When a tendon heals naturally, what type of collagen fiber is the first to be deposited?

During the natural healing process of a tendon, the first type of collagen that is typically deposited is Type III collagen. This initial phase of healing is characterized by the formation of granulation tissue, which is rich in Type III collagen due to its ability to provide structural support and facilitate the cellular processes involved in the healing response. Type III collagen is produced by fibroblasts during early stages, providing a temporary scaffold that is later remodeled into stronger Type I collagen as healing progresses.

In contrast, Type I collagen is the primary structural component of mature tendon tissue and is more commonly associated with the later stages of healing and tissue remodeling. Type II collagen is primarily found in cartilage and is not predominant in tendons. Type VII collagen is involved in anchoring structures in skin and is not relevant to tendon healing. Therefore, the correct recognition of Type III collagen as the first to be deposited highlights its crucial role in initiating the repair mechanisms of tendon tissue.