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General Pathology > 3-Repair > Flashcards

3-Repair Flashcards

1
Q

Regeneration

A

replacement of injured cells by cells of same type

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2
Q

Healing

A

tissue response to a wound (usually of skin), an inflammatory process in an internal organ, or to cell necrosis in an organ incapable of regeneration; involves two processes

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3
Q

two processes of healing

A
  • regeneration

- scar formation (laying down of fibrous tissue

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4
Q

Cell proliferation is regulated by

A
  • growth factors intrinsic to the microenvironment
  • cell injury
  • cell death
  • mechanical stress (bone)
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5
Q

The most important regulator of cell growth and differentiation (healing) is:

A

prodding resting cells (G zero) to enter the cell cycle

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6
Q

Stable cells:

A
  • quiescent cells
  • usually G0 and low rate of division
  • driven into G1 and rapid proliferation
  • liver, kidney, pancreas, endothelium, fibroblasts
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7
Q

Labile cells

A
  • always dividing
  • replace dying cells
  • epithelial cells of the skin, oral cavity, exocrine ducts, and GI tract; endometrium and bone marrow cells
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8
Q

Permanent cells

A
  • non-dividing cells
  • permanently removed from cell cycle
  • irreversible injury leads only to SCAR
  • nerve cells, myocardium, skeletal muscle
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9
Q

Stem cells

A

-prolonged self-renewal capacity and asymmetric replication (one cell retains its self-renewing capacity and the other enters a differentiation pathway)

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10
Q

Embryonic stem cells (ESC)

A
  • used to study differentiation signals
  • make possible production of knockout mice (inactivate or delete a specific gene in an ESC and inject the ESC into a blastocyst)
  • have potential for repopulation of damaged organs
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11
Q

Adult stem cells (ASC)

A

more restricted differentiation capacity than ESC

  • ASC exist in bone marrow and perhaps other tissues as well
  • ASC are found in niches
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12
Q

Hematopoietic stem cells (HSC)

A

-give rise to all lineages of blood cells and possibly neurons and hepatocytes.

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13
Q

Where are stem cells found in the liver?

A

the canals of Hering
-these give rise to progenitor cells capable of differentiation into hepatocytes or biliary cells when liver injury is severe

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14
Q

satellite cells

A
  • found in skeletal muscle, beneath the myocyte basal lamina
  • they can differentiate into myocytes after injury
  • sometimes they can also become osteogenic and adipogenic
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15
Q

Two major effects of Growth factors

A
  • transcription of genes that were silent in resting cells

- regulate cell entry into and passage through the cell cycle

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16
Q

Four pathways of extracellular signaling

A
  • Autocrine: the mediator acts on the cell that secretes it
  • Paracrine
  • Endocrine
  • synaptic
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17
Q

Autocrine:

A

the mediator acts on the cell that secretes it

  • cytokines on immune cells
  • growth factors on epithelial cells
18
Q

paracrine;

A

mediatory affects cells in the immediate vicinity

  • inflammatory cells in infection sites
  • wound healing process
19
Q

endocrine signaling

A 
regulatory substance (hormone) is released into the blood stream
-ex insulin from islets of langerhans
20
Q

angiogenesis

A

growth of new blood vessels

  • derived from endothelial cell precursors (angioblasts) OR
  • by budding from pre-existing vessels
  • basement membrane degrades
  • endothelial cells migrate, proliferate, and mature
21
Q

In tissues capable of regeneration, ______ is required. If this is absent, healing by scar occurs

A

an intact connective tissue scaffold

22
Q

proliferation requires summoning ____ cells into the cell cycle (primary) and _____ (secondary importance)

A
  • resting or quiescent cells (G zero)

- shortening the cell cycle

23
Q

PGF

A

polypeptide growth factors

24
Q

proteoglycans and hyaluronan

A

growth factor reservoir

-binding water to ECM

25
Q

***granulation tissue

A

pink, soft, granular grossly

26
Q

Scar formation involves the loss of what two things?

A

parenchyma and ECM

27
Q

fibrosis

A
  • (fibroplasia)
  • occurs within the granulation tissue framework (new blood vessels and loose ECM)
  • proliferation of fibroblasts at site of injury
  • deposition of ECM
28
Q

What growth factors are associated with proliferation of fibroblasts at the site of injury?

A

TGF-beta, PDGF, EGF, FGF

-cytokines also help: IL-1, TNF-alpha

29
Q

scar remodeling

A
  • strengthens the tissue
  • METALLOPROTEINASES
  • produced by macrophages, neutrophils, fibroblasts as inactive precursors, in response to local factors
  • debris carried away by phagocytes (debridement)
30
Q

**What are the phases of cutaneous wound healing?

A
  • inflammation
  • proliferation
  • maturation
31
Q

what is the simplest type of healing

A

-primary union (with apposed or sutured tissue edges)

32
Q

secondary union (or intention)

A 
larger defect (than primary)
-tissue edges do not appose each other
33
Q

***what is the sequence of events in wound healing?

A
  • formation of blood clot
  • formation of granulation tissue
  • cell proliferation and collagen deposition
  • scar formation
  • wound contraction
  • connective tissue remodeling
  • recovery of tensile strength
34
Q

formation of the blood clot is done by what cells in what time frame?

A

neutrophils within 24 hours

35
Q

the formation of granulation tissue is more prominent in which type of union, primary or secondary?

A

secondary

36
Q

cell proliferation and collagen deposition is done by what cells in what time frame?

A
  • macrophages replace neutrophil by 96 hours (metalloproteinases, from macrophages)
  • they then clear debris, fibrin,… and promote angiogenesis and ECM deposition
37
Q

To form a scar, granulation tissue is converted to pale, avascular tissue, when is the scar completely acellular and without inflammation?

A

by about 30 days

38
Q

wound contraction occurs within what type of wounds and are done by what type of cells?

A
  • prominent in large surface wounds (secondary union)

- myofibroblasts, which resemble smooth muscle cells, are responsible for contraction and they also lay down ECM

39
Q

which enzymes are responsible for connective tissue remodeling?

A

-Matrix metalloproteinases (MMP)

40
Q

once a wound is healed, what % of its original tensile strength is present?

A

70%, by the third month

41
Q

If inadequate formation of granulation tissue or scar formation occurs:

A
  • wound dehiscence

- ulceration

42
Q

What are the different types of excessive scar formation/wound healing?

A
  • hypertrophic scar/keloid
  • exuberant granulation tissue-“proud flesh”, blocks re-epithelialization and looks like ground beef
  • exuberant proliferation of fibroblasts (fibromatosis)
  • wound contracture

General Pathology (9 decks)

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