ANATOMY & PHYSIOLOGY OF
THE INTEGUMENTARY SYSTEM
ANATOMY & PHYSIOLOGY 13-14
Artificial Heart
Artificial Ear
Artificial Nose
Artificial Eye
WHY HAS ARTIFICIAL SKIN BEEN SO DIFFICULT TO CREATE?
Electronic Nanoskin?
Forms and Functions Of The Integumentary System
FORMS
FUNCTIONS
• Skin
• Hair
• Scales
• Nails
• Hooves
• Feathers
• Protection
• Waterproofing
• Excretion of Wastes
• Thermoregulation
• Vitamin Synthesis
• Attachment For Sensory Structures
Histology of Integumentary System
• Epithelium
• Squamous
• Cuboidal
• Columnar
• Visceral Muscle (i.e. arrector pili)
• Follicular (i.e. hair)
• Glandular Tissue (apocrine, eccrine, sebaceous)
• Nervous Tissue
SKIN BY THE NUMBERS
• Largest organ in body
• 1-2 m2 surface area
• 12-15% of body mass
• 30,000 skin cells lost/min
• Skin cycles every 28 days
• Varying Thickness & Elasticity
• 0.02-0.6mm (eyelids)
• 1.4-3 mm (sole of foot)
STRATIFICATION OF SKIN
Epidermis
• Outermost layer of skin
• Derived from ectoderm during
cellular differentiation
• Comprised of squamous epithelium
(~95% keratinocytes)
• Avascular
• Protects the organism (pH 5/dry)
• Regulates water loss via
Transepidermal Water Loss (TEWL)
Epidermal Histology
• Stratum Corneum = 10-30 layers of
corneocytes (thickest in palms and soles).
Barrier function
• Stratum Lucidum = 4-5 cells thick (only in
palms and soles)
• Stratum Granulosum = anucleate, fatty layer
• Stratum Spinosum = Interconnected
keratinocytes with immunological functions
• Stratum Basale = Contains melanocytes and
Merkel Cells (light touch)
Melanocytes
• Melanin producing cells of Stratum Basale
• 1000-2000 cells/mm2
• Skin color attributed to activity of
melanocytes, NOT their density
• Human skin color takes up to 6 months to
fully develop
• Two types of melanin
• Pheomelanin = yellow->red
• Eumelanin = brown->black
• Melanin protects against UV radiation.
• UV damage to DNA stimulates melanogenesis
Albinism/Achromasia
• 1:110,000 humans lacks the
enzyme tyrosinase
• Recessive condition
• Tyrosinase required for
melanogenesis
• Two forms
• Oculocutaneous = eye and skin
• Ocular = eye only
Fingernails
•Epidermal
extension
•Nail Plate
(non-living)
•Nail Bed (living)
•Lunula
Dermis
• Layer between epidermis and subcutaneous
• Made of connective tissues (collagen & elastic fibers)
and cells (fibroblasts, macrophages & adipocytes)
• Vascular
• Two Dermal Regions
• Stratum Papillare (bordering epidermis)
• Blood vessels
• Meissner’s Corpuscles
• Stratum Reticulare (deep)
• Follicular Roots
• Sebaceous Glands
• Apocrine & Eccrine Glands
Folliculus pili
• Comprised of epithelial cells, visceral muscle
and adjacent sebaceous glands
• Activity of Folliculus pili
• Anagen = 1cm growth/28 days for 2-7 years
• Catagen = 2-3 weeks where hair is cut off
from blood supply and forms a “club” end
• Telogen = 3 months. Hair at rest. Stress
may cause 70% of hair to enter telogen
• Exogen – loss of hairs (20-100 day)
Arrector pili
• Visceral muscle connected to
club/base of hair shaft
• Autonomic control via
sympathetic nervous system
• Causes erection of hair shaft
(piloerection)
• In many species, piloerection
allows for retention of heat
• Function in humans is
vestigial
Sebaceous Glands
• Apocrine Gland = expressed when cells rupture
• Most common in scalp and face, part of
pilosebaceous unit along with hair shaft and
arrector pili
• Sebum = Fatty mixture of waxes, triglyceride oils
and fatty ester
• Keep hair shaft flexible, antibacterial and slows
evaporation
• Vernix caseosa = white sebaceous layer on
newborns.
• Food source for Demodex mites
Sudoriferous Glands
• Two types
• Eccrine = distributed all over body
• Apocrine = concentrated in armpits, anus
• Produce sweat; a mixture of water, salt, urea
and vitamin C
• Essential homeostatic structures utilized for
thermoregulation and antibacterial properties
• Only areas that do not sweat are fingernails,
eardrums, lip margins and glans
• Other modified sweat glands include
• Ceruminous = ear wax
• Ciliary = eyelids
• Mammary = milk
Dermal Papillae and Friction Ridges
• “fingerprints”
• Genetically determined but do not
develop until 3rd gestational month
• Derived from the dermal papillae,
replaced when eroded
• Basis of dactyloscopy
• Naegeli Syndrome = no fingerprints!
Hypodermis/Subcutaneous Layer
• Lowest of all skin layers
• Derived from mesoderm
(not ectoderm)
• Contents
• Adipose
• Vascular and Lymphatic Tissue
• Ruffini and Pacinian
Corpuscles (sensory)