2. Cell cycle
2
New cells are formed
from the existing cell
The cell is produced
by duplicating the
existed one and then
they will divide in to
two
This event is called as
cell cycle
3. Cell death
The body is very good at maintaining a constant number
of cells so there has to exist mechanisms for ensuring
other cells in the body are removed when appropriate
Cell death happens in two forms
◦ Apoptosis – suicide – programmed cell death
◦ Necrosis – killing – decay and destruction
3
5. Necrosis
Necrosis is the death of
body tissue. It occurs when
too little blood flows to the
tissue. This can be formed by
injury, radiation, or
chemicals.
Necrosis cannot be
reversible
These are dead cells shows
changes in both cytoplasm
and in the nucleus
5
6. Nuclear and cytoplasm
6
Cytoplasmic changes Nuclear changes
Increases eosinophilia, glassy
appearace granular or vacuolated
cytoplasm, swellen mitochondria
may also show calcification
Karyolysis - complete
dissolution of chromatins
Karyorrhexis – chromatin is
distributed irregularly
Pyknosis – irreversible
condensation of chromatins
7. Factors
7
NECROSIS MAY OCCUR DUE TO
EXTERNAL AND INTERNAL
FACTORS
EXTERNAL FACTORS MAY
INVOLVED
MECHANICAL TRAUMA (
PHYSICAL DAMAGE TO THE BODY
THAT CAUSES CELLULAR BREAK
DOWN)
DAMAGE TO BLOOD VESSELS
(WHICH MAY DISRUPT BLOOD
SUPPLY TO ASSOCIATED
TISSUE)
THERMAL EFFECT (EXTREMELY
HIGH OR LOW TEMPERATURE
CAN RESULT IN NECROSIS DUE
TO DISRUPTION OF CELLS
8. Causes
Internal factors causing necrosis includes
1. Trophoneurotic disorders - injury and paralysis of nerve cells
2. Pancreatic enzyme – are the major cause for the fat necrosis
(lipases)
3. Immunological barriers – invasion of pathogen through
surface affected by inflammation (intestinal mucosa)
4. Bacterial toxins – activated natural killer cells and peritoneal
macrophages
5. Toxins and pathogens – may cause necrosis toxins such as
venom may inhibit enzymes and cause cell death
8
9. Necrotic cell death
LOSS OF METABOLIC FUCTION
LOSS OF INTEGRITY OF THE CELL MEMBRANES
CESSATION OF THE PRODUCTION OF PROTEIN
CELL ORGANELLS SWELL AND BECOMES NON-FUNCTIONAL
9
10. Mechanisms of necrosis
Depletion of ATP leads to breakdown of the cells ion balance
Reduce oxygen level (hypoxia)
Oxidative stress the presence of the excess oxygen radicals
10
12. Coagulation
necrosis
This types necrosis is
seen in every tissues
except brain
They occurs due to the
loss of blood
Cell outlines are
preserved and
everything looks red
12
13. Liquefaction necrosis
13
This type of necrosis occurs as infection in
brain infarcts
Due to lots of neutrophiles around releasing
their toxic contents “liquefying” the tissue
Tissue is liquidly and creamy yellow (pus)
Lots of neutrophils and cell debris
14. Fat necrosis
Fat necrosis that in which the neutral fats in
adipose tissue are split into fatty acids and
glycerol usually affecting the pancreas
Shadowy outline of dead fat cells
14
15. Caseous necrosis (lungs)
Cheesy necrosis that in which the tissues is soft dry and
cottage cheese-like :most ofte seen in tuberculosis and
syphilis
15
16. Gangrenous necrosis
See this when an entire limb loses blood supply
and dies
Skin looks black and dead:underlying tissues is in
varying stages of decomposition
Dry gangrene Initially there is coagulative
necrosis from the loss of blood supply
wet gangrene If bacterial infection is
superimposed there is liquefactive necrosis
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17. Fibrinoid necrosis
Fibrinoid necrosis is a specific pattern of
irreversible, uncontrolled cell death that occurs
when antigen-antibody complexes are deposited
in the walls of blood vessels along with fibrin
see this in immune reactions in vessels
Complexes of antigen and antibodies
It appears as too small and visible grossly
Vessel walls are thickened and pinkish red
fibrinoid
17
18. Apoptosis
Programmed cell death
In human body cells were produced every second by mitosis there is a
similar number die by apoptosis
Between 50-70 billion cells die each day in adult
Between 20-30 billion cells die each day in child
18
19. Programmed
cell death
It is a form of cell death in which a suicide program is
activated within cells
Which leads to
Fragmentation of the DNA
Shrinkage of the cytoplasm
Membrane changes and cell death without lysis or damage to
neighboring cells
19
20. Characteristics
of apoptosis
It is a normal phenomenon occurring frequently in a
multicellular organism
A cell that undergoes apoptosis dies neatly without
damaging its neighbour cells
The cell will shrink and then condensed
There will be no inflammation in apoptosis
20
21. Importance of apoptosis
Programmed cell death is needed to destroy cells that represent a threat to the
integrity of the organism
Examples :
Cells infected with viruses
Cells with DNA damage
Cancer cells (uncontrolled proliferated cells)
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23. Mechanisms of apoptosis
Apoptosis occurs in two phases :
1. Initiation phase: It happens when apoptotic enzymes are
getting activated
2. Executive phase: activating enzymes are cause cell death
Initiation phase :
1. Extrinsic pathway
2. Intrinsic pathway
23
25. Extrinstic pathway
It is called as death receptor pathways mediated by death receptor
Caspase are (cysteine – aspartic acid) specific proteases that mediates the events that are
associated with programmed cell death
25
26. Executive phase
it is mediated by caspase 3 and caspase 6
When it is activated they form sequence chain of reaction than can activates caspase 3 and 6
They break down cytoskeleton protein and neuclear matrix that result in the breaking of the
nucleus
26
29. Basic concept in mechanism
Cellular stress activates autophagy pathway
29
Phagophore
formation
• Isolation membrane
• Derived from endoplasmic recticulum plasma membrane or mitochondria
Autophagos
ome
• Formation of vesicles
autophago
lysosome
• Fusion with lysosome
30. mechanism
Autophagy related genes which encodes protein called ATG protein
ATG proteins needed for the formation of autophagosomes
Depletion of growth factors activates
This ULK1 complex is called as initiation complex so this complex initiates the
process of autophagy
This forms preautophagosomal structure
30
ATG101
ATG13
ULK1
31. Mechanism
31
ATG14L
VPS15
BECLIN 1
VPS34
That ULK1 complex activates
This complex is called as PI3K complex
This stage is called as nucleation
This activation of PI3K complex results in nucleation and formation of phagophore
Phagosome formation
32. Elongation and maturation
This has to elongate and fuse to form Autophagosome
For that they need a set of proteins called as ubiquitin like conjugation system
The function of ubiquitin is identifying proteins to be degraded by the proteasome,
but ubiquitination can play a role in other processes such as endocytosis and other forms
of protein trafficking, transcription and transcription factor regulation, cell signaling,
histone modification, and DNA repair.
Ubiquitin like system covalently links lipid in phosphatidylethanolamine to the
microtubule-associated protein light chain 3 (LC3) results in elongation and the fusion to
form autophagosome
During the process of autophagosome the cellular content will be trapped inside
autophagosome
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34. Benefits of
autophagy
Its is a survival mechanism under stressful conditions
It maintains the integrity of cells by recycling essential
metabolites and clearing intracellular debris
Intracellular debris occurs in aging , under stress and in
diseased state
When such cell unable to cope the cell which is already in
autophagy so autophagy itself trigger death
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35. Roles of autophagy
IN CANCER :
In cancer cells, autophagy suppresses tumorigenesis by inhibiting
cancer-cell survival and inducing cell death, but it also facilitates tumorigenesis
by promoting cancer-cell proliferation and tumor growth .the mechanism of the
autophagic process is controlled by a series of proteins
35
36. ROLES OF AUTOPHAGY
ROLE OF AUTOPHAGY IN NEURODEGENARATIVE DISEASE
Increasing evidence suggests that dysregulation of autophagy results in the
accumulation of abnormal proteins and/or damaged organelles, which is
commonly observed in neurodegenerative diseases, such as Alzheimer,
Huntington's, and Parkinson's diseases (Banerjee et al
36