Pathology: Principles Of Wound Healing/tissue Repair

Front 1

Which cells are continuously regenerated through life to replace other cells that are lost through normal physiological processes?

Back 1

Labile cells

(all epithelial surfaces, ducts, lymphoid and hematopoietic tissue, etc)

Front 2

What type of cells cannot regenerate?

Back 2

Permanent cells
(striated cells
cardiac muscle cells
neurons-- axons can be regenerated in the PNS as long as cell body is not damaged, but neurons in the CNS cannot be repaired at all)

Front 3

Cells which retain ability to regenerate but do not do so under normal circumstances

Back 3

Stable cells

(hepatocytes, renal tubular epithelial cells, glandular parenchymal cells, endothelial cells, mesenchymal cells, etc).

These cells are in the Go phase of the cell cycle until they are stimulated to enter the G1 phase

Front 4

What type of cells are hepatocytes, renal tubular epithelial cells, glandular parenchymal cells, endothelial cells, mesenchymal cells...?

Back 4

Stable cells

Front 5

What are progression factors?

Back 5

Growth factors that promote DNA replication

Front 6

What are competence factors?

Back 6

Growth factors that "prime" the cell for DNA replication.

Front 7

When cells of some tissues sense that the density of cells has fallen below a certain level, they are stimulated to ________.

Back 7

Divide

Front 8

Describe 3 hypotheses that explain how a cell is stimulated to reenter the G1 phase of the cell cycle and proliferate?

Back 8

1. Stimulation by growth factors
2. Loss of contact inhibition
3. Decrease in cellular density

Front 9

What cells are generally involved in the production of collagen to produce a scar?

Back 9

Fibroblasts

Front 10

What is a cicatrix?

Back 10

A scar

Front 11

Collagen Types I, II, and III are ______ in structure and found in _____ spaces.

Back 11

Fibrillar.
Interstitial

Front 12

What is the predominant collagen type found in skin, bone, and most organs?

Back 12

Type I

Front 13

Which collagen types are found in basement membranes?

Back 13

Non-fibrillar (amorphous) types
(especially Type IV)

Front 14

What is the soluble form of collagen called (before it is excreted from the cell?)

Back 14

Procollagen

Front 15

Before excretion from the cell, procollagen is modifed utilizing ________ as a cofactor

Back 15

Vitamin C

Front 16

This process involves very little loss of tissue substance and a minimal amount of inflammatory exudate and necrotic debris.

Back 16

"primary union"

Front 17

How are macrophages and fibroblasts localized to the wound site?

Back 17

Chemotaxis. Chemokines are attached to fibronectins that coat fibrin stands (formed from the inflammatory exudate)

Front 18

Once re-epithelialization is complete, the cells cease proliferation. Why?

Back 18

Growth inhibitors:
- TGF-B
- a-interferon
- Prostaglandin E2
- Heparin

Front 19

During wound healing, what happens within the first 24 hours?

Back 19

Clot formation and inflammation have already occured. Also, epithelial cells from the wound margins begin to proliferate and migrate toward the midline

Front 20

What is present after 48 hours of wound healing?

Back 20

A single layered epithelium covers the surface of the wound.

Front 21

What happens by the 2nd day of wound healing?

Back 21

The fibroblasts from the healthy wound margins are "activated" (increased cell size due to increase in the rough endoplasmic reticulum)

Front 22

What do fibroblasts secrete?

Back 22

Collagen and elastic fibers.
Other matrix components (fibronectins, hyaluronic acid, glycosaminoglycans, proteoglycans, glycoproteins)

Front 23

Around the 3rd day of wound healing, what happens?

Back 23

Neovascularization begins

Macrophages begin to replace the neutrophils.
They clean up cell debris along the wound margins and secrete factors which act in concert w/ the fibronectins to promote angiogenesis and neovascularization of the wound.

Front 24

During neovascularization, how do macrophages and fibroblasts get their nutrients?

Back 24

Endothelial cells proliferate and develop a lumen, but are "leaky" and allow protein and fluid to escape into the surrounding tissue--

This enhances the inflammatory edema AND supplies nutrients

Front 25

What is "granulation tissue?"

Back 25

Combination of neovascularity, "activated" fibroblasts and mixed inflammatory infiltrate (mostly macrophages) embedded in an edematous ground substance.

Front 26

What is usually present by the 5th day of tissue repair?

Back 26

Granulation tissue

Front 27

Are scars cellular or acellular?
Vascular or avascular?

Back 27

Acellular (fibroblasts undergo apoptosis)
Avascular

Front 28

What is the major protein involved in scar formation?

Back 28

Collagen

Front 29

What are the 6 steps of healing by first intention?

Back 29

1. Clot formation
2. Inflammation
3. Epithelial regeneration
4. fibroblast activation
5. Neovascularization
6. Scar formation

Front 30

What happens after neovascularization during wound healing (1st intention)?

Back 30

Scar formation

Front 31

What happens after fibroblast activation during wound healing? (1st intention)

Back 31

Neovascularization

Front 32

What happens after epithelial regeneration during wound healing?

Back 32

Fibroblast activation

Front 33

What happens after clot formation during wound healing?

Back 33

Inflammation

Front 34

This refers to the repair process involved when there is sufficient loss of tissue to prevent coaptation of the wound margins (abscesses, ulcers, infarctions, etc)

Back 34

"Second union"--healing by second intention

Front 35

What kind of wound healing is necessary for extensive inflammatory exudate and necrotic debris?

Back 35

Secondary union

Front 36

Why are wounds that require "healing by second intention" more prone to infections?

Back 36

Migration of surface epithelium progresses slowly--it can only grow as far as the underlying granulation tissue which grows at a very slow rate

Front 37

Wound contraction is a phenomenon that occurs during what type of wound healing?

Back 37

Secondary union.

Front 38

What type of cells are responsible for wound contraction?

Back 38

Myofibroblasts

Front 39

Why can wound contraction sometimes be deleterious?

Back 39

It may lead to disfiguring scars or "frozen" joints.

Front 40

What type of collagen predominates early in wound healing?

As the scar matures, then what type of collagen predominates?

Back 40

Type III

Type I

Front 41

Is a scar as strong as the original tissue?

Back 41

NO.

Front 42

This refers to the excessive buildup of granulation tissue which protrudes above the surface of the wound and prevents re-epithelialization

Back 42

Exuberant granulation

"Proud flesh"

Front 43

This refers to a build up of excessive amounts of collagen leading to disfiguring scars

Back 43

Keloid formation

Front 44

What does tensile strength depend on?

Back 44

The type and the amount of collagen deposited.