Pathology by Inam Danish Chapter # 4 Cell Repair and healing

1. Pathlogy
Topic: Cell Repair Presented to:
Sir Bilal
Group members:
Shafa Ashfaq 224422
Ayesha Imran 224442
Yasra Azam 224444
Maliaka Shafiq 224425
Hamza Iftikhar 224430

2. Cell repair
Defination: It is the process in which damage or destroyed cells are replaced by
viable cells or undamaged cells .
Example:
 Healing of a punctured Xenopus oocyte.
 Regrowth of damaged axons in neurons.
 Regeneration of flagella in Chlamydomonas.
Compound used in repairing process:
Hyaluranic acid, a naturally occurring compound, awakens stem cells to repair damaged
muscle.
Incapaple cells :
Permanent cells are cells that are incapable of regeneration.

3. Process: There are 2 process involves in cell repair .
 By regeneration
 By replacement of connective tissues.
REGENTRATION
Defination:
Regeneration is the natural process of replacing or restoring damaged or missing cells,
tissues, organs, and even entire body parts to full function in plants and animals.
Examples:
As adults, humans can regenerate some organs, such as the liver.

4. Capable cells: Only 3 groups have their regenrative capacity.
1.continous dividing cells
2.Quiescent cells3.
Non _dividing cells
Continous diving cells :-
These cells poliferate throughout life,replacing those cells that are continuously dying.
Examples:
• Stratied squamous epithelial of skin
• oral cavity
• cervix
• Cubiodal epithelium of exocrine glands like salivary glands
• pancreas , billiary tract .
• Columnar epithelium of GIT ,uterus,follapain tubes
• Hematopoietic cells of bone marrow .

6. Quiescent (stable) cells
Definition:
Quiescence is a cellular state in which a cell remains out of the cell cycle but retains the
capacity to divide. However,these can undergo rapid division in response to a variety of
stimuli and are thus capable of reconstitution of the tissue of origin.
Examples:.
Parenchymal cells of liver, kidney and pancreas. Mesenchymal cells e.g. smooth muscle,
cartilage, connective tissue, fibroblast and vascular endothelial cells.
Examples of quiescent cells include many adult stem cells, progenitor cells, fibroblasts,
lymphocytes, hepatocytes and some epithelial cells.

7. Permanent (non-dividing) cells
Definition:
Permanent cells are defined as the cells that are incapable of division and regeneration.If they are
destroyed,the loss is permanent and repair occurs only by the connective tissue (i.e. by scar
formation).These cells are unable to replicate in postnatal life.Nervous cells, also termed neurons,
together with skeletal muscle and cardiac cells, are included in this group, which traditionally
identifies the human tissues that are incapable of spontaneous regeneration.
Examples:
• Nerve cells(neurons)
• Cardiac muscles
• Skeletal muscles

8. Control of cell growthCellular:
proliferation is largely regulated by biochemical factors produced in the local micro-
environment that can either stimulate or inhibit cells growth. These biochemical factors that
stimulate growth are called Growth factors while those that inhibit growth are called
Inhibitory factors.

10. Growth factor
A substance made by the body that functions to regulate cell division and cell survival. Some
growth factors are also produced in the laboratory and used in biological therapy.* Epidermal
growth factor* Platelet derived growth factor* Fibroblast growth factor* Vascular growth
factor* Cytokines e.g interleukin 1and tumor necrosis factor Inhibitory factor Factor that
inhibits the growth are called inhibitory factors .
Examples:
 A pleiotropic protein,
 Participating in inflammatory
 Immune responses.

11. Transforming growth factors F3
Tumor necrosis factors Repair by connective tissue (scar formation)Repair by connective
tissue involves the influx of debris-removing inflammatory cells, formation of granulation
tissue (a substance consisting of fibroblasts and delicate capillaries in a loose extracellular
matrix) and conversion of said granulation tissue into fibrous tissue that is remodeled over
time to form a scar.
What is process of scar formation?
When the skin is wounded, the tissues break, which causes a protein called collagen to be
released. Collagen builds up where the tissue is damaged, helping to heal and strengthen the
wound. New collagen continues forming for several months and the blood supply increases,
causing the scar to become raised and lumpy.

13. PHASES OF REPAIR BY SCAR FORMATION
Preparation:
The area of injury is prepared for scar formation by removal of the inflammatory
exudate by the lymphatics.
•INGROWTH OF GRANULATION TISSUE:
Granulation tissue forms and fills the injured area while the necrotic debris is being
removed. Granulation tissue is highly vascularization connective tissue composed of
newly formed capillaries, proliferation fibroblastic and residual inflammatory cells. On
gross examination, granulation tissue is soft and pink because of numerous
capillaries.Microscopic examination shows thin walled capillaries lined by endothelium
and surrounded by fibroblasts.

14. PRODUCTION OF FIBRONECTIN:
Fibronectin is a glycoprotein that plays key role in the formation of granulation
tissue and is present in large amounts during wound healing.In early phases,it is
derived from plasma, but later it is synthesized by fibroblasts, macrophages and
endothelial cells in granulation tissue.

16. •COLLAGENIZATION:
Collagen is the major fibrillary protein of connective tissue is
synthesized by fibroblast and is responsible for much of the tensile
strength of scar tissue.The terms fibrous tissue and scar tissue.The
terms fibrous tissue and scar tissues are synonymous with collagen.
MATURATION OF SCAR:
A young scar consists of Granulation tissue and abundant collagen together
with capillaries and fibroblasts.It appears pink on gross examination because
of the vascularity.As the scar matures,the amount of collagen increase and
the scar become less cellular and less vascular.The mature scar is composed
of an avascular, poorly cellular mass of collagen, and is white on gross
examination.

17. .
CONTRACTION AND STRENGTHENING
It is the final phase of scarformation. Contraction decrease the size of scar
and enables the surviving cells of the organ to function with maximum
effectiveness.