AP - Healing and repair

[blank_start]Healing[blank_end] is the body's replacement of destroyed tissue by [blank_start]living[blank_end] tissue

Repair can occur in three ways: [blank_start]Resolution[blank_end], [blank_start]Regeneration[blank_end] and Organisation.

Resolution only occurs if tissue sustained [blank_start]minimal[blank_end] damage - inflammatory reactions [blank_start]occur[blank_end] -> tissue is [blank_start]restored[blank_end] to former function and structure

Regeneration are usually in tissues where cells have [blank_start]mitotic[blank_end] ability. [blank_start]Labile[blank_end] cells are ones that continue to [blank_start]multiply[blank_end] in order to [blank_start]replace[blank_end] lost cells, whilst [blank_start]stable[blank_end] cells cease to multiply when growth of mature organ is reached.

Organisation is where damage is [blank_start]severe[blank_end] and [blank_start]cell loss[blank_end] is great. Inflammatory response [blank_start]subsides[blank_end], [blank_start]damage[blank_end] is so great, [blank_start]granulation tissue[blank_end] forms and matures to form a [blank_start]scar[blank_end]. Especially in tissues composed of permanent cells with no [blank_start]mitotic ability[blank_end] such as [blank_start]neurons[blank_end].

[blank_start]Regeneration[blank_end] and [blank_start]hyperplasia[blank_end] both show cell division. These are both kept under control compared to neoplasia. [blank_start]Regeneration[blank_end] is the replacement of lost cells, not more cells. [blank_start]Hyperplasia[blank_end] is the excessive multiplication of cells which results in larger amount of tissue than normal.

There are 2 ways a skin wound will heal - [blank_start]First intension[blank_end]: Clean, precise [blank_start]lesion[blank_end] and also the Second intension: There is [blank_start]tissue loss[blank_end]

Healing by first intension - There is [blank_start]no infection[blank_end], and edges of wound are held [blank_start]together[blank_end] by sutures or butterfly tape.

All of the below are first intension healing 1 except

In first intension healing 2, [blank_start]epithelium[blank_end] begins to grow in from the edges and comes together within 2 days, and formation of epithelial spur. Epithelial growth stimulates a minimal amount of [blank_start]granulation tissue[blank_end] from surrounding connective tissue. Fibroblasts start to lay down [blank_start]collagen[blank_end], and wound edges [blank_start]unite[blank_end].

First intension healing 3 includes

In healing by second intension, the [blank_start]wound[blank_end] gapes and there is [blank_start]loss[blank_end] of tissue due to infection. First stage is that there's an [blank_start]open[blank_end] and excised wound, [blank_start]bleeding[blank_end] into wound and there are blood clots. Next stage is the [blank_start]growth[blank_end] of new epithelium in from sides and through the clot, and eventually meets in centre. [blank_start]Granulation[blank_end] tissue grows in from adjacent CT and base of wound. [blank_start]Fibroblasts[blank_end] and endothelium

Last stage of second intension healing includes wound [blank_start]contraction[blank_end], action of transformed [blank_start]fibroblasts[blank_end], they contrast and [blank_start]collagen[blank_end] is laid down. This in turn [blank_start]reduces[blank_end] wound size. There is also a [blank_start]decrease[blank_end] in vascularity and [blank_start]more collagen[blank_end] is laid down --> [blank_start]fibrous scar[blank_end] formed.

What occurs after wounding 1?

In after wounding 2, there is [blank_start]hyperplasia[blank_end], and [blank_start]loss[blank_end] of normal cell adherence. There's [blank_start]flattening[blank_end] of rete ridges, and cells slide over each other.

In granulation tissue 1, there is [blank_start]proliferation[blank_end] of CT elements, wound is [blank_start]filled[blank_end] and lost tissues are replaced by fibroblasts, venular [blank_start]angioblasts[blank_end] multiply and bud off, whilst [blank_start]macrophage[blank_end] and platelet degradation products are [blank_start]chemotactic[blank_end] for more inflammatory cells.

Granulation tissue 2 consist of from day 3 appearance of capillary buds and [blank_start]sprouts[blank_end]. They then [blank_start]anastomose[blank_end] with others to flow, start to differentiate into arterioles and venules. Granulation 3 [blank_start]produce[blank_end] types 1 and 3 collagen. Early wound healing first makes [blank_start]hyaluronic[blank_end] acid and sulphated proteoglycans. Granulation tissue 4 consist of total amount of [blank_start]collagen[blank_end] laid down by 3 weeks, and tensile strength of scar tissue increasing by the replacement of type 3 to type 1 collagen. There's a further [blank_start]decrease[blank_end] in vascularity.

Cicatrization is the later [blank_start]reduction[blank_end] in size of the scar

Skin would consist of