Tissue healing

Question 1

Haemostasis=

Answer 1

Is a protective response to the rupture of blood
vessels. It prevents excess blood loss and important for tissue repair. It is a process that limits
excessive bleeding following injury.
There are three stages.

Question 2

What are the stages of haemostasis?

Answer 2

1. Vascular spasm= When a blood vessel is damaged, it releases chemicals that cause the smooth muscle in its walls to contract. This reduces blood flow and limits blood loss. The spasm lasts about 20-30 minutes.
2. Platelet formation= Platelets in the blood become sticky when they encounter exposed collagen in the damaged vessel. They form a temporary plug by sticking to the damaged area and releasing chemicals (e.g., ADP, serotonin) that enhance the process. However, this plug is fragile and only works for small injuries.
3. Coagulation (blood clotting)
   Two pathways (intrinsic and extrinsic) activate a series of chemical reactions that form prothrombin activator. This converts prothrombin into thrombin, which then transforms fibrinogen (a soluble protein) into fibrin (an insoluble mesh). The fibrin mesh stabilizes the platelet plug, creating a strong clot to stop bleeding.

Question 3

What are the stages of soft tissue healing?

Answer 3

Haematoma (Day 0):
When tissue is injured, blood clots form to stop bleeding and create a barrier against bacteria. The clot stabilizes as fibrin forms a mesh, reducing blood loss and beginning the healing process.

Scab Formation (Day 0–3):
The blood clot dries to form a scab, protecting the wound from moisture and infection. White blood cells, like neutrophils and macrophages, clear debris and fight bacteria. Inflammatory responses depend on the size and cleanliness of the wound.

Granulation Phase (Day 4–14):
New capillaries grow into the wound, and fibroblasts produce collagen and other substances to replace the clot. This granulation tissue helps pull the wound together and stabilizes the area.

Regeneration and Remodelling (Day 14–2 Years):
New skin cells regenerate, and the scab falls off. Fibroblasts die or become inactive, leaving scar tissue that looks different due to the alignment of blood vessels and collagen.

Question 4

What are the stages of bone repair?

Answer 4

Haematoma (Day 0–2):
Blood vessels in the bone and periosteum break, causing bleeding and clot formation. Inflammation follows, making the area swollen, red, and painful.

Soft Callous (Day 2–4):
Granulation tissue forms as new blood vessels grow. Fibroblasts produce collagen, and chondroblasts create cartilage. This forms a flexible mass (soft callous) that connects the broken bones and acts like a natural splint.

Hard Callous (Up to 6 Weeks):
The soft callous is replaced with spongy bone as osteoblasts build and osteoclasts remove excess tissue. The area becomes more rigid and calcified.

Remodelling (Up to Several Years):
Osteoblasts and osteoclasts remodel the hard callous into spongy or dense bone as needed. Over time, the repaired bone becomes identical to the original tissue, though full restoration may take years.