Tattoo Ink - Where Does It All Go (2024)

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Tattoo Ink - WhereDoes It All Go?

Disclaimer:Allimages here are rough representations. Please read the text, not just thecaption, for a full explanation. Also, the information presented here isin no way guaranteed to be complete, however I have tried to piece togetheras much of the puzzle as possible. Feel free to contact me if errors oromissions are found.

Contents:

Introduction
Jargon - feel free to skip this section, but it may be usefulto refer to while reading the text
The Skin
- Epidermis
- Dermis
Tattoo Ink Placement
Stages of Ink Dispersal
- Then why does the tattoo fade over time?
- What about the sun?

Introduction:

Tattooink dispersal in the skin has not been thoroughly studied despite the longhistory of tattooing. The following is whatever I have managed to piecetogether from journal articles and textbooks. For those of you who wouldlike to read the original science jargon, or to read about different inkparticle sizes (depends on the colour) check out these links:

TattooInk Removal - Covers the Location of Tattoo Ink and Ink Particle Sizes
ALecture About Skin - Covers Cellular Detail

Jargon:

Theseare some definitions that may be useful.

Extracellular- outside of the cell
Intracellular - inside the cell
Phagocytosis - think of it as the cell swallowing anitem e.g. a particle of tattoo ink
Phagocytic - cells that are capable of phagocytosis;some cells can become phagocytic during an inflammatory response (e.g.keratinocytes), whereas others are phagocytic all the time (e.g. many immunecells).
Dendritic Cell - an immune cell type that continuallysamples its environment for changes, and will migrate to lymph nodes totrigger an immune response if necessary.
Mast Cell - an immune cell that plays a crucial rolein allergic reactions and is present in connective tissue.
Extracellular matrix - a generic name for the scaffoldof proteins (both structural and "glue" types) that cells attach to andare supported by. Major components include basem*nt membrane (one typeof collagen network), elastic fibers, structural glycoproteins (e.g. fibronectin),proteoglycans("glue") and collagen.
Fibrocyte - a cell type that makes up most of the cellsin connective tissue. They secrete collagen as well as other proteins thatmake up the extracellular matrix when activated. They are not normallyphagocytic, but become so when inflammation occurs.
Fibroblast - a fibrocyte that is actively secreting proteins(an active fibrocyte).
Granulation tissue - tissue that fills in gaps formedfrom debris or necrotic tissue removal. It consists of newly formed smallblood vessels embedded in a loose structure of fibroblasts and immune cells.As the tissue matures, immune cells decrease in number, fibroblasts formcollagen networks and blood flow resumes to the area.

The Skin

Theskin is made up an outermost layer named the epidermis, followed by thedermis and the hypodermis.

<![if !supportLists]>·<![endif]>Epidermis:composed mostly of keratinocytes, cells that contain keratin, the proteinthat gives skin its toughness (not to be confused with collagen which givesskin its resiliency).

<![if !supportLists]>·<![endif]>Dermis:a network of elastic dense connective tissue containing collagen as wellas sweat glands, hair follicles, sebaceous ("oil") glands, nerve endingsand blood vessels.

<![if !supportLists]>·<![endif]>Hypodermis:loose connective tissue containing mostly adipose (fat) tissue.

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Fig.1 The Three Layers of the Skin

Epidermis

Theepidermis is separated from the dermis by a basem*nt membrane (an extracellularnetwork of collagen fibers that serves as a support framework for cells)that strengthens the interface between the epidermis and dermis to preventtearing from excessive stretching.

Thereare five layers of the epidermis, where the surface layers are regeneratedfrom stem cells in the deepest layer that differentiate as they move outwards:

<![if !supportLists]>·<![endif]>Stratumbasale (deepest)

<![if !supportLists]>·<![endif]>Stratumspinosum

<![if !supportLists]>·<![endif]>Stratumgranulosum

<![if !supportLists]>·<![endif]>Stratumlucidum

<![if !supportLists]>·<![endif]>Stratumcorneum (surface)

Briefly,the stratum basale contains keratinocyte stem cells ("basal cells") thatare continually dividing to create new cells. These cells differentiate,or in other words change, as they migrate through the layers to the surface.The stratum granulosum is the "waterproofing" layer of cells, and cellsno longer divide at this level. The outermost surface layer is composedof dead keratinocytes which are essentially cells filled with keratin.

Dermis

Thedermis, a connective tissue made up of collagen and networks of elasticfibers which give skin its resiliency, is the layer in which tattoo inkis deposited. The dermis (papillary layer) immediately below the epidermisis made of loose connective tissue and contains small blood vessels andnerve endings. The rest of the dermis (reticular layer) is made of denseconnective tissue and contains blood vessels, hair follicles, sweat glands,lymphatics, nerves, and sebaceous glands.

Themajority cell type in the dermis is fibrocyte (or fibroblast). These cellssecrete the proteins that make up the connective tissue network. Othercells that are important in relation to tattoo ink are resident immunecells. These include dendritic cells, macrophages, and mast cells.

TattooInk Placement

Thetattooing process causes damage to the epidermis, epidermal-dermal junction,and the papillary layer (topmost layer) of the dermis. These layers appearhom*ogenized (or in other words, like mush) right after the tattooing process.The ink itself is initially dispersed as fine granules in the upper dermis,but aggregate into more concentrated areas at 7-13 days.

Likeany injury, the initial response is to stop bleeding, followed by tissueswelling, and the migration of non-resident immune cells into the area.The "automatic response" immune cells are mostly neutrophils, and macrophageslater on. They are phagocytic cells that "swallow" debris to clean up thearea and then leave via the lymphatics. This is the extent of an immuneresponse unless an allergic reaction occurs or an infection sets in. Thetissue is then repaired and/or regenerated by fibroblasts. Initially thetissue formed is known as granulation tissue (think fresh scar, pinkishand soft), which later matures into fibrous tissue (think old scar).

Stagesof Ink Dispersal

Initiallyink is taken up by keratinocytes, and phagocytic cells (including fibroblasts,macrophages and mast cells).

Atone month the basem*nt membrane of the epidermis (epidermal-dermaljunction) is reforming and the basal cells contain ink. In the dermis,ink containing phagocytic cells are concentrated along the epidermal-dermaljunction below a layer of granulation tissue that is surrounded by collagen.Ink is still being eliminated through the epidermis with ink present inkeratinocytes, macrophages and fibroblasts.

Attwo to three months the basem*nt membrane of the epidermis is fullyreformed, preventing any further loss of ink through the epidermis. Inkis now present in dermal fibroblasts. Most of these ink containing fibroblastsare located beneath a layer of fibrous tissue which has replaced the granulationtissue. A network of connective tissue surrounds and effectively trapsthese fibroblasts. It is assumed that these fibroblasts are the cellsthat give tattoos their lifespan.

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Fig.2 Injured Tissue: Ink is deposited into the upper surface of thedermis upon needle entry.

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Fig.3 Ink Location: soon after the tattoo is received, one month after,and two to three months after. Note the reformation of the epithelial-dermaljunction over time and the concentration of ink just underneath it.

Then why does the tattoofade over time?

Itis debated whether all the ink particles are in fibroblasts, or if someremain as extracellular aggregations of ink. Also, the lifespan of theink containing fibroblasts is not known. Presumably, ink particles aremoved into the deeper dermis over time due to the action of mobile phagocyticcells (think immune cells), causing the tattoo to look bluish, faded andblurry. Examination of older tattoos (e.g. 40 years) show that the inkis in the deep dermis, and also found in local lymph nodes. Since sometypes of phagocytic immune cells migrate to lymph nodes to "present theirgoods", the discovery of ink in lymph nodes is consistent with the theoryof phagocytic cells being the cause of ink movement.

Whatabout the sun?

Sunexposure equals sun damage, whether you realize it or not. Langerhans cells,a type of dendritic cell, are present throughout the epidermis, but mostlylocated in the stratum spinosum. During sun exposure, many Langerhans cellswill undergo apoptosis (a type of cell death where the cell breaks apartinto many small fragments) while others migrate into the dermis and a minorinflammatory reaction occurs. The inflammatory reaction is not restrictedto the epidermis, but also involves the dermis. Such a reaction causesthe recruitment of more phagocytic immune cells to the area.

Withthe presence of larger than normal amounts of migrating phagocytic cells,the chances of ink movement increases, thus accelerating the fading ofthe tattoo.

Compiled:January 13 2003

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