that often results in nail loss

onychocryptosis

-aka ingrown toenail
-edge of toenail curve inward and cut into skin
-results in inflammation or infection

onychomycosis

fungal infection of nail

paronychia

acute or chronic infection of skin fold around nail

Onycholysis

-separation of the nail plate from the nail bed
-nail loss

acanthosis nigricans

one of more area of skin develop dark, wart-like patches

age spots

-aka solar lentigines or liver spots
-discolorations caused by sun exposure

albinism

-genetic condition
-deficiency or absence of pigment in skin, hair, irises of eyes

chloasma

-aka melasma or mask of pregnancy
-brownish spots on the face
-can occur during pregnancy

vitiligo

-results from destruction of melanocytes due to unknown causes
-causes irregular patches of white skin

contusion

-injury to underlying tissues without breaking skin
-accumulation of blood within skin
-characterized by discoloration and pain

ecchymosis

-aka bruise
-large, irregular area of purplish discoloration due to bleeding under the skin

purpura

appearance of multiple purple discolorations on skin caused by bleeding underneath skin

petechiae

very small, pinpoint hemorrhages that are less than 2 mm in diameter

hematoma

-caused by injury
-swelling of clotted blood trapped in tissues
-often named for area where it occurs

lesion

pathologic change of tissues due to disease or injury

crust

-aka scab
-collection of dried serum/cellular debris

erosion

wearing away of surface

macule

-aka macula
-discolored flat spot that is less than 1 cm in diameter
-ex:freckles

nodule

solid, raised skin lesion that is larger than 0.5 cm in diameter

papule

small, raised red lesion that is less than 0.5 cm in diameter

plaque

scaly, solid raised area of closely spaced papules

scales

flakes or dry patches made of excess dead epidermal cells

verrucae

-aka warts
-small, heard skin lesions

wheal

-aka welt
-small bump that itches

abscess

closed pocket containing pus that is caused by bacterial infection

purulent

producing or containing pus

exudate

fluid, such as pus, that leaks out of infected wound

cyst

abnormal sac containing gas, fluid, or semisolid material

pustule

-aka pimple
-small, circumscribed lesion containing pus

vesicle

small blister, less than 0.5 cm in diameter, containing watery fluid

bulla

large blister that is usually more than 0.5 cm in diameter

abrasion

injury which superficial layers of skin are scraped or rubbed away

fissure

groove or crack-like break in the skin