The body has a remarkable ability to heal itself.

Superficial wounds heal through simple proliferation of epithelial cells. This process is termed regeneration.

On the other hand, deep wounds trigger fibroblasts and chronic inflammatory cells to form a repair tissue rich in adhesive proteins. This extracellular matrix serves as a scaffold for the differentiation and morphogenesis of new parenchymal cells.

Repair tissue in a deep wound is also called granulation tissue, because it is rich in capillaries. The process of new capillary growth in healing wounds is termed angiogenesis.

Adequate arterial blood supply is a critical determinant of the outcome of wound healing. Lack of adequate perfusion leads to a failure of wounds to heal, with the development of chronic ulcers.

Here are the Key Points:

1. Simple abrasions heal by epithelial cell regeneration.

2. Deep wounds undergo repair by formation of granulation tissue.

3. Granulation tissue is rich in capillary endothelial cells and fibroblasts.

The following images illustrate Key Morphological Concepts:

1. This is an example of a HEALED MYOCARDIAL INFARCT. Note the triangular region of scar tissue in the left ventricle, the site of a previous transmural infarct.

2. This is an example of a SCAR TISSUE in a healed myocardial infarct. The blue-stained material in this microscopic image is a collagen-rich extracellular matrix, which fills a space previously occupied by cardiac myocytes. Healthy cardiac myocytes (red cells) are seen around the periphery.

3. This is an example of a CHRONIC ULCER on the foot of a patient with poor peripheral circulation. The red flesh in the center of this ulcer is granulation tissue that has failed to undergo re-epithelialization and differentiation of skin.

4. This is an example of a HYPERTROPHIC SCAR. These scars are also referred to as keloids. They are thought to arise due to a defect in the maturation of extracellular matrix in granulation tissue. Hypertrophic scars are more commonly seen in blacks than in whites.