Cell Injury and cell death Flashcards
(30 cards)
What are the 3 situations when you get reversible cell injury?
- decreased oxidative phosphorylation
- decreased ATP production
- decreased cell integrity resulting in cell swelling
Describe how a normal cell and a hypoxic cell differ with cell swelling
- in a normal cell, there is ATP used to work the Na/K pump, which pumps 3Na out of the cell and 2 K into the cell. If there was an unbalance in this, then water would follow the concentration gradient
- in a hypoxic cell, there is a decreased amount of o2 so there is less oxidative phosphorylation that will occur. With less O2 the cell has to depend on anaerobic glycolytic pathway to produce energy. This produces less ATP then oxidative phosphorylation and it also uses up all of the glycogen stores and results in excess lactic acid production. Since there is less ATP production, then there is a decreased ability to make the Na/K pump function normally so the 3 Na stays in the cell and the 2 K stays outside the cell. Since there are more molecules inside the cell, water moves into the cell, causing cell swelling. Additionally, there will be damage to the cell membranes, resulting in the destruction of the selectively permeable barrier, which will allow the product of cell metabolism to enter the cell.
What is another name for acute cell swelling? describe it
- Hydropic degeneration.
- when there is an increased in cell size and volume because there is an increased amount of water within the cell. this results in the modification and degeneration of organelles and the break down of cell membranes
What are the gross changes in a swollen cell? Microscopic?
- swollen, heavier and more pale than normal
- may have cloudy swelling, hydropic degeneration or ballooning degeneration (cells greatly enlarged and clear) and lipidosis (accumulation of excessive intracellular lipid filled vacuoles
What are some ultrastructural changes to a reversible cell injury?
- plasma membrane alterations like blabbing, loosening of intercellular attachments
- mitochondrial swelling
- dilation of ER
What are some clinical examples of reversible cell damage?
- pox virus causing epidermal injury
- ruminal acidosis
- hepatic lipidosis
- steroid hepatopathy
describe pox virus causing epidermal injury
the virus affects the epidermal cells and causes degradation of the cytoplasmic proteins and a net flux of water into the cytoplasm. This causes cell swelling, which progresses to ballooning degeneration, forming blisters from the lysing of individual epidermal cells
describe ruminal acidosis
ruminant consumes carbohydrate rich feed, which alters the bacterial composition within the rumen to gram positive bacteria. This causes a decrease in pH, killing the normal microflora in the gut. Then water from the blood moves into the rumen to try and dilute out the feed, and this causes dehydration of the animal. If the animal survives, it will have stellate stars in its rumen - or the animal will die
describe hepatic lipidosis
what does the liver look like?
- this occurs with obese animals or animal that have good body condition but are unable to eat for a prolonged period of time
- the body runs out of protein to use for energy so the body starts mobilizing its free fatty acids, which move into the blood to travel to the liver. Since there is a lack of energy in the animal’s system, there isn’t energy to catabolize the ffa into TAGs. Additionally, there is no way to remove the triglyercides that are in the liver because there is a lack of apoproteins which are needed. therefore, the ffa and the TAGs are trapped in the liver. this makes the liver develop a diffuse yellow colour, makes it friable, greasy and able to float if it was put in formalin.
describe steroid hepatopathy
what does the liver look like
-this happens when there is long term administration of corticosteroids. The steroids cause glycogen to accumulate in the hepatocytes.
it will appear bronze colour, will not be friable or greasy and will not float if it is placed in formalin
what are the two types of irreversible cell injury?
- necrosis
2. apoptosis
What is necrosis?
it is the death of cells within a living animal. it is alway pathological.
it causes severe damage to the cell membrane when lysosomal enzymes enter the cytoplasm, digest the cell and allow its organelles to leak out.
the leaking of intracellular enzyme causes damage to the surrounding tissue and initiates an inflammatory response
what two enzymes leak out of the cytoplasm of the cell and can be detected in blood?
-creatinine kinase (from muscle) and ALT (from liver)
With necrosis, what does the influx of Ca do?
- activated phospholipase A which breaks down the phosphlipids in the mitochondria
- generates arachidonic acids, which initiates inflammation
- activates proteases, which damages the cytoskeleton and membrane, making the membrane more damaged
how do necrotic cells appear
grossly: pale, firm, swollen or shrunken
micro: nucleus is pushed to the side and it will be pyknotic, karyolytic or karyohexic
What are the 5 types of necrosis?
- coagulation necrosis
- liquidative necrosis
- caseous necrosis
- gangrenous necrosis
- fat necrosis
Describe coagulation necrosis
- most commonly occurs because of hypoxia to the cells, but it may also be due to toxins.
- tissue has its original structure but is pale, swollen, firm and more friable than normal tissue
- nucleus normally lysis
describe liquifactive necrosis
- typical type of necrosis that occurs in the brain - malacia
- in other tissues it is a pyogenic bacterial infection that results in the release of enzymes from the neutrophils that have accumulated, the lysing of the tissue and the formation of pus.
- if the pus if not removed, it is walled off by a fibrous capsule and is then called an abscess. If this abscess persists then the interior part becomes more caseous and there are multiple layers of fibrous capsule and this makes an “onion ring”
describe caseous necrosis
-introduction of a specific bacteria or a fungus and macrophages are used to try and remove it.
-conversion of nuclear and cytoplasmic debris in the dead tissue into granular friable mass and if it is surrounded by fibrous capsule it is called a granuloma
it is a more chronic lesion
What are the different types of gangrene? describe them
- Dry gangrene: coagulation necrosis of distal extremities followed by mummification. It can be caused by ingesting toxins (ergot - causes vasoconstriction), frost bite (decreased vascular flow) or septicaemia
- Wet gangrene: dry gangrene with secondary bacterial infection.
- gas gangrene: infecting bacteria are within the necrotic tissue and start producing gas bubbles (ex black leg - bacteria are introduced via intestines but they migrate to the muscle and wait for trauma or necrosis to occur and then they produce anaerobic conditions and form gas bubbles)
describe fat necrosis
necrosis within body fat stores. result in the formation of white/ chalky areas surrounded by inflammatory cells
What is the purpose of necrosis?
what happens if it doesn’t work
the goal is to digest and liquify the necrotic tissue so that it can be removed and replaced with new, functional tissue.
-if necrosis isn’t removed than it may become dystrophic calcification
Name the various types of postmortem changes one can see
- rigor mortis -ATP and glycogen are depleted so unable to reverse the contraction of muscle
- liver mortis - red discolouration of dependent areas. blood settling with gravity.
- postmortem clotting - clot will not be attached to the vessel but will be a replica of the inside of the vessel. the clot will divide with the RBC settling to the bottom and the serum staying closer to the top - chicken fat clot
- hemoglobin imbibition - red staining of tissue from blood cells
- bile imbibition -bile seeping out of the gall bladder and staining the surrounding tissue green
- Pseudomelanosis -blue-green discolouration from iron sulphide
- bloating - post mortem gas production from bacteria in the rumen
- postmortem emphysema - gas production of bacteria from GIT shortly before death
- mucosal sloughing - in rumen a few hours before death
Describe apoptosis
- physiological or pathological cell death on an individual level.
- the cells that are destined to die activate enzymes that will degrade the cells own nuclear DNA and cytoplasmic proteins. This alters the cells structure making it a target for apoptosis - without any inflammatory response
