Integument Flashcards
Integument
barrier for protection, sensation, excretion, thermoregulation, and synthesis of Vitamin D3
composed of epidermis and dermis
epidermis=ectoderm
dermis=mesoderm
Hypodermis
a loose CT layer that binds skin to underlying tissues and corresponds to the superficial fascia
Epidermis
stratified squamous keratinized epithelium composed of keratinocytes
-also contains melanocytes, langerhans cells, and merkel cells
Dermal papillae
irregular projections at epidermal-dermal junction
has epidermal ridges to strengthen adhesion
Thick skin
palms and soles
has five layers
fingerprints
Thin skin
widespread on body
four layers
glands and hair follicles
THe layers of the epidermis
Stratum corneum stratum lucidum stratum granulosum stratum spinosum stratum basale
Keratinocytes
predominant cell typer of the epidermis
makes keratin
participate in the epidermal water barrier
cornified cells that undergo keratinization and desquamation
Strtum basale
single layer of keratinocytes with some stem cells
mitotically active, cuboidal and low columnar cells
contain melanin
bound apically via demosomes
bound basally by hemidesmosomes
Stratum spinosum
The thickest layer
polyhedral cells with central nuclei and spiny processes
keratin filaments assemble here into microscopically visable bundles called tonofibrils
Stratum Granulosum
three to five layers of flattened cells
filled with keratohyaline granules
these stain intensely basophilic
lamellar granules which are small ovoid structures containing lipids and glycolipids which will exocytosis and produce lipid rich impermeable layer that protects against water lass
keratinization and lipid rich layer make up an almost impentetrable skin barrier
Stratum corneum
15-20 layers of squamous keratinized cells filled with filamentous keratins
anucleate and coated by an extracellular layer of lipids
fully keratinized cornified cells squames
Stratum Lucidum
found only in thick skin
thin translucent layer of flattened eosinophilic keratinocytes
nuclei and organelles haave been lost
cytoplasm is almost exclusively keratin filaments
Melanocytes
produce melanin and transfers it to keratinocytes
melanin=pigment protein that protects nuclei from UV radiation
neural crest derived
Epidermal-melanin unit
one melanocyte maintains an association with a specific number of keratinocytes (1:10)
Melanin production
Tyrosinase converts tyrosine to DOPA and that is polymerized to produce melanin
this occurs in membrane bound organelles called premelanosome
as the melanin increases the premelanosome will turn into melanosome which will be transfered to keratinocytes as a pigment donation
Langerhans cells
Antigen presenting cells
develop from monocyte
found in the stratum spinosum
Epidermal differentiation and replacement
cell replacement is initiated by the division of stem cells in the stratum basale
then they move upward where they differentiate into keratinized cells
eventually are lost by exfoliation on skin surface
Dermal-epidermal junction
uneven boundary with finger like dermal papillae that project into the epidermis
complemented by epidermal protrusions, epidermal ridges
Layers of the Dermis
Papillary layer
Reticular layer
Papillary layer
loose CT immediately beneath epidermis
Vasculature and nerve endings
Reticular layer
Deep to papillary layer
Dense irregular CT with coarse elastic fibers
form regular lines of tension-Langers lines
Subpapillary plexus
rich nutritive capillary network located btwn papillary and reticular layers
Deep plexus
Lies near Dermis subcutaneous layer interface
Hypodermis
Subcutaneous fascia
loose CT that binds the skin loosely to the subjacent organs
adipocytes vary in number and size based on body regions and nutritional state
extensive vasculature promotes rapid uptake or insulin or drugs injected into the tissue
what type of sensory receptors does skin have
non encapsulated and encapsulated receptors
Merkel Cells
Epithelial tactile cells that function as low threshold mechanoreceptors essential for sensing touch
similar look to keratinocytes but lack melanosomes
contain small golgi derived granules concentrated near basolateral surface
Merkel cell carcinoma
rare aggressive and difficult to treat
40 times less common than malignant melanoma
but double the mortality rate
Free Nerve endings
located in the papillary dermis and extending into the lower epidermal layers
respond primarily to high abd low temperatures, pain and itching
serve as tactile receptors
Meissners Corpuscle
encapsulated receptors responsive to light touch or low frequency stimuli
Perpendicular to the epidermis in the dermal papillar
numerous in the fingerprints and soles
Lamellated Pacinian Corpuscle
Large encapsulated oval structures found deep in the reticular dermis and hypodermis
specialized for sensing coarse touch, pressure (sustained touch) and vibration
found in CT of visceral organs
wall of the rectum and urinary bladder
produce pressure sensations when distorted
Sebaceous glands
several glands per follicle
abundant on face and scalp
produce a lipid mixture sebum via holocrine secretion
waxy mix of triglycerides and cholesterol
lubercates and softens the skin
sebum discharges into the hair follicle
Eccrine Sweat glands
simple coiled glands found throughout the skin
duct is stratified cuboidal
Myoepithelial cells facilitate expulsion of secretions
temperature regulation via cooling
Apocrine sweat glands
large lumen tubular glands
duct is stratified cuboidal
merocrine secretion
- protein carbohydrate and ammonia rich secretion
- odorless until mixed with bacteria
become functional at puberty
Hair follice
terminal dilation called a hair bulb
dermal papilla inserts into hair bulb to provide nutrients
keratinocytes form the hair matrix
-are continuous w/epidermis
Follicular bulge: contains epidermal stem cells
Arrector pili muscle
small bundle of smooth muscle that extends from the midpoint of hair to papillary layer
contraction of these form the goose bumbs and distorts the dermis
Nails
Nail root
Nail matrix: divide and form the keratinocytes
-pushed forward with continous growth
Lunula: crescent shaped white area near the nail matrix
cuticle: extension of skin covering the nail root
