Tissue Renewal And Repair: Regeneration, Healing And Fibrosis

Question 1

Repair of damaged tissues occurs by two types of reactions

Answer 1

Regeneration
Connective tissue deposition

Question 2

Regeneration

Answer 2

Proliferation of uninjured residual cells
Maturation of tissue stem cells
Involves cell proliferation
Driven by growth factors
Dependent on the integrity of the extracellular matrix and by the development of mature cells from stem cells

Question 3

Scar formation

Answer 3

Deposition of connective tissue to form a scar
Injured tissues are incapable of complete restitution

Question 4

Ability of tissues to repair themselves determined by

Answer 4

Their own intrinsic proliferative capacity

Question 5

Which cell types proliferate during tissue repair

Answer 5

Remnants of the injured tissue
Vascular endothelial cells
Fibroblasts

Question 6

Features of the Labile tissues

Answer 6

Continuously dividing tissues
Replaced by maturation from stem cells
Pool of stem cells needs to be preserved for regeneration

Question 7

Where Labile tissues found at

Answer 7

Hematopoietic cells—> Bone marrow
Surface epi—> Skin,Oral cavity, Vagina, cervix
Cuboidal epi of —> ductus draining exocrine organs
Columnar epi of—> GIT,uterus and Fallopian tubes
Transitional epi of—> urinary tract

Question 8

Features of Stable tissues

Answer 8

Not proliferating tissues
Capable of dividing in response to injury or loss of tissue mass
Cells in the G0
Can proliferate in response to growth factors

Question 9

Where are stable tissues found at

Answer 9

Most solid organs= Liver, Kidney,Pancreas
Endo cells
Fibroblasts smooth muscle cells

Question 10

Features of permanent tissues

Answer 10

Consist of terminally differentiated nonproliferative cells
Injury to these is irreversible
Results in scar formation

Question 11

Where are permanent tissues found at

Answer 11

Majority of neurons
Cardiac muscle cells
*skeletal muscle cells

Question 12

Cell proliferation is driven by which signals

Answer 12

Growth factors
From the extracellular matrix

Question 13

Features of the Growth factors

Answer 13

Chemical mediators
Promote cell survival and proliferation
Some act on multiple types
Some act as cell specific
Produced by cells near the site of damage
**most important source is macrophages
Epi and stromatol cells also produces GFs
Paracrine signaling

Question 14

Result of Growth Factors

Answer 14

Expands cell population by stimulating cell division and increase in cell size

Question 15

Importance of ECM-Cell Matrix interactions

Answer 15

Regulates proliferation, movement and differentiation of the cells
Important role in wound healing, chronic fibrotic processes,tumor invasion and metastasis

Question 16

Main components of ECM

Answer 16

Basement membrane
Interstitial matrix

Question 17

Which structure act as a Reservoir for GFs

Answer 17

ECM

Question 18

Cell and tissue regeneration in intestine and skin

Answer 18

Injured cells are rapidly replaced by proliferation of residual cells
Differentiation of cells derived from tissue stem cells

Question 19

Cell and tissue regeneration in Bone Marrow

Answer 19

Driven by GFs called colony-stimulating factors

Question 20

Cell and tissue regeneration in parenchyma organs

Answer 20

Generally limited process
Except LIVER
Kidney removal elicits compensatory response (hypertrophy + hyperplasia) in the contralateral kidney.

Question 21

Regeneration of the liver occurs by two major mechanisms

Answer 21

1-Proliferation of remaining hepatocytes
2- Repopulation from progenitor cells

Question 22

When repair cannot be accomplished by regeneration alone in severe or chronic injury

Answer 22

When the CT framework gets damaged
Nondividing cells are injured

Question 23

Replacement of the non regenerated cells needs to be done by

Answer 23

CT

Question 24

Main steps in repair by scarring

Answer 24

Clot formation
Inflammation
Angiogenesis and formation of granulation tissue
Migration and proliferation of fibroblasts,collagen synthesis
CT remolding

Question 25

What is Angiogenesis

Answer 25

Process of new blood vessel development from existing vessels

Question 26

Molecules that are involved in Angiogensis

Answer 26

Growth factors= VEGFs,FGFs
Notch signaling
ECM proteins
Enzymes= Matrix metalloproteinases

Question 27

**What is the most important cytokine for the synthesis and deposition of CT proteins

Answer 27

TGF-beta

Question 28

**In Granulation tissue which molecule is not prominent

Answer 28

Collagen

Question 29

In tissue remodeling why formation of scar is seen

Answer 29

Scar remodeled to increase its strength and contract it
With time CT will be degraded and the scar will shrink

Question 30

2 classifications of healing of skin wounds

Answer 30

1-First intention (primary union) = epi regeneration with minimal scarring
2-Second intention (secondary union) = larger wounds heal by combination of scarring and regeneration

Question 31

Pathological aspects that effects repair

Answer 31

Infection
Diabetes
Nutritional status
Glucocorticoids
Mechanical factors
Poor perfusion
Foreign bodies
Type and extend of tissue injury
Location of the injury

Question 32

Examples of Chronic Wounds

Answer 32

Venous leg ulcers
Arterial ulcers
Pressure sores
Diabetic ulcers

Question 33

Excessive scarring examples

Answer 33

Hypertrophic scar
Keloid
Wound contracture

Question 34

Examples of Fibrosis in Parenchymal organs

Answer 34

Scleroderma
Idiopathic pulmonary fibrosis
Liver cirrhosis
End stage kidney disease
Constrictive pericarditis