Tissue Injury & Repair Flashcards
Can the number of heart cells increase (hyperplasia)?
No - the heart has a fixed number of cells
What is healing the response of?
1) Wound
2) Inflammatory process
3) Cell necrosis
What 2 processes are involved in healing?
1) Regeneration (restore normal tissue)
2) Repair (tissue can regain its normal function)
Which organ is unable to regenerate?
Heart - it heals by fibrosis, leading to scar tissue
Definition of regeneration:
The growth of cells and tissues to replace lost structures, with the aim to restore normal tissue
What are the 2 requirements for regeneration to take place?
1) A tissue that has proliferative capacity
2) Extracellular matrix and proteins
Which organ has a high proliferative capacity?
Liver
Definition of repair:
A combination of regeneration and scar formation in order to restore the normal function of the tissue
At what level of the skin does regeneration take place?
Epithelium
At what level of the skin does scar formation take place?
Subcultaneous
What depends on which type of healing takes place?
The degree of injury
Which type of healing process will occur for each of the 2 types of inflammation?
Acute inflammation -
Superficial skin = regeneration
Subcultaneous = repair
Chronic inflammation - fibrosis
Evaluation of the ability for regeneration to take place in Amphibians:
Good regenerative abilities
Evaluation of the ability for regeneration to take place in mammals:
Only have a few true examples of regernation
Name the examples of true regeneration in mammals:
1) Liver
2) Superficial skin layer
3) Bone fractures
How do mammals compensate for only having a few examples of true regeneration?
Hyperplasia and hypertrophy
When does fibrosis occur and how is the scar formed?
Fibrosis occurs when the degree of injury is serious and chronic inflammation ha occurred.
Scar formation occurs when collagen and extra-cellular matrix components are deposited
Which cells are responsible for depositing the collagen and extra-cellular matrix components ?
Parenchymal cells and fibroblasts
The sequence of healing from day 0-14:
0-3: 1) Injury 2) Inflammation 3) Angiogenesis 4) Migration of parenchymal cells and fibroblasts
0-7: 1) Pro-liferation of parenchymal cells and fibroblasts
9-14: Depends on level of injury/ type of inflammation
If acute:
Superficial - regeneration
Subcultanous - repair
If chronic:
Fibrosis - scar formation
What are the 2 types of wounds?
First Intention and Secondary Intention
What are first intention wounds?
The edges of the wound will be close together and so healing of the wound doesn’t take long
What are secondary intention wounds?
The edges of the wound will be far apart and so it takes longer for the wound to heal
What is the difference between the healing results of first intention and secondary intention wounds?
First intention: small scab
Secondary intention: large scab with larger amounts of granulation tissue
What occurs in secondary intention to try and bridge the gap between the edges of the wound?
Wound contraction
What are the 2 classes of factors that affect wound healing?
Local factors and systemic factors
Name the 4 local factors that affect wound healing?
1) Size of the wound
2) How well vascularised the tissue is
3) Type of wound - clean or infected
4) Mechanical forces (e.g. scab picking)
Name the 4 systemic factors that affect wound healing?
1) Nutritional status
2) Metabolic status
3) Circulatory status
4) Hormones
Which hormones can prolong healing?
Steriods
What are the 3 complications of wound healing?
1) Deficient scar formation - resulting from open wounds
2) Keloid scar formation - resulting from excessive healing
3) Contractures - resulting from burn wounds
How can wound infections be prevented?
1) Keeping the area clean
2) Regular wound dressings
3) Looking out for signs of injections
Is bleeding at the site of infection normal?
Each area of injury will have a normal degree of bleeding. Anything beyond this normal degree will indicate internal bleeding.
Define pressure/bed sores and where are they normally located?
Unrelieved pressure over an area of the body and they are normally located on boney areas
What causes pressure/bed sores?
1) Lack of blood supply to the area due to the unrelieved pressure
2) Shearing factors that traumatise skin
What results from pressure/bed sores?
1) Ischaemia
2) Cell necrosis
3) Cellulitis
4) Superimposed and deep seated infections
5) Osteomyelitis
