lecture 3/tutorial 1 - healing

Question 1

What is regeneration in terms of tissue repair?

Answer 1

The regrowth of cells of the same type that were lost in the necrosis.

Question 2

What is replacement in tissue repair?

Answer 2

The replacement of some of the necrosis damaged tissue with connective tissue - fibrosis/scarring

Question 3

In tissue repair, what is the outcome of the replacement phase?

Answer 3

Fibrosis/scarring as connective tissue is laid down.

Question 4

What are stable cells?

Answer 4

Cells that will only divide when given a specific stimulus

Question 5

What are labile cells?

Answer 5

Cells that are constantly dividing to regenerate tissue

Question 6

What are permanent cells?

Answer 6

Cells that cannot divide to regenerate tissue.

Question 7

What are the 3 types of cell, in terms of their proliferative potential/tendency to divide?

Answer 7

Stable cells, permanent cells, labile cells.

Question 8

What is fibrosis/scar tissue formation in terms of tissue repair?

Answer 8

The replacement of non-regenerated cells with connective tissue

Question 9

What is lost in scar tissue formation/fibrosis?

Answer 9

Parenchyma (functional tissue) and extracellular matrix (ECM)

Question 10

What is parenchyma?

Answer 10

The essential, functional elements of an organ, distinct from the connective and supporting tissues.

Question 11

What are the 4 stages of tissue repair by scarring?

Answer 11

1.) blood vessel formation - angiogenesis
2.) fibroblast migration and proliferation
3.) deposition of ECM
4.) maturation and remodelling of fibrous tissue

Question 12

What tissue type is formed in healing, and ultimately results in fibrosis?

Answer 12

granulation tissue

Question 13

What are the components of granulation tissue?

Answer 13

blood vessels, fibroblasts, ECM, inflammatory cells (macrophages, neutrophils,etc.)

Question 14

What is angiogenesis?

Answer 14

Formation of new blood vessels.

Question 15

How does angiogenesis occur in granulation tissue formation?

Answer 15

EPCs (endothelial progenitor cells) migrate from the bone marrow to the site of blood vessel network formation.

Question 16

What cell type makes the ECM that results in fibrosis?

Answer 16

Fibroblasts

Question 17

What ECM component is particularly abundant in fibrosis?

Answer 17

Collagen for strength

Question 18

How does scar remodelling occur?

Answer 18

Metalloproteinases turnover interstitial proteins.

Question 19

What factors influence the success of healing/tissue repair?

Answer 19

nutrition, metabolic status, steroids, infection, movement, blood supply

Question 20

What are the 2 types of skin wound healing and unification?

Answer 20

Primary union/intention, secondary union/intention

Question 21

What is the tensile strength of a healed scar?

Answer 21

~80%

Question 22

What is the process of healing by primary intention?

Answer 22

coagulation and clot formation, inflammatory reaction by neutrophils, basal epithelial cells grow along wound edges, neutrophils replaced my macrophages (by day 3), granulation tissue forms, fibrous scar forms under the intact epidermis

Question 23

What is the process of healing by secondary intention?

Answer 23

Coagulation and large clot forms, extensive inflammaotry reaction with neutrophils due to necrosis, basal epithelial cells grow at edges along with myofibroblasts, macrophages replace neutrophils, granulation tissue grows, replaced by large fibrous scar

Question 24

What type of cell grow in secondary intention and act to contract to minimise wound gap?

Answer 24

Myofibroblasts

Question 25

What are the 3 phases of fracture healing?

Answer 25

Inflammatory phase, reparative phase, remodelling phase

Question 26

What happens during the inflammatory phase of fracture healing?

Answer 26

Haemorrhage and clot formation due to tearing of periosteum and adjacent soft tissues, necrosis of bone fragments, acute inflammatory response with fluid and exudate. Granulation tissue begins to grow by 2-5 days.

Question 27

What happens during the reparative phase of fracture healing?

Answer 27

Osteoblasts grow from stem cells in granulation tissue and synthesise ECM, cartilage appears in the granulation tissue forming a callus, and is slowly replaced by bone

Question 28

What clears the clot and bone fragments in bone healing?

Answer 28

Phagocytes via phagocytosis

Question 29

What cells are involved in the building and reorganisation of the callus in the remodelling phase of bone healing?

Answer 29

osteoclasts and osteoblasts

Question 30

What chemical mediator is responsible for the formation of granulation tissue?

Answer 30

VEGF - vascular endothelial growth factor