What is the Difference Between Scar Tissue and Normal Skin Tissue?

Scar tissue and normal skin tissue have several differences in their structure, biomechanical properties, and function. Some of the key differences include:

1. Orientation of collagen fibers: In normal skin tissue, collagen fibers are oriented randomly, while in scar tissue, they are aligned parallel to each other and the plane of the skin.
2. Biomechanical properties: Scar tissue exhibits similar high-load stiffness as uninjured skin, but it has a greatly reduced resistance to failure, reduced low-load compliance, and altered material directionality. Scar tissue is also stiffer than healthy skin, muscle, and fat, and is less pliable, making it less able to withstand being stretched or deformed without being damaged.
3. Low-load behavior and viscoelasticity: Scar tissue has a greater viscous content, relaxing faster than uninjured skin. It also shows no directional differences in failure properties, low-load behavior, or relaxation rate.
4. Structure and composition: Normal skin tissue has layers with hair follicles and sweat glands, while scar tissue lacks these layers and dermal appendages. Scar tissue is also composed of parallelly oriented collagen fibers, unlike the randomly oriented collagen fibers in normal skin tissue.
5. Vulnerability to external factors: Scar tissue is more vulnerable to factors such as poor nutrition, moisture, heat, smoking, and unrelieved pressure, which can threaten its integrity and lead to further damage.
6. Appearance: Scar tissue often has a different texture and quality than the surrounding tissue, and it may have a flat, pale, raised, or pitted appearance depending on the type of scar and the individual's skin.

Comparative Table: Scar Tissue vs Normal Skin Tissue

Scar tissue and normal skin tissue have distinct differences in their structure, composition, and function. Here is a table comparing the two:

Scar tissue is formed as a result of the wound healing process in normal skin, and it is composed of parallelly oriented collagen fibers. Scar tissue lacks hair follicles and does not have the same pigmentation as normal skin due to the absence of melanin, melanoid, and carotene. Scar tissue is also less resistant to UV rays and more vulnerable to environmental factors like poor nutrition, moisture, heat, and smoking.

Normal skin tissue, on the other hand, is composed of randomly oriented collagen fibers and includes hair follicles, sweat glands, and other dermal appendages. The outermost layer of normal skin is the epidermis, which acts as a waterproof barrier, and the layer below the epidermis is the dermis, composed of connective tissue that protects from strain and stress. The hypodermis, located below the dermis, attaches the skin to the underlying tissue and serves various functions like heat regulation, absorption, and excretion.