Embed Size (px)
Citation preview
TISSUE RENEWAL, REGENERATION &
REPAIR
JOMIN GEORGELECTURER
FACULTY OF HEALTH INFORMATION MANAGEMENT
Email: [email protected]
Healing
• The word healing, used in a pathological
context, refers to the body’s replacement of
destroyed tissue by living tissue.
Regeneration
• Regeneration, the replacement of lost/
damaged tissue by tissues of similar in
type.
• OCCURS ONLY IN TISSUES WITH
REGENERATIVE ACTIVITY.
Repair
• A process in which lost/
damaged tissue replaced by
fibrous tissue or scar.
• Eg. Healed myocardial
infarction.
Cell Proliferation
An increase in the number of
cells as a result of cell
growth and cell division.
Control of Normal Cell Proliferation
• In adult tissues the size of cell populations is determined
• The rates of cell proliferation.
• differentiation, and death by apoptosis
Conditions…
• Cell proliferation can be stimulated by physiologic and pathologic
conditions.
• The proliferation of endometrial cells under estrogen stimulation
during the menstrual cycle.
• The thyroid stimulating hormone–mediated replication of cells of
the thyroid that enlarges the gland during
• pregnancy .
TISSUE PROLIFERATIVE ACTIVITY
• According to regenerative capacity of the cell, the tissue
of the body can divide into 3 groups.
nondividing
(permanent tissues)
quiescent (stable tissues)
continuously dividing (labile
tissues)
Continuously dividing tissues
• These Cells proliferate throughout life, replacing
those that are destroyed.
• Stratified squamous epithelia of the skin, oral cavity,
vagina, and cervix; the lining mucosa of all the
excretory ducts of the glands of the body (e.g.,
salivary glands, pancreas, biliary tract);
Quiescent tissues
• Normally have a low level of replication;
however, cells from these tissues can undergo
rapid division in response to stimuli .
• Thus capable of reconstituting the tissue of
origin.
• Eg:- are the parenchymal cells of liver, kidneys,
and pancreas
Examples • Smooth muscle
cells, chondrocytes,
and osteocytes are
quiescent in adult
mammals but
• Proliferate occurs in
response to injury.
partial hepatectomy
Permanent tissues
These are non-dividing cells. If lost, permanent cells
cannot be replaced, because they don’t have the
capacity to proliferate. For example: adult neurons,
striated muscle cells, and cells of the lens.
Cell cycle
• The cell cycle, or cell-division cycle, is the series of
events that take place in a cell leading to its division and
duplication (replication) that produces two daughter cells.
Phases of the Cell Cycle
The two main divisions of the cell cycle are
interphase and mitosis.
Phases
• In eukaryotic cells, this process includes of four distinct phases.
• Mitosis phase (M),
• Gap 1 phase (G 1),
• Synthesis phase (S), and interphase
• Gap 2 phase (G 2).
Interphase
• During this segment of the cell cycle, a cell doubles its cytoplasm and
synthesizes DNA.
• It is estimated that a dividing cell spends about 90-95 percent of its
time in this phase.
• G1 phase: The period prior to the synthesis of DNA.
• In this phase, the cell increases in mass and organelle number
in preparation for cell division.
• Animal cells in this phase are diploid, meaning that they have two sets
of chromosomes.
• S phase: The period during which DNA is
synthesized.
• The chromosome content is doubled in this phase.
• G2 phase: The period after DNA synthesis .
• prior to the start of mitosis.
• The cell synthesizes additional proteins and continues to increase in
size.
The Cell Cycle
• Small Growth
• Metabolism
• Preparation for DNA
SynthesisJust finished division
Replication of
DNA and
Centrosomes
• More growth• Protein synthesis• Preparation for
division
Stages of Mitosis
In mitosis and cytokinesis, the contents of the dividing cell are equally distributed between two daughter cells. Mitosis has four phases:
• Prophase
• Metaphase
• Anaphase
• Telophase.
• Prophase: In this stage, changes occur in both
the cytoplasm and nucleus of the dividing cell.
• The chromatin condenses into discrete
chromosomes.
• The chromosomes begin to migrate toward the
cell center. The nuclear envelope breaks down
and spindle fibers form at opposite poles of the
cell.
• Metaphase: In this stage, the nuclear
membrane disappears completely.
• The spindle fully develops and the
chromosomes align at the metaphase plate
(a plane that is equally distant from the two
poles).
• Anaphase: In this stage, paired
chromosomes (sister chromatids) separate
and begin moving to opposite ends (poles)
of the cell. Spindle fibers not connected to
chromatids lengthen and elongate the cell.
• Telophase: In this stage, the chromosomes are cordoned off
into distinct new nuclei and the genetic content of the cell
is divided equally into two parts.
• Cytokinesis begins prior to the end of mitosis and
completes shortly after telophase.
• Cell wall for plants.
• Cleavage furrow forms
• What are the phase mitosis ?
• What is the function of checkpoints in cell cycle?
• In which phase the chromosomes aligned as equator line?
• What are the different types of tissue classification ?
