I have a quick clarification question for you about the difference between granuloma and granulation tissue. I have in my notes that “a granuloma is a type of chronic inflammation where you have macrophages that surround something indigestible like a splinter.”
How, then, would you define granulation tissue that is present in the 3-5 days following injury? Is the difference simply that granulation tissue is not necessarily something that surrounds an indigestible particle, but rather a tissue that characterized by the presence of macrophages, collagen/fibroblasts, and blood vessels?
A. Yes! You’re on the right track. I think it might be helpful to think about the differences between granulation tissue and granulomas in two categories: function and composition.
The function of granulation tissue is to provide the building blocks necessary for the healing of the injured tissue. The function of a granuloma, on the other hand, is to surround and (hopefully) digest foreign substances (splinters, difficult-to-kill bugs like mycobacterium tuberculosis).
There really isn’t any crossover, either – you don’t see granulation tissue at the site of a foreign body, and you don’t see granulomas forming in wound healing. So the functions of granulation tissue and granulomas are quite different.
Their composition is different too. Granulation tissue is composed of blood vessels, fibroblasts, and loose extracellular matrix. Granulomas are composed of macrophages and (often) a collar of surrounding lymphocytes. Macrophages do participate in wound healing, but they’re not part of granulation tissue. So the composition of granulation tissue and granulomas are very different too.