healing by first and second intention.

1. Wound Healing
And
Factors Affecting Wound
Healing
1

2. Wound: injury to living tissue by cut, blow or
other impact, leads to loss of cells and tissues.
Healing: process of replacement of dead
tissue by living tissue. 2

3. Processes of healing:
❖ Regeneration
-loss tissue is replaced by tissue of similar
type.
- complete restoration of lost or damaged
tissue.
❖ Repair
-loss/damaged tissue replaced by fibrous
tissue or scar.
3

4. 4

5. According to regenerative capability, 3 types
of tissue:
1. Labile tissue- chance of regeneration
excellent. E.g. epithelium of skin and GIT.
2. Stable tissue- chance of regeneration
good. E.g. parenchymal cell of liver and
kidney.
3. Permanent tissue- No
regeneration(scarring). E.g. neurons and
cardiac muscles.
5

6. 6
Types of wound
healing
Healing by first
intention/primary
union
Healing by second
intention/secondary
healing

7. I. Healing by first intention
-healing of clean, uninfected incised
wound; particularly planned surgical
incisions.
-re-epithelization by regeneration to
close the wound occurs,
with formation of relatively thin scar.
-following sequence of events take place:
7

8. 1. First 24 hrs
-formation of blood clot between suture
margins.
-formation of scab by dehydration of external
surface of clot.
-neutrophil appear at the margin of incision
which clean out debris.
-basal cell of epidermis shows mitotic activity.
8

9. 9

10. 2.Two days:
– Neutrophils are replaced by
macrophages.
– The epithelial cells fuse in the midline
below the surface scab and epithelial
continuity is re-established
in the form of a thin continuous surface
layer.
10

11. 3. Three to seven days:
– Granulation tissue begins to invade incision
space.
It progressively grows into the incision
space/wound
and fills the wound area by 5–7 days. Collagen is
progressively laid down.
– Surface epidermis achieves its normal thickness
and differentiation. It matures with surface
keratinization.
– Acute inflammatory response begins to subside. 11

12. 4. Ten to fourteen days:
– Leukocytic infiltration, edema, and angiogenesis
disappear during the second week.
– Increased accumulation of collagen and
regression of vascular channels.
-The granulation tissue scaffolding is converted
into a pale, avascular scar.
-Wound normally gains about 10% strength of
normal skin. Further fibroblast proliferation
occurs with collagen deposition.
12

13. 5.Weeks to months:
– The scar appears as acellular connective
tissue covered by intact epidermis and without
inflammatory infiltrate.
– Collagen deposition along the line of stress
and wound gradually achieves maximal 80% of
tensile strength of normal skin.
13

14. 14

15. II. Healing by second intention
-occurs in open wound, particularly in site of
significant loss of tissue, necrosis, chronic
inflammation or infection.
- basic mechanism of healing by primary and
secondary union are similar.
FEATURES:
-Larger wounds show more exudate and
necrotic tissue.
15

16. -The clot or scab formed at the surface of
wound is large. Full epithelialization of the
wound surface is slow because of the larger
gap.
-Severe inflammatory reaction because of
larger defect and greater necrotic tissue.
-The larger defect requires more amount of
(abundant) granulation tissue.
-Extensive deposition of collagen with
substantial scar formation. 16

17. 17
-Wound contraction occurs, mediated by
myofibroblasts.

18. Factors affecting wound healing
A. Local factors
1. Infection
2. Poor blood supply
3. Foreign bodies
4. Movement
5. Ionizing radiation
6. Ultraviolet rays
7. Type,size and location of injury
18

19. B. Systemic factors
1. Age
2. Nutrition
3. Systemic infection
4. Administration of glucocorticoids
5. Uncontrolled diabetes
6. Haematologic abnormalities
7. Immune status
8. Smoking
19