Tissue repair Flashcards
What is repair?
Restoration of tissue architecture and function
What determines a tissues ability to repair itself?
The presence of stem cell as well as the intrinsic capability of the cells to proliferate
Explain what angiogenesis is and detail the process.
Angiogenesis is the process by which new blood vessels are made from the existing ones
Vasodilatation and increased permeability of the blood vessel take place and then the pericytes separate to expose the basement membrane.
VEGF diffuses through the basement membrane and attaches to the endothelial cells.
One cell takes the lead and is known as the TIP cell, and it secretes chemicals which break down the basement membrane.
The tip cell then moves towards the site of injury followed by the other endothelial cells.
This is also brought about by Matrix Metalloproteinases which degrade the ECM to permit remodeling
Behind the tip cells, endothelial cells begin to proliferate with the help of VEGF-A and FGF-2
Remodeling takes place forming a lumen between the endothelial cells and it is brought about by angiopoietins 1 and 2
The same process is happening in another blood vessel and their tip cells fuse and they remodel into a capillary tube.
What does TGF-B do?
Stimulates fibroblast migration and proliferation
increases synthesis of collagen and fibronectin
inhibits metalloproteinases
Decreases degradation of ECM
Inhibits lymphocyte proliferation and leukocyte
activation
Limits and terminates inflammatory response
Explain healing by primary intention
Healing by primary intention is when the wound edges come together–like what happens when two wound margins are stitched or sutured together.
When this happens, stem cells in the epidermis, or uppermost layer of skin are brought close together and can regenerate the damaged tissue near the surface of skin–leaving a minimal scar.
Explain healing by secondary intention
Healing by secondary intention occurs when the wound edges are too far from one another–this can be consequence of significant tissue loss or if there’s an object embedded in the wound that prevents the edges from coming together.
Examples of healing by secondary intention include tooth extraction sockets or severe burn injuries.
Since the stem cells in these wounds do not approximate, the wound is replaced primarily by connective tissue that grows from the base of the wound upwards.
Explain healing by tertiary intention
Healing by tertiary intention, or delayed closure, is when a wound is cleaned and purposefully left open due to a high likelihood of being contaminated by bacteria–like during a dog bite injury.
If these wounds are closed too early by primary intention they can trap bacteria inside the wound–leading to an abscess or walled off infection.
Instead, these wounds are left open, cleaned, and observed for several days before they’re closed by primary intention or left open to heal by secondary intention.
Explain the steps involved in wound healing
1st step is hemostastis
