Pathology 6 - Cell ageing and death Flashcards
Mechanism that allow cells to cope with stress? (3)
HypertrophyHyperplasiaMetaplasia
What happens when stress becomes too much for a cell?
Cell death occurs
What are the 2 options of cell death?
NecrosisApoptosis
Does necrosis require energy?
No
Is necrosis physiological and/or pathological?
Always pathological
What are the 3 main types of necrosis?
Coagulative necrosisLiquefactive necrosisCaseous necrosis (mixture of the above 2)
What is coagulative necrosis?Usually caused by?What are dead cells consumed by?where is it often seen?
Type of necrosis where the cell outline is preserved for at least a couple of days usually caused by ischaemia or infarctiondead cells are consumed by various enzymatic processes and cells (microenvironment too toxic for proteolysis, etc.)Often seen in cardiac muscle - MI
What is liquefactive necrosis?Usually caused by?
Liquefactive necrosis (or colliquative necrosis) is a type of necrosis which results in a transformation of the tissue into a liquid viscous mass (no cell structure contains)Tissue is turned into pussOften it is associated with focal bacterial or fungal infections.Necrosis within the brain
What is another name for caseous necrosis?What is it usually associated with?What can it be considered as?
Cheesy necrosis - looks like cream cheeseTBA combination between coagulative and liquefactive necrosis
What is the characteristic appearance of TB?
Granulomatous inflammation with central caseous necrosis
What should be done if someone mentions caseous necrosis?
Think TB!!Ask for culture, PCR and look for result of Ziehl Neelson stain
What is apoptosis?
Programmed cell death in response to specific signals
Does apoptosis require energy?
Yes - it requires energy
What is necrosis?
the death of most or all of the cells in an organ or tissue due to disease, injury, or failure of the blood supply.
Is apoptosis physiological and/or pathological?
Physiological - we sometimes need cells to die off, it may be part of normal growthCan also be pathological
Example of physiological apoptosis? (apoptosis required for health)
Fingers initially start off webbed and then apoptosis creates distinct digits
Example of apoptosis related to immune system?
Removal of self reactive lymphocytes(another example of physiological apoptosis is hormone-dependant involution)
Examples of pathological apoptosis? (6) - sign of disease
In response to injuryRadiation (including UV light)ChemotherapyViral infection - hepatitisCancersGraft versus host disease
What are capsases?
Protease enzymes which play an essential role in apoptosis and inflammation
What are the 2 possible pathways for activating capsases?
ExtrinsicIntrinsic
What is the extrinsic pathway for activating capsases?
Death receptor (a TNF receptor/ Fas receptor) is activated when its ligand bindsWhen a number of these come together they form another receptor for a protein which also has a cytoplasmic “death domain” e.g. fas-associated death domainThis activates caspase
What is the purpose of Fas ligand?
Fas is a type of TNFSome cells of the body express a Fas ligand and activated T lymphocytes always express the Fas receptor meaning if they join, capsase is activated = apoptosis
What type of conditions do patients with Fas mutations often get?
Autoimmune diseases
What is tumour necrosis factor?
A cytokine released by many leukocytes which is involved in many processes such as inflammation and can cause cell death
What is another name for the intrinsic pathway of activating capsases?What is involved in this?
Mitochondrial pathwayGrowth signals promote anti-apoptotic molecules in the mitochondrial membraneWhen the growth signals are removed, they are replaced with apoptotic regulators (Bax or Bak)These increase the permeability of the mitochondria which causes the release of proteins, e.g. cytochrome C, that stimulate capsases
What are capsases?
Any number of compounds consisting of haems bound to a protein
What is p53?
A tumour supressor protein which binds to DNA and stimulates genes involved in suppressing division halting the cell cyclep53 binds to damaged DNA and if it can’t be repaired it induces apoptosis
What type of conditions can occur if there is too little apoptosis?
CancersAutoimmune disease
What type of conditions can occur if there is too much apoptosis?
Neurodegenerative disorders
What is the name for thethe irreversible condensation of chromatin in the nucleus of a cell undergoing necrosis or apoptosis?
Pyknosis
What morphological changes occur during apoptosis?
Pyknosis - Chromatin condensationCytoplasmic blebs (cytoplasm breaks up)Macrophages come in to hoover everything up
What is oxidative stress?
essentially an imbalance between the production of free radicals and the ability of the body to counteract or detoxify their harmful effects through neutralization by antioxidants
What causes cellular ageing?
Oxidative stress - free radical damageAccumulation of metabolism by-products e.g. lipofuscin
What is the name given to finely granular yellow-brown pigment granules composed of lipid-containing residues of lysosomal digestion. It is considered to be one of the aging or “wear-and-tear” pigments, found in the liver, kidney, heart muscle, retina, adrenals, nerve cells and ganglion cells?
Lipofuscin
What is the name of the structure at the end of a chromosome?What is the purpose of these?What do they consist of?What happens with every division?
TelomeresProvides protection and stops chromosome ends from degradation and fusionTTAGGG repeatsWith every division the number of repeats get smaller
What are somatic cells?
Any cell other than reproductive cells
Why do stem cells not die?
They contain telomerase that keeps adding more TTAGGG after its lost (telomerase is not active in somatic cells)
What is one factor that case stem cells to become immortal?
They reactivate telomerase
