Final answer:
Granulation tissue fills the wound during the proliferative phase of deep wound healing, largely due to collagen deposition by fibroblasts and the formation of new blood vessels through angiogenesis.
Step-by-step explanation:
Granulation tissue fills the wound during the proliferative phase of deep wound healing. This process occurs after the initial hemostasis and inflammatory phases. During the proliferative phase, fibroblasts from the surrounding connective tissues proliferate and begin to lay down a new extracellular matrix, depositing collagen to restore the structural integrity of the tissue. Concurrently, angiogenesis takes place, leading to the formation of new blood vessels, which is a hallmark of granulation tissue formation. As this new tissue fills the wound, it appears granular and reddish due to the presence of capillaries, hence the name granulation tissue. Eventually, the wound contracts as the clot dissolves, and the granulation tissue is replaced by scar tissue in a process known as remodeling or maturation.