Scar

A scar is a mark from an injury.

Your body uses a special protein to fix the spot. This protein is called collagen.

In normal skin, the fibers are like a messy basketweave. In a scar, the fibers line up in one direction. This makes the skin feel stiff.

Some scars are raised lumps. Other scars look like sunken pits. Scars do not have hair or sweat glands.

Stretch marks are also a type of scar. They happen when skin stretches fast.

Even your belly button is a scar. It heals after the cord is cut. Scars show how your body heals.

A scar is a mark left by an injury. It is a natural part of how your body heals.

When you get hurt, your body works to fix the damage. It uses a protein called collagen. In normal skin, collagen fibers look like a messy basketweave. In a scar, the fibers line up in one direction. This makes the scar tissue stiff and less stretchy. Scars also do not have hair or sweat glands.

There are different kinds of scars. Hypertrophic scars are red, raised lumps. Keloid scars are a more serious type. They can grow larger than the original wound. Atrophic scars are sunken pits in the skin.

Some scars happen when skin stretches very fast. These are called stretch marks. Even your belly button is a scar. It forms after the umbilical cord is cut at birth. Most scars stay for a long time. Some may even take years to settle.

A scar is a patch of fibrous tissue. It replaces normal skin after an injury occurs. This is a natural part of how the body repairs itself. Most wounds from accidents, diseases, or surgeries result in some scarring.

Some animals can regrow tissue perfectly without any scars at all. However, most humans and other mammals heal by making scar tissue. This tissue is different from the skin we are born with. It helps close a wound, but it works differently than healthy skin.

To understand how it works, we look at a protein called collagen. In normal skin, collagen fibers look like a messy basketweave. When a wound heals, the body uses cells called fibroblasts to patch the damage. These cells create a dense collagen matrix to fill the gap. In a scar, these fibers line up in a single direction.

This alignment makes the tissue stiff and less stretchy. Because of this, scars do not have hair follicles or sweat glands.

Scientists and doctors have studied these different types of healing for a long time. For example, we know that wounds smaller than 2mm usually heal without a scar. We also know that mechanical stress can make scarring worse. In 2011, researchers found that stress on a wound stimulates more scarring. By 2021, scientists found that using chemicals to stop cells from sensing stress helped wounds heal without scars.

These discoveries help us understand how to treat injuries better.

There are several specific types of scars you might see. Hypertrophic scars are raised, red lumps that stay within the original wound area. Keloid scars are more serious because they can grow much larger than the injury. They are most common in people with dark skin and often appear on the chest or shoulders.

Atrophic scars are sunken or pitted in the skin. These often happen when underlying fat or muscle is lost. Stretch marks, or striae, are also a form of scarring caused by rapid stretching.

Scars connect to many parts of our lives and bodies. Even your belly button is a scar from when your umbilical cord was cut. Some people use medical treatments to help with scars. For instance, chemical peels can help with superficial acne scars. Doctors can also use filler injections to raise sunken atrophic scars.

While scars can sometimes be itchy or painful, they are a sign that your body is working hard to keep you safe.

A scar is an area of fibrous tissue that replaces normal skin after an injury. This process is a natural part of wound repair in the skin and other organs. While some animals can undergo complete regeneration to regrow tissue perfectly, most mammals heal through scarring.

Except for very minor lesions, almost every wound from an accident, disease, or surgery results in some scarring. This happens when the body prioritizes closing a gap over perfectly recreating the original structure.

To understand how a scar forms, we must look at the biological mechanism of repair. When an injury occurs, the body first creates a clot to patch the damage. This clot acts as a provisional matrix, which is a temporary structure for healing. Following this, cells called fibroblasts begin a process known as fibroblast proliferation. These cells migrate to the site to lay down collagen, a structural protein.

In normal tissue, collagen fibers form a random basketweave pattern. However, during fibrosis, these fibers cross-link and align in a single direction. This dense, aligned collagen creates an inelastic, whitish scar wall that blocks cell communication.

A specialized type of cell called a myofibroblast plays a critical role in this process. Myofibroblasts are contractile fibroblasts that express a protein called alpha-smooth muscle actin (alpha-SMA). They are responsible for wound contraction, which helps pull the edges of a wound together. In some animal models, such as rats, myofibroblasts can make up as much as 70% of the proliferating fibroblasts. While these cells usually disappear within 30 days, they can remain in pathological cases. This presence can lead to excessive tissue growth and stiffness.

Scars vary significantly in their physical appearance and behavior. Hypertrophic scars are raised, red lumps caused by the overproduction of collagen. They typically appear within four to eight weeks after a wound closes under tension. Keloid scars are a more serious form of excessive scarring. Unlike hypertrophic scars, keloids can grow indefinitely into large, benign neoplasms, or non-cancerous growths.

Keloids are most common in people with dark skin and often appear on the chest or shoulders.

Another distinct type is atrophic scarring, which creates a sunken or pitted appearance in the skin. This occurs when the underlying structures, such as fat or muscle, are lost during the healing process. Atrophic scars are often associated with acne, chickenpox, or certain infections like Staphylococcus.

Some people also develop striae, commonly known as stretch marks. These are a form of scarring caused by skin stretching rapidly during growth spurts or pregnancy. Even the umbilical scar, or belly button, is a result of the healing process after the umbilical cord is cut.

The quality of scar tissue is often inferior to the original tissue. Because the collagen is so densely packed and aligned, scars lack elasticity. They also do not contain sweat glands or hair follicles. This means scar tissue cannot regulate body temperature as effectively as normal skin. Furthermore, scars are less resistant to ultraviolet radiation. In internal organs, scarring can be even more significant. For example, a myocardial infarction, or heart attack, causes scar formation in the heart muscle. This can lead to a loss of muscular power and potentially heart failure.

Research has revealed how external factors influence the healing process. In 2011, scientists discovered that mechanical stress can stimulate the formation of scars. Conversely, "stress shielding" can help reduce scarring. By 2021, researchers found that using chemicals to prevent fibroblasts from sensing mechanical stress allowed for scar-free healing. Understanding these mechanisms helps in developing treatments. For instance, chemical peels can exfoliate superficial acne scars. Doctors may also use filler injections of collagen to raise atrophic scars to the level of the surrounding skin.