CH 5: The Integumentary System

Epidermis tissue type

keratinized stratified squamous epithelium (superficial cells are dead)

Epidermis vascularity

avascular

Cells of epidermis

keratinocytes, melanocytes, dendritic cells, tactile cells

Keratinocytes FUNCTION

produce keratin (fibrous protein that help give epidermis protective properties)

Keratinocytes LOCATION

vast majority of epidermal cells (in many layers)

Melanocytes FUNCTION

epithelial cells that synthesize the pigment melanin (brown-black pigment)

Melanocytes LOCATION

stratum basale

Dendritic cells FUNCTION

immune surveillance, ingest foreign substances and key activator of immune system

Dendritic cells LOCATION

stratum spinosum, stratum granulosum

Tactile cells FUNCTION

touch receptors that are intimately associated with disclike sensory nerve ending

Tactile cells LOCATION

startum basale, epidermal-dermal junction

Layers of Epidermis - Deep to Superficial

Stratum basale (germinativum/basal layer), Stratum spinosum (prickly layer), Stratum granulosum (granular layer), Stratum lucidum (clear layer), Stratum corneum (horny layer)

Thick skin

covers areas subject to abrasion (palms, fingertips, soles of feet); has all five layers/strata

Thin skin

covers rest of body, stratum lucidum is ABSENT and other strata are thinner

Dermis vascularity

vascularized

Dermis dermal layers

papillary, reticular

Papillary layer - tissue type

areolar connective tissue

Papillary layer additional structures

dermal papillae (dermal ridges, epidermal/friction ridges) capillary loops, free nerve endings, meissner’s corpuscles

Reticular Layer - tissue type

dense irregular connective

Reticular layer additional structures

cutaneous plexus, flexure lines

Cutaneous plexus

network of dermal arteries along reticular layer

Flexure lines

dermal folds that occur at or near joints, where dermis is tightly secured to deeper structures

Hypodermis tissue type

adipose (subcutaneous fat) and areolar tissue

Hypodermis function

energy storage, thermal insulation, connection to deeper tissue

Stratum basale (germinativum/basal layer) CELLS

melanocytes, stem cells, basal cells, keratinocyte, tactil epithelial cell

Stratum basale (germinativum/basal layer)

deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of more superficial layers; occasionally see melanocytes and epidermal dendritic cells

Stratum spinosum (prickly layer) CELLS

keratinocytes, dendritic cell

Stratum spinosum (prickly layer)

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

Stratum granulosum (granular layer) CELLS

keratinocytes

Stratum granulosum (granular layer)

3-5 layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules

Stratum lucidum (clear layer) CELLS

dead keratinocytes

Stratum lucidum (clear layer)

clear, featureless, narrow zone seen ONLY IN THICK SKIN

Stratum corneum (horny layer) CELLS

anucleate cells of stratum cornea

Stratum corneum (horny layer)

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

Dermal papillae

peglike projections from its surface, indent overlying epidermis

Dermal papillae - dermal ridges

in thick skin, papillae lie atop larger mounds

Dermal papillae - epidermal/friction ridges

overlying epidermis, enhance ability to grip certain kinds of surfaces

Capillary loops

small looped blood vessels in dermal papillae to provide oxygen and nutrients to overlying epidermis

Free nerve endings

unencapsulated sensory receptor to detect pain, temperature, touch, itch by extending into epidermis and dermis

Meissner’s corpuscles

encapsulated mechanoreceptors to detect fine touch, low-frequency vibrations, slip of an object against skin; in areas like fingertips and palms

Skin color

melanin, carotene, hemoglobin

Melanin

polymer made of amino acids (tyrosine), two forms range in color from reddish yellow to brownish black

Carotene

yellow to orange pigment found in certain plant products like carrots

Hemoglobin

pinkish hue of fair skin reflecting crimson color of oxygenated pigmetn in red blood cells circulating through dermal capillaries

Hairs and hair follicles LOCATION

distributed over entire skin except palms, soles, lips, nipples, parts of external genitalia

Hairs and Hair follicles FUNCTION

sense insects on skin surface, guard head against physical trauma heat loss and sunlight, shield eyes, filter large particles like lint and insects when inhaling

Structure of Hair - Two regions

shaft, root

Hair shaft

part that projects above skin’s surface, flat and ribbon-like in cross section

Hair Root

part embedded in the skin

3 Layers of Hair

medulla, cortex, cuticle

Medulla

central core, consisting large cells and air spaces; only part of hair contain soft keratin and is absent in fine hairs

Cortex

bulky layer surrounding medulla, consist several layers of flattened cells

Cuticle

single layer of cells overlapping one another like shingles on roof; most heavily keratinized part of hair providing strength and keeping inner layers tightly compacted

Hair Follicle: Wall

peripheral connective tissue sheath (fibrous sheath), glassy membrane, external and internal epithelial root sheath

Hair Follicle: Wall - Peripheral Conective tissue sheath (fibrous sheath)

connective tissue sheath is derived from dermis; form external layer of follicle wall

Hair Follicle: Wall - Glassy membrane

at junction of fibrous sheath and epithelial root sheathl in essence, the basement membrane of follicle epithelium

Hair Follicle: Wall - Epithelial root sheath

epithelial root sheath derived from epidermis

Hair Follicle: Wall - EXTERNAL Epithelial root sheath

direct continuation of epidermis

Hair Follicle: Wall - INTERNAL Epithelial root sheath

derived from matrix cells

Hair bulb Components

hair follicle recepter (root hair plexus), hair papilla (papilla of a hair follicle), hair matrix

Hair Follicle receptor (root hair plexus)

knot of sensory nerve ending; wrap around each hair bulb

Hair papilla (papilla of a hair follicle)

dermal papilla that protrude into hair bulb; contain knot of capillaries supplying nutrient to growing hair and signal to grow

Hair Matrix

dividing cells; lies immediately adjacent to hair paella; produces new hair cells, older part of hair is pushed upward and fused cells become increasingly keratinized and die; hair matrix cells replenished by stem cells that migrate down to hair bulge

Arrector pili

bundle of smooth muscle cells associated with each hair follicle; attached in such a way that its contraction pulls hair follice upright and dimples skin surface to produce goose bumps in response to cold temperatures or fear

Hair Follicle component

wall, hair bulb, arrector pili

Types of Hair

vellus hair, terminal hair

Vellus Hair

pale and fine

Terminal Hair

coarser, longer hair of eyebrows, eyelashes, and scap (may also be darker); grow in response to stimulating effects of androgens (male sex hormone)

Nail

form clear protective covering on dorsal surface of distal part of finger or toe

Nail FUNCTION

pick small objects or scratch

Nail structures

free edge, body (nail plate), root, nail matrix, cuticle (eponychium), hyponychium

Free edge

tip/white part of the nail

Body (nail plate)

visible attached portion

Nail root

embedded in the skin

Nail matrix

thickened proximal portion of nail bed; responsible for nail growth

Cuticle (eponychium)

proximal nail fold projects onto nail body

Hyponychium

clear thickened region beneath free edge of nail where dirt and debris tend to accumulate; secures free edge of nail plate at tip of finger or toe

Sweat glands (sudoriferous glands)

distributed over entire skin surface except nipples and parts of external genitalia

Types of sweat glands

(merocrine) eccrine sweat gland, apocrine sweat gland, ceruminous gland, mammary gland

(Merocrine) Eccrine sweat gland BODY LOCATION

everywhere especially palms, soles, and forehead

(Merocrine Eccrine sweat gland INTEGUMENT LOCATION

dermis - reticular layer

(Merocrine) Eccrine sweat gland FUNCTION

produce water perspiration to cool body (contains some wastes found in urine); temperature control and some antibacterial properties

Apocrine sweat gland BODY LOCATION

groin, anal region, axilla, areola, and beard; mostly axillary and anogenital regions

Apocrine sweat gland INTEGUMENT LOCATION

dermis or subcutaneous tissue

Apocrine sweat gland FUNCTION

produce sweat with fatty acids, respond to stress and sexual stimulation, possibly secret pheromones

Cerminous gland BODY LOCATION

lining of external ear canal

Cerminous gland FUNCTION

keeps eardrum pliable, waterproofs canal, kills bacteria, and coats guard hairs with their produced sticky bitter substance cerumen (earwax)

Mammary glands BODY LOCATION

breasts

Mammary glands FUNCTION

produce/secrete milk

Sebaceous glands (oil glands)

simple branched alveolar glands

Sebaceous glands (oil glands) BODY LOCATION

all over body except thick skin of palms and soles

Sebaceous glands (oil glands) INTEGUMENT LOCATION

dermis

Sebaceous glands (oil glands) FUNCTION

produce oily secretion (sebum), holocrine secretion, keep skin and hair from becoming brittle

Functions of Integumentary system

protection (resistance to trauma and infection), body temperature regulation (thermoregulation), metabolic functions, blood reservoir, excretion