skin an integument
TRANSCRIPT
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SKINthe human integument
Dr. Zairuddin BinAbdullah Zawawi
Pakar Ortopedik
HRPZ II
Kota Bharu,Kelantan
http://ovidsp.tx.ovid.com/mms/434f4e1a73d37e8cabd934ac87c62ccfbb26022e918cd27ce52bf545de4e9e8706c09ae79783950c0cd9240f48257a18b437/8b3ffb8797137873efcfd1d66b29906118bade8f6110f2d82300189784fcf5033c38ffa7c442f64ff5779dba33f5df31f625/2df1f603ce2f857d962c238a9f9de1e03d528a45280b658918c9a7236dcc885f8076ffecccf12a985af2662623f0523a8f348f00ba74a3b3e30ecdb77c4ff786243dea1228ce47d2641a68b44a48d9f2e875e1bb588812c797877d03/FFU1.pnghttp://ovidsp.tx.ovid.com/mms/434f4e1a73d37e8cabd934ac87c62ccfbb26022e918cd27ce52bf545de4e9e8706c09ae79783950c0cd9240f48257a18b437/8b3ffb8797137873efcfd1d66b29906118bade8f6110f2d82300189784fcf5033c38ffa7c442f64ff5779dba33f5df31f625/2df1f603ce2f857d962c238a9f9de1e03d528a45280b658918c9a7236dcc885f8076ffecccf12a985af2662623f0523a8f348f00ba74a3b3e30ecdb77c4ff786243dea1228ce47d2641a68b44a48d9f2e875e1bb588812c797877d03/FFU1.pnghttps://www.bcbsri.com/BCBSRIWeb/images/image_popup/skin_type.jpghttps://www.bcbsri.com/BCBSRIWeb/images/image_popup/skin_type.jpg -
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Largest organ in the body
Represents approximately 16% of total body weight
An adult has on an average about 18-20 square feet
(about 2 square meters) of skin
6 million cells
5,000 sense end organs
400 cm nerve fibers
200 pain sensors
100 cm blood vessels
100 sweat glands
15 sebum glands 12 cold receptors
5 hairs
2 heat receptors
Each Sq.cm of skin is said to have approximately
Skin : Human integument
Anatomy
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Finger and toe nails :
Hair and hair follicles
Teeth
Sebaceous gland, sweat glands,
apocrine and mammary glands
Skin : Human integument
Specialized structures formed by skin
formed by
epidermis
and dermis
formed by epidermis
Skin - Dynamic organ - undergoes continuous changes throughout life
Anatomy
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Protective barrier interfacing with hostile environment
- Protects from trauma, UV light, toxins and bacteria Maintains temperature : Thermoregulation
Gathers sensory information from environment
Metabolic function: protein & Vitamin D metabolism
Functions
Skin - average pH - 5.5 - Acidic
Acid mantle - amino, lactic & fatty acids in sweat, sebum & hormones
Acid mantle allows resident protective microflora (bacteria and yeasts)
& repels pathogenic micro-organisms and reduces body odour
Skin : Human integument
Anatomy
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Immunological surveillance
Helps restrict fluid loss & preventsexcessive water absorption
Despite numerous beneficial properties, skin is often abused and
under-appreciated until its compromise results in pain and loss of
resistance to infection
Benjamin C Wood, 2010
Functions
Skin : Human integument
Anatomy
Immunological surveillance
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Skin thickness varies - location, gender, age
Thinnest : eyelid, postauricular
Thickest : palms and feet
Male skin thicker than females
Thin in children starts thickening from 11 years age
& until 4th-5th decade starts thinning again
Location
Gender
Age
Benjamin C Wood, 2010
Skin : Human integument
Anatomy
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Epidermis
Dermis
Subcutaneous
Single cell layers of epidermis and dermis start proliferating in the 4th
week of embryological life
3 layers of skin
Anatomy
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Outer layer of skin : 5% of skin
Keratinocytes structural cells
Avascular - gets nutrients and disposes waste
products by diffusion from underlying dermis through
basement membrane which separates the 2 layers
Epidermis Derived from ectoderm
Anatomy
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Melanocyte
Cornified layer (St. Corneum)
Transitional layer (St. Licidum)
Granular layer (St. Granulosa)
Spinous layer
(St. Spinosa)
Basal layer
(St. Basale)
Malphigian layer
Basal Lamina
Melanosomes
Keratingranules
Keratin
Anatomy
Epidermis
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Epidermis
layers
Characteristics
Stratum Basale Undifferentiated columnar stem cells.
Constantly renews epidermal cells
Stratum Spinosum
(Malpighian layer)
Cells change from being columnar to
polygonal - cells start to synthesize keratin
Stratum
Granulosum
Cells have lost nuclei dark clumps of
cytoplasmic material -Keratin proteins &
water-proofing lipids - produced &
organizedStratum Licidum Only present in thick skin - reduces friction
& shear forces between str. corneum &
stratum granulosum
Stratum Corneum Cells flat - corneocytes. Cells fully mature -
keratinocytes with keratin protein first
Anatomy
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Anatomy
Melanocyte Langerhans' cell Merkel's cell
Special cell Function Origin Found in
Melanocyte Pigment - melanin Neural crest Basal layer, Hair follicles, Retina,Uveal tract & Leptomeninges
Langerhans Antigen processing Bone marrow Basal, Spinous & Granular layers
Merkel cell Sense light touch Neural crest Volar aspect of digits, Nail beds,Genitalia and Other areas of skin
Epidermis Specialized Epidermal Cells : 3 types
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Junction between epidermis &
dermis not straight - Finger like
upward and downward projection
of dermis and epidermis
Depth of these inter-digitations vary on the amount onshear force this part of the skin is subjected
Epidermal and Dermal papillae
Anatomy
Dermo - epidermis junction
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Lying on the surface of epidermis- there are elevations
& depressions - responsible for
formation of finger prints in an individual
Anatomy
Lamina
Lucida
Thinner
Lies directly beneath basal layer of
epidermal keratinocytes
Lamina
Densa
Thicker
In direct contact with underlying dermis
Dermo-epidermis junction
Epidermal ridges
Layers of Dermo-epidermis junction
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Epidermal appendages - Hair follicles, sebaceous glands, sweat glands,
apocrine glands - diverticula of epidermis into dermis
The primary function - sustain & support epidermis
Papillary layer Reticular layer
Upper, thinner layer Lower, thicker layer
Contains capillaries,
elastic and reticular
fibers & some
collagen
Has collagen, elastic fibers, larger
blood vessels, closely interlaced
elastic fibres, coarse collagen
parallel to surface, sensorystructures, fibroblasts &
epidermal appendages*
Anatomy
Dermis Corium Layer - Derived from mesoderm
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Found in the dermis it is formed by sebaceous; sweat;
apocrine and hair follicles
Important source of epithelial cells with potential for
division & differentiation
Re-epithelializes removed or destroyed epithelium :
eg: partial thickness burns, abrasions, SSG harvest
In the face, lies in subcutaneous fat - remarkable
ability of facial skin to repair deep cutaneous wounds
Collagen - 70% of weight of dermis. Type I (85%) & Type III (15%) of total collagen.
Elastic fibers constitute < 1% of weight of dermis - but plays enormous functionalrole by resisting deformational forces and returning the skin to its resting shape
Anatomy
Epithelial Appendages Intradermal epithelial structures
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Hair follicle & erector pili muscle
Sebaceous (oil) & apocrine (scent) glands
Eccrine (sweat) glands
Blood vessels & nerves
Specialized nerve cells
Meissner's & Vater - Pacini corpuscles
transmit sensations of touch & pressure
Anatomy
Dermis Specialised Dermal Cells
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Anatomy
Epidermis,Dermis & Subcutaneous layers of Skin
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Binds dermis to underlying organs
Layer of fat & connective tissue
with larger blood vessels & nerves
Has areolar & adipose tissue
Important in thermoregulation
Size varies throughout body &
from person to person
In females - 8% thicker than males
Subcutaneous layer also referred to as Panniculus Adiposus
Anatomy
Subcutaneous tissue : Hypodermis
Subcutaneous tissue
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Insulates the body
Provides protective padding
Serves as energy storage area
Houses drainage system of skin
Anatomy
Subcutaneous tissue : Hypodermis
Subcutaneous tissue
Over developed subcutaneous layer leads to obesity
Wasting causes skin wrinkling, sagging & premature aging
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Arise from underlying source vessels each supplies a
3-dimensional vascular territory from bone to skin -
Angiosome
Anatomy
Blood supply Cutaneous vessels
Directly from source artery
(septo/fasciocutaneous perforator)
From terminal branches of muscular vessel
(musculocutaneous perforator)
Emerges from deep fascia & travels toward skin
- forms extensive subdermal & dermal plexuses
Originates
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Dermis - horizontally arranged
superficial & deep plexuses -
interconnected by vessels oriented
perpendicular to skin surfaceCutaneous vessels anastomose with
other cutaneous vessels form
continuous vascular network in the
skin
Anatomy
Blood supply Cutaneous vessels
Convection from cutaneous vessels is a vital component of
thermoregulation
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From the subpapillary plexus of small
arterioles arise an arcade of capillaries
which loop upwards into each dermalpapilla
Anatomy
Blood supply
Cutaneous vessels
Venous drainage
Venous portions of capillary loops empty into postcapillary
venules of subpapillary plexus empty into larger venules
- eventually empty into small veins in S/C fat
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HAS IMPRESSIVE POWERS OF ADAPTATION
At rest (thermally neutral environment)
Skin receives 5- 10% of cardiac output
Can become 50-70% during severe heat stress Zero in a cold environment !
Vein Capacitance can increase volume by up to 1 liter
Specialized arteriovenous shunts - glomus bodies
exist - primarily concerned thermoregulation
Found most abundantly in dermis of the extremity
- Skin of hands, feet, nose & ears
Anatomy
Skin circulation
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Cutaneous blood flow : 10-20 times more thanrequired for essential O2 and metabolism
Large amounts of heat can be exchanged through
regulation of cutaneous blood flow Cutaneous vessels controlled by hypothalamus
and autoregulatory mechanisms (endothelium
& its sensory axon reflex) Controls vasoconstriction & vasodilatation
Anatomy
Skin circulation
Temperature regulation is maintained by having a high-flow arterial
system combined with a high-capacity, low-linear-velocity venous
system. This allows maximal heat exchange with the environment.
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The human adult wound healing process can
be divided into 3 distinct phases
Inflammatory phase
Proliferative phase
Remodeling phase
Physiology of wound healing
Stages of wound healing
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Within these is a complex and coordinated
series of events that includes
- Chemotaxis - Angiogenesis
- Phagocytosis - Epithelization- Neocollagenesis - New glycosiminoglycans
- Collagen degradation - Proteoglycans
- Collagen remodeling
Results in replacement of normal skin with scar
Physiology of wound healing
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Primary
Delayed primary
Secondary
Fourth category : In healing of partial skin
thickness wounds
Physiology of wound healing
Types of wound healing
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Occurs within hours of repairing a full-
thickness surgical incision The surgical insult results in the mortality of a
minimal number of cellular constituents
Wound heals with minimum scarring
Physiology of wound healing
Category 1 : Primary wound healing
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Wound edges are not reapproximated
Desired in contaminated wounds
By fourth day, phagocytosis of contaminated tissuestakes place and process of epithelization,
collagen deposition & maturation are occurring
Usually wound is closed surgically at this juncture If "cleansing" of wound is incomplete, chronic
inflammation ensues - results in prominent scarring
Physiology of wound healing
Category 2 : DelayedPrimary wound healing
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Full-thickness wound allowed to close & heal
More intense inflammatory response
Larger quantity of granulomatous tissue is
fabricated for wound closure
Pronounced contraction of wounds
Physiology of wound healing
Category 3 : Secondary wound healing
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Involving only epidermis & superficial dermis
Epithelialization - predominant method of
healing
Wound contracture not a common part of
this process
Physiology of wound healing
Category 4: In partial thickness skin wounds
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Initial phase Hemostasis
Following vasoconstriction platelets adhere to
damaged endothelium - discharge ADP, promoting
thrombocyte clumping - dams the wound
Alpha granules liberate platelet-derived growth factor
(PDGF), PF IV & TGF-b
Fibrinogen cleaved into fibrin - provides structural
support for cellular constituents of inflammation
Process starts immediately lasts few days
Physiology of wound healing
Events in wound healing
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Second phase - Inflammation
Begins in first 6-8 hours
Leukocytes (PMNs) engorge wound
TGF-b facilitates PMN migration from surrounding
blood vessels - "cleanse wound
Monocytes exude from vessels - called macrophages
- manufacture various growth factors help in
multiplication of endothelial cells, sprouting of new
blood vessels, duplication of smooth muscle cells
Physiology of wound healing
Events in wound healing
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Third phase - Granulation
This phase consists of different subphases.
Fibroplasia
Matrix deposition
Angiogenesis
Re-epithelialization
Fibroblasts lay new collagen of the subtypes I
and III
Physiology of wound healing
Events in wound healing
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Third phase Granulation
Wound suffused with GAGs and fibronectin
contribute to matrix deposition
Basic FGF & VEGF modulate angiogenesis
Re-epithelization occurs with the migration of cells
from the periphery of the wound
EGF key role in this aspect of wound healing
These subphases last up to 4 weeks
Physiology of wound healing
Events in wound healing
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Fourth phase - Remodeling
After 3rd wk wound undergoes constant
alterations - remodeling - last for years Collagen degraded and deposited in an
equilibrium-producing fashion
The collagen deposition in normal wound
healing reaches a peak by the third week
Physiology of wound healing
Events in wound healing
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Fourth phase Remodeling
Contraction of wound is an ongoing process from
proliferation of fibroblasts termed myofibroblasts,
which resemble contractile smooth muscle cells
Wound contraction - greater extent with secondary
healing than with primary healing
Maximal tensile strength - achieved by 12th week
Ultimate resultant scar has only 80% of tensile
strength of original skin that it has replaced
Physiology of wound healing
Events in wound healing
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The definition is often unclear
Broadest sense - anything that substitutes for
any of the skin functions eg: being impervious,
a polyethylene plastic wrap would minimizeevaporation from an open wound - could be
considered a skin substitute
A biologic skin substitute, to be more than adressing, should in some way be incorporated
into the healing wound
Biological Skin Substitutes
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The best skin substitute is the skin itself
Skin grafting is the best procedure has
limitations and hence the need for substitutes
Autografts : the patient is the donor
Allografts or homografts from one individual
to another within the same species Xenografts or heterografts from one species
to that of another different species
Biological Skin Substitutes
Skin grafts
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Nontoxic
Little or no antigenicity
Immunologically compatible
Does not transmit disease
Biologic or Artificial skin substitutes act as a model for the synthesis of
true dermis or epidermis, thereby reducing the amount of scar tissue
in the healing wound
Biological Skin Substitutes
Ideal Skin substitute
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Temporary cover - prevents dehydration
Keeps the wound bed moist (important for
wound healing) Some skin substitutes stimulate the host
to produce a variety of cytokines and growth
factors that promote wound healing
Biological Skin Substitutes
Role of Skin substitutes
More than 20 products commercially available today Auger FA, 2009
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Grafts of cultured epidermal cells no dermal
components : Epicel, Vivoderm, Myskin, Cellspray, Cryoskin
Dermal components alone: Dermagraft, Alloderm, Oasis
, Biobrane, Matriderm
Bi-layer substitutes containing both dermal &
epidermal elements : Integra, Apligraf, Orcel, Permaderm
Biological Skin Substitutes
Three categories
A tool to rapidly cover or even close soft tissue deficits (wounds and
burns) without the well-described liabilities of donor site morbidity
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Further categorised
Acellular
Cellular
cellular therapy, tissue engineered products
Dermal Substitutes
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Can be permanently incorporated into patients new
skin layers without being rejected
They are immediately available
Avoids risks of cellular allogeneic materials
Use of thinner STSG reduced donor site morbidity and
improved incorporation
Advantages
Alloderm, Strattice , SurgiMend ,GraftJacket, NeoForm &DermaMatrix - composed of cadaveric dermis - serves as
a scaffold for the in-growth of recipient tissue
Dermal Substitutes
Acellular Dermal allografts
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Composed of collagen or polymer based
scaffold that is seeded with fibroblasts from a
donor cadaver
Used to cover partial & full thickness wounds
Must be removed or excised prior to grafting
full-thickness wounds
Eg: ICX-SKN, Dermagraft, TransCyte
Dermal Substitutes
Cellular Dermal allografts
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Bilayer products : Eg: Apligraf , Orcel
Dermal - bovine collagen & neonatal fibroblasts
Epidermal layer - neonatal keratinocytes
Allogeneic : cannot be used as permanent skin
substitutes rejected
Used in Tx of chronic wounds & donor sites
Used as overlay dressing on STSG to improve
function and cosmosis
Dermal Substitutes
Composite Dermal allografts
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Wound closure
Requires a material to restore the epidermal barrier
function and become incorporated into the healing
wound
Eg: Bilaminate membrane, Transcyte (Dermagraft-TC),
Cultured allogenic keratinocytes, Apligraf (human skin
equivalent), Dermograft
Wound coverage
Rely on ingrowth of granulation tissue for adhesion
Eg: Alloderm, Integra, Cultures autologous keratinocytes
Biological Skin Substitutes
In chronic wounds : two groups
l b i
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Current research in molecular biology, wound
healing and immunology - likely to yield
better skin substitutes
Possible for a synthetic bilayered membrane
of equal quality to that of skin to be available
off the shelf for application that is no moredifficult than a change of dressing
Maurice M Khosh,2008
Molecular Biology
Dermal Substitutes
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THANK YOU FOR YOUR
KIND ATTENTION