Response to cell and tissue damage Flashcards
What is sublethal injury?
The loss of homeostasis and it is reversible but if uncorrected leads to cell death.
What are the two major types of sublethal injury?
Hydropic/oncosis (where the cell retains too much water)
Fat changes- steatosis (where there is a change in energy balance to the cell accumulates fat)
What is autophagy?
Where the cell walls off areas to be ‘eaten’
What is atrophy?
where the cell shrinks
What is the nature of injury determined by?
Whether it is acute or chronic, mild or severe and the cell type affected
what is necrosis?
Death of tissue following bioenergetic failure and a loss of plasma membrane integrity. It induces inflammation and repair
Name some causes of necrosis
Ischaemia, metabolic and trauma.
Name the different types of necrosis
Coagulative (necrosis in tissue),
Colliquative (necrosis in the brain),
Caseous (necrosis seen in tuberculosis),
Gangrenous (necrosis with rotting tissue),
Fibrinoid (necrosis in a microscopic feature of arterioles),
Fat necrosis (may follow trauma)
Describe Apoptosis?
Where individual cells are killed in a control manner and does not trigger inflammation. The cell is broken down into smaller membrane bound fragments which are then destroyed.
What are some variations of programmed cell death?
Pyroptosis
Ferroptosis
Necroptosis
What does reduced apoptosis cause?
Neoplasia, autoimmune disease and viral infections
what does increased apoptosis cause?
Neurodegenerative disorders, HIV infection of T lymphocytes.
Describe the differences between apoptosis and necrosis
Apoptosis - physiological or pathological, affects single cells, energy dependant fragmentation of DNA, membrane integrity is maintained, cells shrunk and broken into fragments, no inflammatory response triggered and the cells are phagocytosed.
Nercrosis - pathological, whole cell groups are effected, there is abnormal homeostasis, membrane integrity is lost, cell swells, inflammatory response triggered and its phagocytosed by inflammatory cells
Describe coagulative necrosis
Most common type which involves coagulation of cellular proteins.
Define coagulation
Where a liquid turns into a semi-solid gel
Describe colliquative
Liquefaction with formation of a cystic space in the brain.
Describe Caseous
Characteristic of tuberculosis, it is dead tissue with inflammation.
Describe Gangrenous
Necrosis with dead tissue
Describe Fibrinoid
Fibrin deposited in blood vessel walls
what is pyroptosis?
Part of apoptosis then necrosis. It is associated with samonella
Define labile, stable and permanent cells
Permanent - have a very limited capacity to replaced (neurons and skeletal muscles)
Stable - Not constantly turning over cells but do have the ability to regenerate if needed. (kidney and liver)
Labile - Always turning over cells so have a large capacity to regenerate (blood, gut and skin)
Describe healing by the first intention in the first week
- Limited cell death
- Basement membrane disrupted
- Incision space fills with blood
- Scab forms
- Neutrophils move towards clot
- Epidermis thickens at its cut edges
- epidermal cells migrate along cut margins of dermis
- Epithelial cells fuse in the mid line beneath the surface of the scab.
- Day 3 neutrophils largely replaced by macrophages
- Day 5 granulation tissue invades incision space
- Collagen fibres bridge the incision
- Epidermis recovers to normal thickness.
Describe first intention in the second week
During the second week, there is proliferation of fibroblasts, collagen accumulates and leucoytes infiltrate and oedema reduces. Vasculatarity virtually disappears.
Describe first intention by the end of 1 month
Scar consists of cellular connective tissue. Tensile strength now increases.
Describe healing by secondary intention
Occurs when there is extensive cell loss and there is a large tissue defect that must be filled. This results in more fibrin, more necrotic tissue and the inflammatory response is more intense. Wound contraction reduces size of defect, this can be characterised by the presence of myofibroblasts.
Describe briefly bone repair
Haematoma occurs at the break site, a callus is formed and then lamellar bone is laid down.
factors that influence bone healing are?
Systemic; age, nutrition, metabolism, circulatory status and hormones
Local; infection, mechanical factors, foreign bodies, size and location and the type of wound
Poor scar formation can occur why?
Due to dehiscence (wound bursts open) and ulceration (where there is not enough circulation)
What occurs when there is an excessive formation of repair components?
Keloid scar - excessive fibroblast proliferation and collagen production
