SKIN an Integument

7/31/2019 SKIN an Integument

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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


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


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


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


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



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Primary

Delayed primary

Secondary

Fourth category : In healing of partial skin

thickness wounds


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


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


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


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


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


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




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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




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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




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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




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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




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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


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


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


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


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


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

SKIN an Integument

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