What Is Wound Repair?

Wound repair: Wound is the damage caused by normal skin (tissue) to external injury factors such as surgery, external force, heat, current, chemicals, low temperature, and internal factors such as local blood supply disorders. It is often accompanied by the destruction of skin integrity and the loss of a certain amount of normal tissue, and at the same time, the normal function of the skin is impaired. Also called a wound or wound. Wound repair is both wound repair.

Wound repair

According to the healing cycle of the wound, it can be divided into acute wound and chronic wound.

The skin, including its ancillary structures such as hair, nails, sebaceous glands, and sweat glands, is the largest organ of the human body. In adults, on average, the skin area of the whole body is about 7,600 square centimeters, accounting for 15% of the total body weight, and about 1/3 of circulating blood is supplied to the skin (Van De Graaff, 1986). Skin thickness varies from body to body, from the thinnest 0.04mm (eyelid) to the thickest 1.6mm (hand and foot). The skin is the first barrier between the body and nature. Its main function is to protect it from the invasion of environmentally pathogenic microorganisms and the loss of its body fluids. At the same time, the skin also has the functions of feeling, exchanging, and regulating body temperature. However, we can also understand the individual's health, mental state, age, ethnicity, and cultural background through the skin. Therefore, it can be said that the skin is a very important organ of the body. On the tissue structure, the skin can be divided into three layers from the outside to the inside, namely the epidermis layer (Epidermis), dermis layer (Dermis), and subcutaneous tissue (Hypodermis).

I Epidermis The epidermis is the outermost layer of the skin, with a thickness of about 0.04mm. It does not contain blood vessels, and its nutrition is provided by the cells of the basal layer. The outermost layer of the epidermis is the stratum corneum. This layer is an important guarantee for the skin to play a protective function. Moreover, the cells in this layer will continue to fall off. At the same time, the cells of the basal layer will continue to divide and proliferate, moving towards the stratum corneum, supplementing the shed cells. This process normally takes about 28 days. This time is called the turnover time. This time often changes under the influence of skin pathological conditions or external factors, leading to skin diseases, such as skin rubber-like lesions. Epithelium

Wound healing refers to a series of pathophysiological processes in which local tissues are repaired through regeneration, repair, and reconstruction after tissue loss due to the effects of trauma factors. In essence, the body is an inherently defensive adaptive response to tissue and cell damage caused by various harmful factors. This kind of regenerative repair is manifested in the restoration of the lost tissue structure, and can also restore its function to varying degrees.

However, the repair of lost tissue cells can be the "complete recovery" of the original tissue cells-called "Regeneration"; it can also be replaced by non-specific connective tissue proliferation Tissue cells form "incomplete recovery"-called "repair", but the two different results are the same. Basic knowledge of wound healing Regeneration is compensation for the loss of tissues and cells, and is therefore the initiation and foundation of wound healing. Under normal circumstances, some tissues and cells will be continuously consumed, aged and died, and will be continuously supplemented by the same cell division and proliferation, which is called physiological regeneration, such as epidermal shedding and regeneration, and blood cells Periodic apoptosis and supplementation. Its characteristic is that the regenerated cells completely maintain the original structure and function, so it is called Complete regeneration (Complete regeneration). The regeneration after the loss of tissue cells caused by injury is called pathological regeneration or repair regeneration.

When the wound is superficial and the tissue cells are slightly lost, it can be supplemented by the same type of tissue cell division and proliferation, so that it has the same structure and function, forming a complete pathological regeneration. Degree burns, etc. However, when there are many missing tissue cells, the body is often repaired by another alternative tissue, connective tissue, to lose the structure and function of the original tissue and form incomplete pathological regeneration. Clinically the overwhelming majority is this type of regeneration. Wound healing process The basis of wound healing is a series of biological activities such as inflammatory cells such as macrophages, neutrophils, and repair cells such as fibroblasts and epidermal cells. At the same time, the cell matrix is also involved.

Wound healing process one

Coagulation stage

From the moment the wound is formed, the body's first response is its own hemostatic process. This process includes some very complicated biological reactions: v First, the reactive contraction of small blood vessels and capillaries around the wound reduces the local blood flow, that is, the exposed collagen fibers attract platelets to form blood clots; v Later platelets release vasoactive substances such as serotonin and prostaglandins, which further shrink the blood vessels and slow blood flow. At the same time, the released phospholipids and ADP will attract more platelets to aggregate. v Finally, endogenous and exogenous coagulation processes will also be initiated. After the coagulation process is over, the body begins to heal the wound.

Wound repair and healing process (2)

Inflammation phase

This period is 2-3 days before the formation of homemade noodles. Due to the contraction of local blood vessels, ischemia is caused by local tissues, causing the release of histamine and other vasoactive substances, so that the local blood vessels in the wound are dilated; at the same time, the body is caused by the presence of necrotic tissue and possible pathogenic microorganisms. Defensive response (inflammatory response): immune cells such as granulocytes and macrophages move and concentrate towards the wound.

On the one hand, granulocytes prevent or engulf invading bacteria. On the other hand, macrophages engulf the digested and necrotic tissue fragments. At the same time, the autolysin released by the destruction of tissue cells can also digest and dissolve the necrotic tissue fragments. Clean the wound to start the tissue repair process. In addition to phagocytosis of digestive tissue cell debris, macrophages are also a key factor in stimulating the proliferation and differentiation of fibroblasts and the synthesis of collagen. This process is also called the Debridement phase. At the same time, the wound shrinks reactively to reduce the area of the wound. Clinically, because the wounds in this period are mostly covered by black necrotic tissue, it is also called the black period. When this layer of necrotic tissue is removed, the wound surface will still be covered by a thin layer of decayed inactivated tissue, making the wound look yellow. Therefore, the clinical stage is often referred to as the yellow stage at this time.

Wound healing process III

Reconstruction phase

This period can be divided into 2 stages: Epithelialisation and Granulation. Also known as Proliferation. This period is about 2-24 days after the wound is formed. v Epithelial cell regeneration Wound repair First, the basal cells that survived around the wound began to proliferate and shifted towards the center. At the same time, proliferation of basal cells stimulates reactive hyperplasia of capillaries and connective tissue at the base of the wound. When the wound surface is covered with newly-born epithelial cells, the appearance of the wound surface is pink, so it is also called the pink phase at this time. v Granulation tissue formation Subsequently, the proliferation of basal cells stimulates the growth of granulation tissue. At the same time, growth factors released by macrophages such as platelet-derived growth factor (PDGF), -transformation growth factor (-TGF), and -transformation growth factor (-TGF) accelerate the formation of granulation tissue. The formation of granulation tissue has important biological significance, mainly manifested in:

(1) Fill the defect of the organization

(2) Protect wounds, prevent bacterial infections, and reduce bleeding

(3) Mechanized blood clots and necrotic tissue and other foreign bodies are bright red due to the appearance of new and healthy granulation tissue. Therefore, the wound at this time is clinically referred to as the red phase. With the continuous formation of flesh and tooth tissue, the absence of wound tissue is filled, and the epithelial cells migrate from the periphery of the wound to the center, so that the wound can be completely covered by the regenerated epithelial cells.

The maturation phase of the wound healing process. However, after the wound is completely covered by regenerated epithelial cells, the wound healing process does not completely end. This is the maturity period of the wound. Because the new granulation tissue and epithelial cells need to further divide, differentiate, and transform to strengthen their strength, they can finally heal the wound. This process is mainly manifested in the following two aspects:

(1) The newly formed epithelial cells continue to divide and thicken the epidermal layer

(2) Internal transformation of granulation tissue: the arrangement of the formed collagen fibers changes, which increases the strength of the new connective tissue; at the same time, the number of capillaries decreases, causing the local color of the wound to decrease, close to normal.

This process takes a long time, often more than one year. Before the wound healing is completed and mature, the wound is still easy to be damaged again. Because the wound has been completely healed on the surface, this period is often ignored by patients and medical staff. This is why clinically, chronic wounds often occur at the same site.