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Define repair and regeneration
- Repair - restoration of tissue structure and function after an injury
- Regeneration - replacement of normal tissue components and return to a normal state
What circumstances are needed for regeneration?
- Minimal trauma, short term
- Lack of infection
- Good hygiene
- Good circulation
- Lesion position (eg not over a joint)
When does healing result in scar formation?
If the tissues are incapable or complete recitation or if the supporting strutters are severely damaged
Briefly describe the mechanisms regulating cell populations
In any tissue there is a baseline population. This is fed into be stem cells (in the basal layer of the epidermis in skin) all the time just as cells are lost by apoptosis all the time. Some areas will have increased proliferation e.g. in a skin wound the epidermis will be proliferating.
What type of epithelium is the epidermis composed of?
Stratified keratinised squamous epithelium
What are the different layers of skin?
- Epidermis = epithelial cells
- Dermis = underlying connective tissue
- Subcutis = adipose tissue
What are the different layers of the epidermis?
- Stratum corneum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
What is a labile cell? Give an example
Active cells found in continuously dividing tissues e.g. epithelia including the epidermis
Where are stem cells found in the skin? What can they generate?
In the basal layer of the epidermis. They can generate hair follicles and the epidermis
What stage of the cell cycle are stable tissues in?
True or false: stable tissues can proliferate in response to injury?
Give an example of a stable tissue
Liver, kidney, pancreas, cells in the dermis i.e. endothelial cells, fibroblasts, smooth muscle cells
What type of cells synthesise the ECM?
Mesenchymal cells e.g. connective tissue, muscle, blood and lymphatic vessels
What type of cells produce/maintain cartilage?
Describe the blood supply to the skin
The blood supply to the skin is found in the dermis. There are superficial, mid-dermal and deep-dermal vessels. Nutrients diffuse from the superficial vessels into the epidermis, which has no blood supply.
What are some of the functions of the ECM?
- Mechanical support for tissues
- Substrate for cell growth and formation of tissue micro environments
- Regulates cell proliferation and differentiation
- Scaffolding for tissue renewal
- Storage and presentation of regulatory molecules e.g. growth factors
Which of these cells is not mesenchymal?
a) osteocyte b) epidermal cell c) chondrocyte d) fibroblast e) smooth muscle cell
b) epidermal cell --> mesenchymal
What is connective tissue?
The tissue that supports, binds or separates other tissues or organs
When must repair by connective (fibrous) tissue occur?
If there is damage to the connective tissue in addition to epithelial cells i.e. if the dermis is injured as well as the epidermis
What are non-regenrated cells replaced by during repair by connective tissue?
Fibrous (scar) tissue
What is the definition of an a) erosion b) ulcer?
- Erosion = mild injury to the epidermis and the basement membrane is still intact
- Ulcer = severe injury to the epidermis and dermis. The basement membrane is lost.