Page 68 - Concise Pathology for Exam Preparation ( PDFDrive )

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Healing and Repair

Q. Define repair.

Ans. Restoration of tissue architecture and function after injury is termed repair.
It may occur in two ways:
1. Regeneration: The injured tissue reverts to normal after replacement of damaged
components by the active proliferation of residual cells as well as maturation of stem cells.
2. Healing with scar formation: If the individual tissue is incapable of complete restoration
to original state or if there is severe damage to the supporting structures, repair occurs by
a laying down of connective tissue. This is labelled 'healing with scar formation'.

Q. Define fibrosis.

Ans. A term used to describe extensive deposition of collagen that occurs in parenchymal
organs as a consequence of chronic inflammation . Fibrosis develops in a tissue space
by organization of the inflammatory exudate occupying the tissue space.

Q. Classify different types of cells.

Ans. Cells are divided into three groups based on their ability to repair themselves:
1. Labile/continuously dividing cells: Cells which replenish their damaged/injured
counterparts by continuous division and maturation of cells from the stem cell pool,
eg, surface epithelial cells (skin, oral cavity, vagina and cervix), haematopoietic cells in
bone marrow and columnar epithelium of GIT.
2. Stable/quiescent cells (facultative mitotic cells): Cells of this type are in G 0 stage of
cell cycle, and do not replicate actively in their normal state; however, they are capable
of proliferating in response to loss of tissue mass, eg, parenchymal cells of solid organs
(liver, kidneys and pancreas), endothelial cells, fibroblasts, smooth muscle cells, chon-
drocytes and osteocytes.
3. Permanent/nondividing cells: Terminally differentiated cells, which are nonprolifera-
tive and incapable of regenerating, eg, neurons, skeletal muscle and cardiac muscle
cells.

Q. What are stem cells?
Ans. Stem cells are cells with self-renewal capacity. They are characterized by asymmetric
replication (a property of stem cells by virtue of which , after every cell cycle, some of the
daughter cells retain their self-renewal capacity while the others enter a differentiation
pathway, and are converted into a mature nondividing population). Stem cells may be
• Embryonic stem cells: Stem cells that are isolated from embryos are called embryonic
stem cell (ES; Fig. 3 .1). These are the m ost undifferentiated stem cells located in the
inner cell mass of the blastocyst. They can give rise to any type of cell in the body and
are therefore also called totipotent stem cells.
• Adult stem cells have a markedly restricted differentiation capacity and are usually
lineage specific. Adult stem cells located outside the bone marrow and in the tissue are

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