Tissue renewal

TISSUE RENEWAL,
REGENERATION &
REPAIR
JOMIN GEORGE
LECTURER
FACULTY OF HEALTH INFORMATION MANAGEMENT
Email: jomin.george@bothouniversity.ac.bw

Healing
• The word healing, used in a pathological
context, refers to the body’s replacement of
destroyed tissue by living tissue.
Jomin.george@bothounivesity.ac.bw

Processes of healing
Regeneration Repair

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 Division

What you think if you can
clone yourself?

Why cell divide ??

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.

THE CELL CYCLE/ LIFE CYCLE.
Not Dividing
Interphase
Dividing

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.

G0
A resting phase where the cell has left the
cycle and has stopped dividing.

The cell cycle have
checkpoints
Check Points

Summary of interphase.

The Cell Cycle
• Small  Growth
• Metabolism
• Preparation for DNA
SynthesisJust finished
division
Replication of
DNA and
Centrosomes
• More growth
• Protein synthesis
• Preparation for
division

Chromosome
JOMIN.GEORGE@BOTHOUNIVESITY.AC.BW

JOMIN.GEORGE@BOTHOUNIVESITY.AC.BW

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

I
D
E
N
T
I
F
Y

• 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 ?

Tissue renewal

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