Cellular Repair

Question 1

What cell type plays a central role in repair?

Answer 1

Activated M2 type macrophages

Clear agents, provide growth factors, stimulate fibroblast proliferation

Question 2

What is regeneration?

Answer 2

Proliferation of cells that survive the injury and retain the capacity to proliferate

Tissue stem cells may also contribute to this process

Question 3

How does a tissue repair itself if regeneration is not possible?

Answer 3

Connective tissue deposition

Question 4

What is fibrosis?

Answer 4

Extensive deposition of collagen that occurs in the lungs, liver, kidney, and other organs as a consequence of chronic inflammation

Can be responsible for organ dysfunction and failure

Question 5

What is organization?

Answer 5

Fibrosis develops in a tissue space occupied by an inflammatory exudate

E.g. organizing pneumonia

Question 6

What are labile tissues?

Answer 6

Cells of these tissues are continuously being lost and replaced by maturation from tissue stem cells and proliferation of mature cells

Most surface epithelia, cuboidal epthilia of exocrine organs

Question 7

What are stable tissues?

Answer 7

Cells of these tissues are quiescent and have only minimal proliferative activity

The parenchyma of most solid tissues, exception is liver

Question 8

What are permanent tissues?

Answer 8

The cells of these tissues are considered to be terminally differentiated and nonproliferative in postnatal life

Brain, Heart, most muscle

Question 9

What are the three components of connective tissue repair (scar formation)?

Answer 9

Angiogenesis

Formation of granulation tissue

Remodeling of connective tissue

Question 10

What is angiogenesis?

Answer 10

Formation of new blood vessels to supply nutrients and oxygen to support the repair process

Question 11

Why are newly formed vessels leaky and what does this contribute to?

Answer 11

Incomplete interendothelial junctions and VEGF increases vascular permeability

Accounts for edema that may persist in healing wounds long after the acute inflammatory response has resolved

Question 12

How does granulation tissue form?

Answer 12

Migration and proliferation of fibroblasts and deposition of loose connective tissue, together with the vessels and interspersed leukocytes

Question 13

What is connective tissue remodeling?

Answer 13

Maturation and reorganization of the connective tissue produce the stable fibrous scar

Question 14

How does infection affect tissue repair?

Answer 14

Prolongs inflammation and potentially increases the local tissue injury

Question 15

How does diabetes affect tissue repair?

Answer 15

Comprises tissue repair through many mechanisms and is one of the most important systemic causes of abnormal wound healing

Question 16

How does nutritional status affect wound repair?

Answer 16

Things like protein deficiency and vitamin C deficiency inhibits collagen synthesis and retards healing

Question 17

How do glucocorticoids affect healing?

Answer 17

May result in weakness of the scar due to inhibition of TGF-B production and diminished fibrosis

May be desirable, e.g. corneal infections to reduced opacity from collagen deposition

Question 18

How does the type and extent of tissue injury affect healing?

Answer 18

Extensive injury will probably result in incomplete tissue regeneration and at least partial loss of function, even in tissues composed of stable and labile cells

Question 19

What is resolution?

Answer 19

Repair of inflammation arising in tissue spaces developing extensive exudates

Occurs by digestion of the exudate by proteolytic enzymes of leukocytes and resorption of the liquified exudate

Question 20

What is healing by first intention?

Answer 20

When injury only involves the epithelial layer

Rapid activation of coagulation

By day 3, neutrophils have been replaced by macrophages and granulation tissue

By day 5 neovascularization reaches its peak as granulation tissue fills the incisional space

Question 21

What is healing by second intention?

Answer 21

Occurs when cell or tissue loss is more extensive

Wound contraction by the action of myofibroblasts

Question 22

What are hypertrophic scars and Keloid similarities?

Answer 22

Accumulation of excessive amounts of collagen

Question 23

What are characteristics specifically of keloids?

Answer 23

Extend beyond site of original injury

Rarely regress and continue to be composed of nodular whorls

Recur

More likely in dark pigmented skin

Question 24

What is Proud Flesh?

Answer 24

Formation of extensive amounts of granulation tissue, which protrudes above the level of the surrounding skin and blocks reepithelialization

Question 25

What are two complications of inadequate granulation?

Answer 25

Wound dehiscence

Ulceration