the healing stage Flashcards
what happens in the bleeding stage
The process of the wound being closed by clotting.
> Happens very quickly. (average 4/6 hrs)
Starts when blood leaks out of the body, then blood vessels constrict to restrict the blood flow.
The platelets aggregate and adhere to the sub-endothelium surface within seconds of the rupture of a blood vessel’s epithelial wall.
After that, the first fibrin strands begin to adhere in about sixty seconds.
As the fibrin mesh begins, the blood is transformed from liquid to gel through pro-coagulants and the release of prothrombin.
The formation of a thrombus or clot keeps the platelets and blood cells trapped in the wound area.
what happens in the inflammation stage
> Begins right after the injury when the injured blood vessels leak transudate (made of water, salt, and protein) causing localised swelling.
Inflammation both controls bleeding and prevents infection.
The fluid engorgement allows healing and repair cells to move to the site of the wound.
During the inflammatory phase, damaged cells, pathogens, and bacteria are removed from the wound area.
The white blood cells, growth factors, nutrients and enzymes create the swelling, heat, pain and redness commonly seen during this stage of wound healing.
Inflammation is a natural part of the wound healing process and is only problematic if prolonged or excessive.
what happens in the proliferation stage
When the wound is rebuilt with new tissue made up of collagen and extracellular matrix
> The wound contracts as new tissues are built.
A new network of blood vessels must be constructed so that the granulation tissue can be healthy and receive sufficient oxygen and nutrients.
Myofibroblasts cause the wound to contract by gripping the wound edges and pulling them together using a mechanism similar to that of smooth muscle cells.
In healthy stages of wound healing, granulation tissue is pink or red and uneven in texture. Healthy granulation tissue does not bleed easily.
Dark granulation tissue can be a sign of infection, ischemia, or poor perfusion.
Finally epithelial cells resurface the injury.
Epithelialisation happens faster when wounds are kept moist and hydrated.
Generally, when occlusive or semi-occlusive dressings are applied within 48 hours after injury, they will maintain correct tissue humidity to optimize epithelialization.
what happens in the remodelling stage
> Collagen is remodelled from type III to type I and the wound fully closes.
The cells that had been used to repair the wound but which are no longer needed are removed by apoptosis, or programmed cell death.
The collagen laid down during the proliferative phase, it is disorganized and the wound is thick.
Collagen is remodelled into a more organized structure along lines of stress, thereby increasing the tensile strength of the healing tissues. Fibroblasts secrete matrix metalloproteinases. The enzymes facilitate remodelling of type III collagen to type I collagen.
Generally, remodelling begins about 21 days after an injury and can continue for a year or more.
Even with cross-linking, healed wound areas continue to be weaker than uninjured skin, generally only having 80% of the tensile strength of unwounded skin.
what happens at the haematoma formation stage
When a bone is fractured, blood vessels in the vicinity of the fracture rupture, leading to the formation of a hematoma, or a blood clot, at the site of the injury. The hematoma serves as a temporary scaffold for the formation of new bone tissue.
what happens at the inflammatory stage in bone healing
In this phase, inflammatory cells, such as neutrophils and macrophages, migrate to the site of the fracture to remove dead tissue and debris and to initiate the healing process. Growth factors and cytokines released by these cells stimulate the proliferation of cells involved in bone repair.
what happens in the repair phase
During this phase, specialized cells called chondroblasts produce a soft callus, composed of collagen and cartilage, which bridges the gap between the broken bone ends. This soft callus provides initial stability to the fracture site and serves as a framework for the deposition of new bone tissue.
what happens at the remodelling stage of bone healing
Over time, the soft callus is gradually replaced by hard callus, or woven bone, through a process called endochondral ossification. Osteoblasts, cells responsible for bone formation, deposit new bone tissue, which gradually remodels and reshapes the fracture site to restore the bone’s original structure and strength. This phase can take several months to complete and may continue for years, during which the bone undergoes continuous remodeling in response to mechanical stress.
