The pathological processes involved in healing are of fundamental importance to all clinical practitioners. They are of particular significance for surgeons because tissue injury is an inevitable consequence of any operative procedure and surgeons are concerned not only with the functional results, but also the cosmetic consequences of their operat...

A fundamental aspect of how a tissue responds to injury is whether the cells are capable of replication to replace those that are lost. This capability depends on the presence of stem cells that can be stimulated to multiply appropriately. Classically, tissues have been described as being of three types in this regard: labile, stable and permanent (Table 1).

Table 1. Characteristics of labile, stable and permanent cell types

Much of our knowledge of healing comes from studies in the skin, and the healing of skin wounds is a useful exemplar for wound healing in general.1,3,5 There are two basic patterns:

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Healing by primary intention or primary union, in which there is minimal granulation tissue and scarring.

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Healing by secondary intention or secondary union, in which large amounts of granulation tissue form with significant resultant scarring.

These processes are compared and contrasted in Table 2. Other models of healing in the skin also exist, for example delayed primary union, in which a contaminated wound is left open for a few days to allow drainage and then closed. Skin healing follows the typical pattern of haemostasis, inflammation, proliferation and remodelling.