1. It is characterized by the process of regeneration of the damaged tissue by the cells of the same type and replacement of the lost tissue with the connective tissue.
2. Regeneration refers to proliferation of cells and tissues to replace lost structures.
3. Due to regeneration their is a complete restitution of lost or damaged tissue.

HEALING OF PRIMARY INTENTION :-

1.] The healing of a clean uninfected wound is called healing by first primary union.

2.] Vitamin C is required for the conversion of tropocollagen to collagen due to hydroxylation of lysin and proline residues providing stability to collagen molecules.

3.] It involves following changes :

• Day 0 (when the wound has formed) : Presence of blood clot in the incision.
• Day 1 (within 24 hours) : Neutrophilic infiltration + blood clot.
• Day 2 (24 to 48 hours): Neutrophils + blood clot + continuous thin epithelial layer.
• Day 3 : Macrophages replaces neutrophils. Appearance of granulation tissue, type lll collagen deposition begins but not bridge the incision.
• Day 5 : Abundant granulation tissue (collagen fibrils bridge the incision, neurovascularisation is maximum, full epithelial thickness with surface keratinization).
• End of 2 week : Accumulation of collagen, fibroblast proliferation.
• 1 month : Replacement of collagen type lll with collagen type l (has greater tensile strength) due to the action of collagenase enzyme.

HEALING BY SECONDARY INTENTION :-

1.] During healing by secondary intention or secondary union, inflammatory reaction being more intense, granulation tissue is abundant and a large scar is formed.

2.] The scar decreases in size after sometime; this is called as scar contraction.

3.] Wound strength is 10% after 1 week, it increases rapidly during next 4 week and become 70% at the end of 3 month.

4.] The tensile strength of wound jeep on increasing as time progresses.

5.] Collagen degradation is important for tissue remodeling, angiogenesis and cancer metastasis.

6.] Zinc deficiency is associated with impaired wound healing.

7.] The chief cell responsible for scar contraction is myofibroblast.

Process of Wound Healing (Below Figure is taken(Educational Purpose) from Research article of Shinichi Hayashi et al (DOI: 10.1007/82_2012_305).

COMPLICATIONS :–

1.] During wound healing, complications can arise from :-

• Delayed wound healing.
• Deficient scar formation.
• Excessive formation of the repair components.
• Formation of contractures.

TREATMENT :-

Cleaning the wound:-

The wound is often cleaned when the dressing is changed, normally using a saline (salt) solution.

Debridement :-

When treating chronic wounds, doctors or nurses often remove dead or inflamed tissue. This is known as debridement. The tissue is removed using instruments such as tweezers, a sharp spoon-like instrument called a curette, or a scalpel. An enzyme-based gel is sometimes applied too, to help clean the wound.

The wound can also be cleaned using a high-pressure water jet. Another form of debridement involves the use of a certain species of maggots (fly larvae) that are specially bred for medical purposes. The maggots are placed on the wound, either as they are or in a pouch. They remove dead tissue and fluid from the wound.

Because debridement is often painful, a local anesthetic is used to numb the wound beforehand, for instance using an ointment. If more severe pain is expected, painkillers can also be taken before treatment. Larger wounds are sometimes cleaned under general anesthetic.

Wound dressings

Once the wound has been cleaned, it is covered with a dressing. Most wounds are kept moist, for instance with moist compresses. But the following kinds of dressings can be used instead:

• Films
• Gauze
• Hydrogel dressings
• Hydrocolloid dressings
• Dressings containing silver or alginates
• Foam dressings

Antibiotics

Wounds are even less likely to heal well if they are infected with bacteria. Depending on how severe the infection is, antibiotics may be considered. They can either be applied to the wound using an ointment or placed on the wound using a compress. Initial study results show that wounds in people with diabetic foot syndrome heal faster as a result. It’s not yet clear whether this also applies to wounds caused by other underlying diseases.

Below are some antibiotics used topically

• Neomycin
• Framycetine

MULTIPLE CHOICE QUESTIONS [ MCQs] :-

1.] Which of the following is absolutely essential for wound healing ?

a. Vitamin D

b. Carbohydrates

c. Vitamin C

d. Balanced diet

2.] Wound contraction is mediated by ?

a. Epithelial tissue

b. Myofibroblast

c. Collagen

d. Elastin

3.] First sign of wound healing is ?

a. Epithelialalization

b. Dilation of capillaries

c. Leukocytic infiltration

d. Localized edema

4.] Maximum collagen in wound healing is seen at which stage of healing ?

a. End of 1 week

b. End of 2 week

c. End of 3 week

d. End of 2 month

5.] During fibroplasia phase, fibroblast migrate into wound after how many hours ?

a. 12 – 24 hours

b. 24 – 48 hours

c. 48 – 72 hours

d. 1 week

6.] The role of collagen is ?

a. Cell adhesion

b. Locomotion

c. Expansion and contraction

d. Strength and support

7.] The most important step in collagen formation in hydroxylation of proline and lysin ?

a. True

b. False

8.] The optimal time to operate on irradiated tissue is ?

a. Between 6 week and 6 months

b. Between 3 weeks and 3 months

c. Between 6 months and 1 year

d. Between 4 weeks and 6 months

9.] Intact dermis contain how much type l collagen and how much type lll ?

a. 50% / 50%

b. 60% / 40%

c. 80% / 20%

d. 25% / 75%

10.] In regeneration ?

a. Granulation tissue

b. Repairing by same type of tissue

c. Repairing by different type of tissue

d. All of the above

SOLUTIONS :-

1.] (c) Vitamin C

2.] (b) Myofibroblast

3.] (b) Dilation of capillaries

4.] (c) End of 3 week

5.] (c) 48 – 72 hours

6.] (d) Strength and support

7.] (a)

8.] (b) Between 3 week and 3 months

9.] (c) 80% / 20%

10.] (b) Repairing by same type of tissue

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REFERENCES :-

1.] Textbook Of Pathology By Harsh Mohan; 7th edition; Page no. 158 – 163.

2.] Robbin’s Basic Pathology; 5th edition; Page no. 85 – 89.

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