[Biology Class Notes] on Scar Pdf for Exam [2024]

After an injury, a scar is an area of fibrous tissue that replaces normal skin. Scars form as a result of the body’s organic wound-healing process, which occurs in the skin as well as other organs and tissues. A scar is created when the deeper layer of the skin, the dermis, is damaged. Damage to the epidermis, the skin’s most superficial layer, may not always result in a scar. Scars cause a structural change in the skin’s deeper layers, which is seen as a modification in the architecture of the usual surface characteristics. It is more than just a change in skin tone. Fetal and mucosal tissues are capable of healing without leaving a scar.

Pathophysiology of Scar Formation

Scar tissue is made up of the same protein (collagen) as the tissue it replaces, but the fibre composition of the protein is different instead of the random basketweave formation of collagen fibres found in normal tissue, collagen cross-links and forms a pronounced alignment in one direction in fibrosis. The functional quality of this collagen scar tissue alignment is usually lower than that of the regular collagen randomly alignment.

After tissue injury, the body’s repair system produces a scar. If a wound heals within two weeks with new skin creation, just a small amount of collagen is deposited, and no scar is formed.
Tissue scars when the extracellular matrix detects increased mechanical stress loading and scarring can be reduced by stress shielding wounds.
Small full-thickness wounds less than 2mm regrow epithelial tissue quickly and heal without scarring.
Scarring and hair loss are common side effects of deep second-degree burns.
Scar tissue lacks sweat glands, making it difficult to regulate body temperature. Elastic fibres are rarely found in scar tissue that is less than three months old.
The endometrium, or inner lining of the uterus, is the only adult tissue that undergoes rapid cyclic shedding and regeneration without scarring on a monthly basis it sheds and regenerates within a 7-day window. All other adult tissues can scar if they are shed quickly or if they are injured.
Prolonged inflammation and fibroblast proliferation are possible side effects. Redness that occurs after a skin injury is not a scar and is usually not permanent. The time it takes for this redness to fade can vary from a few days to a few years in certain extreme and unusual cases.
Scars development vary depending on the location of the damage on the body and the age of the injured person.
The scar will usually be worse if the initial harm is severe. When the dermis, the deep, thick layer of skin, is injured, skin scars form. The majority of skin scars are flat and leave no evidence of the initial incident.
Wounds that are allowed to heal secondary scar more than wounds that are closed completely.
Any wound does not become a scar until it has healed entirely, which can take months or even years in the most severe pathological cases, such as keloids.
A clot is formed to begin the process of repairing the damage. This clot is the first step in the process of creating a provisional matrix.
The first layer of the procedure is a temporary matrix that does not scar. Over time, the injured bodily tissue overexpresses collagen inside the provisional matrix, resulting in the formation of a collagen matrix.
This collagen overexpression continues, crosslinking the collagen matrix’s fibre arrangement and making the collagen thick.
This densely packed collagen blocks cell communication and regeneration, morphing into an inelastic whitish collagen scar wall; as a result, the new tissue generated will have a different texture and quality than the surrounding unwounded tissue. A Fortuna scar is the result of a prolonged collagen-producing process.
Fibroblast growth which begins with a reaction to the clot causes scarring. Fibroblasts slowly produce the collagen scar to repair the injury.
The fibroblast growth is circular and cyclic, resting thick, whitish collagen inside the provisional and collagen matrix, resulting in an abundance of packed collagen on the fibres, which gives scars their uneven texture.
The fibroblasts continue to crawl throughout the matrix, modifying additional fibres, and the scarring settles and stiffens as a result.
The tissue compresses as a result of fibroblast growth. These fibres are not overexpressed with thick collagen in unwounded tissue and do not contract.
Mammalian wounds that involve the skin’s dermis heal through repair rather than regeneration.
Full-thickness wounds heal through a combination of wound contracture and epithelial tissue regeneration at the margin.
Partial-thickness wounds heal through epidermal migration from adnexal structures including hair follicles, sweat glands, and sebaceous glands, resulting in the regeneration of epithelial tissue and epidermal migration.
The exact location of keratinocyte stem cells is uncertain, however, they are most likely to be found in the epidermis’ basal layer and under the bulge area of hair follicles.
The myofibroblast, a specialised contractile fibroblast, is the fibroblast involved in scarring and contraction. 𝜶- smooth muscle actin (𝜶- SMA) is expressed in these cells.
The myofibroblasts are absent in the first trimester o
f the embryonic stage, where damage heals scar-free in small incisional or excision wounds less than 2 mm, which also heal without scarring, and in adult unwounded tissues, where the fibroblast is arrested, but the myofibroblast is found in massive numbers in adult wound healing, which heals with a scar.
At the start of healing, myofibroblasts make up a large fraction of the fibroblasts multiplying in the postembryonic lesion. Myofibroblasts usually leave the site after 30 days, but they might linger in pathological situations of hypertrophy, such as keloids.

Types of Scar

1. Hypertrophic Scars

When the body overproduces collagen, the scar rises above the surrounding skin, resulting in hypertrophic scars.
For lighter coloured skin, hypertrophic scars appear as a red elevated lump on the skin, whereas darker pigmented skin appears as a dark brown.
They commonly appear 4 to 8 weeks after a wound infection or wound closure involving excessive tension or other severe skin damage.

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2. Keloid Scars

Keloid scars can grow endlessly into big, tumorous neoplasms, they are a more dangerous kind of excessive scarring.
The lack of growth outside the initial wound region distinguishes hypertrophic scars from keloid scars, yet this often taught distinction can cause confusion.
Keloid scars can affect anyone, however, they are more common in persons with dark skin. Surgery, an accident, acne, and, in some cases, body piercings can all cause them. Keloid scars develop spontaneously in certain people.
Keloid scars are inert masses of collagen that are absolutely innocuous and non-cancerous, despite the fact that they can be a cosmetic issue. They can, however, be irritating or uncomfortable in some people.
They are most commonly found on the shoulders and chest. In wounds closed by secondary intention, hypertrophic scars and keloids are more common.
Surgical excision of a keloid is dangerous, as it may aggravate the condition and cause the keloid to worsen.

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3. Atrophic Scars

Atrophic scars appear as a deep hole in the skin that is pitted in appearance.
These are caused by the loss of underlying components that support the skin, such as fat or muscle.
Acne, chickenpox, other infections, including Staphylococcus infection, surgery, certain insect and spider bites, or accidents are all common causes of this form of scarring.
A genetic connective tissue disorder, such as Ehlers–Danlos syndrome, can also cause it.

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4. Stretch Marks

Stretch marks, commonly known as striae, are a type of scarring.
When the skin is stretched rapidly, such as during pregnancy, major weight gain, or teenage growth spurts, or when the skin is put under tension during the healing process, commonly near joints, they occur. After a few years, this type of scar normally improves in appearance.
The development of striae has been linked to elevated corticosteroid levels.

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5. Umbilical Scars

When the umbilical cord is cut after delivery, humans and other placental mammals have an umbilical scar that is generally referred to as a navel.
Egg-laying mammals have an umbilical scar that might last a lifetime or go away within a few days after delivery, depending on the species.

Acne Scars

Inflamed blemishes created by skin pores clogged with excess oil, dead skin cells, and bacteria are the most common cause of acne scars. The pore swells create a follicular wall breach. The majority of shallow lesions are small and heal fast sometimes form scars face. By generating new collagen fibres, the skin strives to mend these lesions.

Types of Acne Scars

Ice-pick scars: These are scars that are deep, thin, and pitted.
Rolling scars: These are large depressions with a slanted edge.
Boxcar scars: These are deep depressions with well-defined edges.
Atrophic scars: These are scars that are flat, thin, or depressed (anetoderma)
Hypertrophic or Keloid scars: These scars are thick and lumpy.

Acne Scar Treatment

There are various scar treatment and remedies to control and prevent acne scars face. A few of the best scar removal methods are listed below:

1. Home skincare

2. Soft tissue fillers

Collagen filler injections can be utilised to bring atrophic scars up to the level of the surrounding skin. The risk of additional deformity and adverse reaction varies depending on the filler used.

3. Steroid injection

Corticosteroid injections into the scar for a long period of time may help flatten and soften the appearance of keloid or hypertrophic scars.

4. Laser resurfacing

For hypertrophic scars and keloids, nonablative lasers such as the 585 nm pulsed dye laser, 1064 nm and 1320 nm Nd: YAG, or 1540 nm Er: Glass are employed. Burn
scars appear to improve the appearance, according to preliminary studies. Atrophic and acne scars respond well to ablative lasers like the carbon dioxide laser or Er: YAG.

5. Dermabrasion

Dermabrasion is an exfoliating method that removes the outer layers of skin from the face using a spinning device. This therapy is popular among people who want to improve their skin’s appearance. Fine wrinkles, sun damage, acne scars, and uneven texture are just a few of the ailments it can help with.

6. Chemical peel

Chemical peels are chemicals that degrade the epidermis in a regulated manner, resulting in exfoliation and the relief of specific skin disorders, such as acne scars.

7. Skin needling

Microneedling is a dermaroller process that pricks the skin with minuscule needles. The goal of the therapy is to stimulate the production of new collagen and skin tissue, resulting in skin that is smoother, firmer, and more toned. Microneedling is most commonly used on the face to treat scars, wrinkles, and enlarged pores.

8. Surgery

Other techniques, such as pressotherapy or silicone gel sheeting, are frequently used in conjunction with surgical removal of hypertrophic or keloid scars. Scar revision is a procedure that involves removing scar tissue. The new wound is frequently closed up to heal by primary intention, rather than secondary intention, after the excision. Subcision is a procedure for removing deep rolling scars caused by acne or other skin conditions.

Conclusion

Scarring is an unavoidable consequence of the healing process. Every wound following an accident, disease, or surgery, with the exception of very tiny lesions, results in some degree of scarring. Scars look as firm red to the purple fibrous tissue that becomes flatter and lighter in colour over time at the location of tissue damage. Visual examination is almost often used to diagnose scars. In a few rare circumstances, it may be required to study scar tissue under a microscope to determine its true nature. This would necessitate a skin biopsy and possibly the injection of a topical anaesthetic.