2. INTRODUCTION
• Injury to a tissue may result in cell death
and tissue destruction
• A wound is a disruption of the anatomic
structure and function in any body part.
• Healing on the other hand is a cell
response to injury in an attempt to restore the
normal structure and function .
3. • Healing Involves 2 distinct processes :
• – Regeneration
• – Repair
• At times both the processes take place simultaneously
4. Regeneration
When healing takes place by proliferation of
parenchymal cells and usually results in
complete restoration of the original tissues.
5. • Regeneration of any type of parenchymal cell involves following two
processes :
• Proliferation of the original cells from the margin of the injury which
migrates so as to cover the gap
• Proliferation of the migrated cells with subsequent differentiation
and maturation so as to reconstitute the original tissue
6. REPAIR
•When healing takes place by proliferation of
connective tissue resulting in fibrosis and
scarring
7. Cell cycle : Is defined as the period between
two successive cell divisions
8.
9. • Cell cycle and the proliferative capacity of different cells types :
• Cells are of 3 types depending on their capacity to divide :
Labile cells
Stable cells
Permanent cells
10. •Labile cells
Continue to multiply throughout life under normal physiologic
conditions.
Surface ep cells of epidermis, alimentary tract, respiratory tract,
urinary tract, vagina,cervix, uterine endometrium, hematopoietic
cells of B/M, cells of lymph node and spleen
11. •Stable cells- Decrease or lose their ability to proliferate after
adolescence but retain capacity to multiply in response to stimuli
throughout adult life
Parenchymal cells of organs like
liver, pancreas, kidneys,
adrenal and thyroid
Mesenchymal cells like
smooth muscle cells,
fibroblasts, vascular
endothelium, bone ,
cartilage cells
12. •Permanent cells- Cells lose their ability to proliferate around
the time of birth.
Neurons of nervous system,
skeletal muscle, cardiac muscle
cells
13. •Molecular events in cell growth :
• Although many chemical mediators affect cell growth POLYPEPTIDE
GROWTH FACTORS… are most imp for growth.
• GF have a Pleiotropic role :
Cellular proliferation and differentiation :
affecting the expression of the genes involved in
growth control pathways
• Tissue remodeling
14. • REPAIR
• Repair is the replacement of injured tissue by fibrous tissue.
• Two processes are involved in repair:
1. Granulation tissue formation; and
2. Contraction of wounds.
• Repair response takes place by participation of
mesenchymal cells (consisting of connective tissue stem
cells,fibrocytes and histiocytes), endothelial cells,
macrophages,platelets, and the parenchymal cells of the injured
organ.
15. • Granulation Tissue Formation
The term granulation tissue derives its name from slightly granular
and pink appearance of the tissue.
16. • Each granule histologically corresponds to
proliferation of new small blood vessels which
are slightly lifted on the surface by a thin
covering of fibroblasts and young collagen .
17.
18.
19. •WOUND HEALING
• Healing of skin wounds provides a classical example of combination
of regeneration and repair.
• Wound healing can be accomplished in one of the following two
ways:
• Healing by first intention (primary union)
• Healing by second intention (secondary union).
20. •Healing by First Intention (Primary Union)
• This is defined as healing of a wound which has the following
characteristics:
• i) clean and uninfected;
• ii) surgically incised;
• iii) without much loss of cells and tissue; and
• iv) edges of wound are approximated by surgical sutures.
21. Primary union of skin wounds. A, The incised wound as well as suture track on either side are filled
with blood clot and there is
inflammatory response from the margins. B, Spurs of epidermal cells migrate along the incised
margin on either side as well as around the suture
track. Formation of granulation tissue also begins from below. C, Removal of suture at around 7th
day results in scar tissue at the sites of incision
and suture track.
22. • Thus, the scar formed in a sutured wound is neat due to close
apposition of the margins of wound; the use of adhesivetapes avoids
removal of stitches and its complications.
23. Healing by Second Intention (Secondary
Union)
This is defined as healing of a wound having the following
characteristics:
•i) open with a large tissue defect, at times infected
•ii) having extensive loss of cells and tissues
•iii) the wound is not approximated by surgical
sutures but is left open.
24. •The basic events in secondary union are similar to
primary union but differ in having a larger tissue
defect which has to be bridged. Hence healing takes
place from the base upwards as well as from the
margins inwards.
• The healing by second intention is slow and results
in a large, at times ugly, scar as compared to rapid
healing and neat scar of primary union.
25. Secondary union of skin wounds. A, The open wound is filled with blood clot
and there is inflammatory response at the junction of
viable tissue. B, Epithelial spurs from the margins of wound meet in the middle
to cover the gap and separate the underlying viable tissue from
necrotic tissue at the surface forming scab. C, After contraction of the wound,
a scar smaller than the original wound is left.
26.
27. • Factors Influencing Healing
• A. LOCAL FACTORS:
• 1. Infection is the most important factor acting locally which
delays the process of healing.
• 2. Poor blood supply to wound slows healing.
• 3. Foreign bodies including sutures interfere with healing
• 4. Movement delays wound healing.
• 5. Exposure to ionising radiation delays granulation tissue formation.
• 6. Exposure to ultraviolet light facilitates healing.
• 7. Type, size and location of injury determines whether healing takes
place by resolution or organisation.
28. • B. SYSTEMIC FACTORS:
• 1. Age. Wound healing is rapid in young and somewhat slow in aged and
debilitated people due to poor blood supply to the injured area in the latter.
• 2. Nutrition. Deficiency of constituents like protein, vitamin C (scurvy) and
zinc delays the wound healing.
• 3. Systemic infection delays wound healing.
• 4. Administration of glucocorticoids has anti-inflammatory
effect.
• 5. Uncontrolled diabetics are more prone to develop infections and hence
delay in healing.
• 6. Haematologic abnormalities like defect of neutrophil functions
(chemotaxis and phagocytosis), and neutropenia and bleeding disorders
slow the process of wound healing.
30. • Primary union of fractures occurs in a few special situations when
the ends of fracture are approximated as is done by application of
compression clamps. In these cases, bony union takes place with
formation of medullary callus without periosteal callus formation.
The patient can be made ambulatory early but there is more
extensive bone necrosis and slow healing.
• Secondary union is the more common process of fracture healing
when plaster casts are applied for immobilization. Though it is a
continuous process, secondary bone union is described under the
following 3 headings:
32. Fracture healing. A, Haematoma formation and local inflammatory response at the
fracture site. B, Ingrowth of granulation tissue
with formation of soft tissue callus. C, Formation of procallus composed of woven bone
and cartilage with its characteristic fusiform appearance and
having 3 arbitrary components—external, intermediate and internal callus. D,
Formation of osseous callus composed of lamellar bone following
clearance of woven bone and cartilage. E, Remodelled bone ends; the external callus
cleared away. Intermediate callus converted into lamellar
bone and internal callus developing bone marrow cavity.
34. • Healing of Muscle
• All three types of muscle fibres have limited capacity to regenerate.
• SKELETAL MUSCLE. The regeneration of striated muscle is similar to
peripheral nerves. On injury, the cut ends of muscle fibres retract but
are held together by stromal connective tissue. The injured site is filled
with fibrinous material, polymorphs and macrophages. After clearance
damaged fibres by macrophages, regeneration of muscle fibres can
occur:
35. • SMOOTH MUSCLE. Non-striated muscle has limited
• regenerative capacity e.g. appearance of smooth muscle in the
arterioles in granulation tissue. However, in large destructive lesions,
the smooth muscle is replaced by permanent scar tissue.
• CARDIAC MUSCLE. Destruction of heart muscle is replaced by
fibrous tissue.
