Integumentary System Flashcards
skin (cutaneous membrane)
epidermis (epithelium)
dermis (connective tissue
accessory structures
exocrine glands
hair
nails
major functions
physical + immunological protection
thermoregulation
sensation
metabolic functions
- vit D synthesis
- energy storage as subcutaneous fat
tissue composition
all four tissue types are present in integument
- epithelium
- connective tissue
- muscle (smooth)
- nerve
epithelium
epidermis
covers surface
forms boundary → epidermis is continuous with epithelium lining internal structures
connective tissue
dermis
supports epithelium
provides strength + resiliency
muscle
smooth muscle
arrector pili muscles adjust hair position (stretch up in cold)
controls diameter of blood vessels (vasodilation/constriction in hot/cold)
nerve
controls smooth muscle
generates sensation → junction between epidermis + dermis (tactile, pressure, temp, etc)
stimulates exocrine glands
characteristics of skin
epidermis + dermis
largest organ system of body (about 15% of total body mass)
covers 2 m^2
ranges in thickness depending on area of body
- avg 1-2mm
- eyelids ~0.5mm
- heel ~4.0mm
interface between dermis + epidermis
epidermal ridge
dermal papilla
interlocking of layers
allows for tight bond between layers of skin → resist shearing stresses
epidermis
deep → superficial
- stratum germinativum
- stratum spinosum
- stratum granulosum
- stratum lucidum
- stratum corneum
stratified squamous epithelium
keratinocytes
most abundant epithelial cells in epidermis
basal cells
stem cells that divide to give rise to new keratinocytes
stratum germinativum
= stratum basale
base of epidermis
composed of large basal cells
firmly attached to basal lamina = epidermal ridge
stratum spinosum
“spiny layer”
composed of keratinocytes → contain bundles of tonofilaments
keratinocytes still capable of division
tonofilaments
protein filaments
‘spines’
run through cells to margin
act as cross braces → begin + end between adjacent cell junctions
desmosomes
cell junctions
attach keratinocytes together
stratum granulosum
‘granular’ layer
production of large quantities of keratohyalin + keratin
keratohyalin
produced by stratum granulosum
accumulates into granules → secretes lipids that fill spaces between cells
= water-repellant sealant → prevents diffusion of nutrients across membrane = apoptosis
stratum lucidum
“clear” layer
large amounts of keratin + thickened plasma membranes = transparent
only found in volar skin → palmar/plantar
stratum corneum
corne = hard
multiple layers of dead cells - varies in thickness
cells continuously shed and are replaced
forms water repellant barrier
protection against abrasion + microbial invasion
thin skin
thinner stratum corneum
difficult to distinguish other epidermal layers
less developed dermal papillae + epidermal ridges (needs less support → less friction)
ex. eyelids
thick skin
thicker stratum corneum
clearly defined epidermal layers
developed dermal papillae + epidermal ridges
ex. heel of foot
dermis
two layers:
papillary layer
reticular layer
papillary layer
superficial dermis
adjacent to epidermis
thinner layer
made of areolar connective tissue = lots of extracellular matrix
papillae increases area of contact with epidermis
contains nerve endings → touch + pressure, temp, pain
reticular layer
thicker layer
dense, irregular connective tissue
many elastic fibers
provides extensibility + elasticity to skin = strength + resiliency
lines of tension
collagen fiber bundles in dermis align along lines of tension
align differently in different regions of body
lines of cleavage
alignment of collagen fiber bundles along lines of tension
incisions must be parallel to lines → perpendicular cuts will stay open
hypodermis
superficial fascia
not part of integument but proximal to dermis
stabilizes position of skin relative to underlying tissues = substrate for skin to rest on
loose connective tissue - stores fat
distribution of subcutaneous fat differs between sexes
influences shape + contours of body
Merkel cells
least common cell type
in stratum germinativum (deepest layer of epidermis)
involved in sensation → touch
Langerhans cells
originate from red bone marrow + migrate to epidermis
in stratum spinosum
associated with immune system → phagocytic capabilities
= immune response initiation
melanocytes
8% of epithelial cells
in stratum germinativum (along columnar cells)
produce melanin pigment → skin colour
contain long processes that insert between keratinocytes to transfer melanosomes
melanosomes
vesicles from melanocytes
granules containing melanin pigment
transferred into keratinocytes
destroyed by lysosomes as keratinocytes move superficially (persist in darker skin)
anatomy of skin colour
blood supply to dermis
thickness of stratum corneum
variable quantities of pigments:
- carotene
- pheomelanin
- melanin
carotene
yellow/orange pigment
pheomelanin
red/yellow pigment
melanin
brown/black pigment
increased rate of synthesis + transfer by melanocytes in response to UV radiation exposure
prevents DNA damage
hemoglobin in dermal blood vessels
oxygenated Hb = pink hue
deoxygenated Hb = blue (cyanosis)
vasodilation = red
UV-induced skin damage in epidermis
chromosomal damage
causes skin cancer (basal cell carcinoma)
UV-induced skin damage in dermis
damage to fibroblasts = ↓ stretching ability of elastic fibres
alters composition of extracellular matrix
= premature aging of skin; wrinkling
merocrine secretion
eccrine
secretory product is released by exocytosis
no cell death
most common mode of secretion
holocrine secretion
secretory product invades cells → burst to release product
= cell death (eventually replaced)
apocrine secretion
secretory product is released with shedding of cytoplasm of cells but no cell death
“in between” process of merocrine + holocrine
exocrine glands
sweat glands
sebaceous glands
sweat glands
merocrine secretion
secrete water + electrolytes (sweat)
simple, coiled tubular glands
two types: apocrine and merocrine sweat glands
merocrine sweat glands
secrete normal sweat
widespread
regulate body temp
apocrine sweat glands
secrete odiferous sweat (normal sweat + lipids, proteins) → acted on by bacteria = odour
specific to body regions (axilla, groin, breast areola, male facial hair)
stimulated during emotional stress + arousal
ceruminous glands
modified apocrine sweat glands
merocrine secretion
secrete waxy cerumen (ear wax)
mammary glands
modified apocrine sweat glands
apocrine secretion
specialized for milk production
regulated by interaction of sexual + pituitary hormones
sebaceous glands
holocrine secretion
secrete oily lipid (sebum) that coats hair shafts + skin surface
sebaceous follicle = open in skin
sebaceous gland = associated with hair
acne
inflammation of sebaceous glands + follicles
inflammation results from blockage of ducts + bacterial infection of glands
usually occurs at onset of puberty → glands increase in size + sebum secretion increases in response to sex hormones
hair
~ 5 million on body
2% on head → UV protection + thermal insulation
covers all body surfaces except volar skin
eyes, nose, + ears → particle filtration (eyeball, airway)
touch sensation
hair follicle
hair papilla at base = where blood vessels feed (growth)
hair bulb
hair root = inside
hair shaft = extends to surface (exposed above skin)
boundary between hair shaft + root
epidermis surrounds shaft deep into dermis
covered by connective tissue sheath
arrector pili muscle connects → sympathetic input
vellus hairs
fine hair found over most of body
intermediate hairs
on limbs
change in distribution in response to sex hormones
coarser
terminal hairs
heavier + more pigmented
scalp, eyebrows, eyelashes
hair growth cycle
scalp hair
active phase: growth; 2-6 years
regression → loosening attachment in follicle
resting phase: no growth; 3 months = club hair
new hair pushes old out
85% in growth phase
nail
distal phalanx covered by dermis, epidermis
nail bed = epidermis lining nail root + underneath nail body
lunula = matrix; visible part of nail bed
eponychium: cuticle, seals top of body
hyponychium: seals underneath nail
