Cell Repair Flashcards
Which are the two types of reactions to repair damaged tissues?
-Regeneration by proliferation of residual (uninjured) cells and maturation of tissue stem cells.
-The deposition of connective tissue to form a** scar**
What is Regeneration?
** Some tissues are able to replace the
damaged components and essentially return to a normal state**. occurs by proliferation of cells that survive the injury
and retain the capacity to proliferate In other cases, tissue stem cells may contribute to the restoration.
How is the process of Tissue deposition (Scar formation)?
When injured tissues are incapable of complete restitution, or if the supporting structures of the tissue are severely damaged, repair occurs by the laying down of connective (fibrous) tissue.
Restoring the function of tissue with a Fibrus Scar is normal?
No, but it provides enough stability that the injured tissue is usually able to function.
Define Fibrosis
Most often used to describe the extensive deposition of collagen that occurs in the lungs, liver, kidney, and other organs as a consequence of chronic inflammation, or in the myocardium after extensive ischemic necrosis (infarction).
Cell proliferation involved during tissue repair?
-Remnants of the injured tissue (which attempt to restore normal structure)
-Vascular endothelial cells (to create new vessels that provide the nutrients needed for the repair process)
-**Fibroblast **(source of the fibrous
tissue that forms the scar to fill defects that cannot be corrected by regeneration)
Examples of Liable tissue (cells are constantly being lost and must be continually replaced by new cells that are derived from tissue stem cells and rapidly proliferating immature progenitors)
hematopoietic cells in the bone marrow and many surface epithelia, such as the basal layers of the squamous epithelia of the skin, oral cavity, vagina, and cervix; the cuboidal epithelia of the ducts draining exocrine organs (e.g., salivary glands, pancreas, biliary tract); the columnar epithelium of the gastrointestinal tract, uterus, and fallopian tubes; and the transitional epithelium of the urinary tract
Examples of Stable tissues (cells
that are normally in the G0 stage of the cell cycle and hence not proliferating, but they are capable of dividing in response to injury or loss of tissue mass.)
The parenchyma of most solid organs, such as liver, kidney, and pancreas. Endothelial cells, fibroblasts, and smooth muscle cells
Examples of Permanent tissues ( terminally differentiated nonproliferative cells)
The majority of neurons and cardiac muscle cells.
Which cells produce Growth factors in the site of damage
-Cells near the site of damage
- Macrophages (The most important sources) that are activated by the tissue injury.
-Epithelial
-Stromal cells*
- highly heterogeneous class of connective tissue cells that build the infrastructure
stromal cells are heterogeneous class of connective tissue cells that bu
Mechanism of Growht Factors
Several growth factors bind to ECM proteins and are displayed at the site
of tissue injury at high concentrations, All growth factors activate signaling pathways that ultimately induce changes in gene expression that drive cells through the cell cycle and support the biosynthesis of molecules and organelles that are needed for cell division.
The most important stem cells for regeneration after injury are?
Tissue stem cells.
These stem cells live in specialized niches, and it is believed that injury triggers signals in these niches that activate quiescent stem cells to proliferate and differentiate into mature cells that repopulate the injured tissue
Mechanisms of Tissue Regeneration in Epithelia of the intestinal tract and skin
Injured cells are rapidly** replaced by proliferation of residual cells and differentiation of cells derived from tissue stem cells**, providing the underlying basement membrane is intact. The residual epithelial cells produce the growth factors involved in these processes. The newly generated cells migrate to fill the defect created by the injury, and tissue integrity is restored
Mechanisms of Tissue Regeneration in parenchymal organs
The mechanisms underlying this response
are not understood, but they likely involve local production of** growth factors and interactions of cells with the ECM.**
Tissue regeneration can occur in parenchymal organs whose cells are capable of proliferation, but with the
exception of the________ this is usually a limited process.
Liver
Pancreas, adrenal, thyroid, and lung have some regenerative capacity
