10. tissue repair

Question 1

tissue turnover

Answer 1

maintaining tissue architecture and function during progressive aging and constant changes in demand

Question 2

tissue repair

Answer 2

restoration of tissue architecture and function after damage

repair repeats morphogenesis

Question 3

what happens up to 28th week of of embryo

Answer 3

no scarring and inflammation during repair

Question 4

the key process in adult tissue turnover and repair

Answer 4

inflammation

it is a homeostatic process

tissue maintenance and immune defence are part of the same process

Question 5

stem cell niche

Answer 5

microenvironment of a stem cell a spatial structure in which stem cells are housed and maintained allowing self-renewal in the absence of differentiation

Question 6

what does stem cell division give rise to

Answer 6

transit amplifying cells

= daughter cells comitted to differentiation

undergo clonal expansion

one stem cell becomes dormant after division

Question 7

what is the fate of cells regulated by

what are the different types of these

Answer 7

external signals- cross talk with other cells and ECM (microenvironment)

juxtacrine signalling- between tissues

paracrine signalling- exchange signals

endocrine signalling- blood

Question 8

what is the factor that determines cell differentiation

Answer 8

the plane of cell division

Question 9

what controls the differentiation of epidermis

Answer 9

The fate of the daughter cells is controlled

interactions with the basement membrane

signals from neighbouringcells

• Activation of the Wnt pathway inhibits the switch from stem cell to TA cell
• Notch signaling in a stem cell inhibits adjacent cells from staying stem cells.

Question 10

Answer 10

Question 11

classification of cell death

Answer 11

morphological appearance (apoptotic, necrotic, autophagicor mitosis-associated)

enzymological criteria (w/ and w/o the involvement of nucleases or proteases, such as caspases, calpains, cathepsinsand transglutaminases)

functional aspects (programmed vs. accidental, physiological vs. pathological)

immunological characteristics (immunogenic vs. non-immunogenic).

Question 12

which protein is involved in recognition of cells that are damaged beyond repair?

Answer 12

phosphatidylserine- direct binding of phagocyte with apoptotic cell

indirect binding via bridging proteins

Question 13

three groups of tissues

Answer 13

Liable: bone marrow, skin, GI epithelium)

• continuously renewing
• can easily regenerate after injury

Stable: (e.g. liver, kidney, pancreas)

• conditionally renewing
• limited ability to regenerate (except liver!)
• normally in G0, but can proliferate if injured

Permanent:

(e. g. neurons, cardiac muscle)
- static or non-proliferative
- cannot regenerate

(injury always leads to scar)

Question 14

what type of stem cells are adult stem cells

Answer 14

mostly multipotent, some pluripotent

Question 15

two ways of tissue repair

what are the phases

Answer 15

regeneration

replacement: tissue replaced by scar= non functioning connective tissue

can be both

Inflammation hours –days

Restricting damage

• Debridement
• Antimicrobial defence

Proliferation days –weeks

Producing replacement

• Specific cells
• Specific matrix

Maturation weeks –months/years

Restoring function

•Functional remodeling

Question 16

regeneration in bones, liver, NS, and skin

Answer 16

Bone full regenerative capacity for all tissues involved

Liver tissue dependent parenchyma regenerates if mesenchyme intact, if not scarring

ECM must still be intact

Nervous system

PNS: regeneration possible (proximal grows back to repair distal)

CNS:always scarring, leads to astrogliosis

Skin layer dependent epidermis = regeneration

dermis & hypodermis= scarring

Question 17

wound healing in epidermis and dermis

Answer 17

epidermis:

• adjacent keratinocytes“leap-frog” along collagen fibresuntil they meet
• if gap is too wide, they stop
• when they meet, they form a sheet and cover the denuded area

dermis:

• Endothelial cells follow laminin fibresuntil they meet and fuse
• if gap is too wide, the capillary sprouts turn sideways
• critical wound size about 2-3cm

Question 18

first intention wound healing

Answer 18

small wounds

narrow margins

regeneration >> fibrosis

healing is fast;

minimal scarring

Question 19

second intention wound healing

Answer 19

larger wounds

wide margins

fibrosis >> regeneration

healing is slower;

more scarring

inevitable infection

Large burns and ulcers

Question 20

wound closure

Answer 20

aim to initiate 1st intention healing

suture removal depends on location

stitch, staple, glue, tape

Question 21

wound management

wound covers

Answer 21

must be clean

larvae therapy

skin mesh, enginereed epidermal sheets and skin substitutes to cover large or non healing wounds

Question 22

wound remodelling

Answer 22