Download Sheet#2,Dr.Nisreen, Noor Tahboub

17-9-2013
pathology-lec 2
Noor Tahboub
There are two types of cell injury:
1- reversible
2-irreversible
Slide 1: Reversible cell injury
We said last lecture that the cell tries before reaching the injury stage to adapt with the new
environment that surrounds it to avoid being injured and later on death.
There is a point at which the cell is no longer able to adapt or the adaptation that it does is not
enough to overcome the toxic or injurious stimulus so reversible type of cell injury begins.
Types of reversible cell injury:
1-cellular swelling
2-fatty change
Question: What determines if the cell injury is reversible or irreversible?
The two main structures that make the cell are the nucleus and the cell membrane so if any of
these structures is damaged or injured,the injury will be considered as irreversible.
Because,No nucleus means No DNA so No chance to transcript any protein and No mitosis then No
Cell !
Also,the cell membrane is the boundary of the cell so if there's no membrane(either plasma
membrane or organelle membrane),there will be No boundaries so No Cell !
**Any other injury is considered as reversible injury as long as we removed the stimulus that caused
the injury then the cell can return to the recovery stage.
Slide 2 :
Cellular Swelling:
-characterized by accumulation of fluids or water inside the cell. This fluid will be in clear vacuoles in
the cytoplasm so microscopic examination will show numerous small clear vacuoles within the
cytoplasm.
**Note :anything contains water is called "hydropic"
Fatty Change:
In this type, we find vacuoles of fat inside the cell instead of fluid .It is seen in cells involved in fat
metabolism like hepatocytes(liver cells)and myocytes(cardiac muscle cells).
1
17-9-2013
pathology-lec 2
Noor Tahboub
Note:Adipocytes are involved in fat storage but hepatocytes are involved in fat metabolism.
Slide 4: The Diagram
We have 3 panels; normal,reversible and irreversible injured cell
In the normal cell:
1-the plasma membrane is regular
2-the nucleus is clear
3-chromatin is open (no condensation)
4-all the organelles are perfect
In the reversible injured cell: under microscope we will see morphological changes or subcellular
alternations in the cell,for example:
1-membrane blebs in plasma membrane (disruption of the normal shape of the membrane) BUT No
destruction of the membrane so far
2-swelling in the different organelles especially in the mitochondria and the ER as a result of fat
accumulation.
3- clumping (condensation) of chromatin BUT still No destruction in the nucleus.
Slide 5 : Irreversible Injury
It has 2 types: Apoptosis and Necrosis
**Note:irreversible cell injury means cell death.
Question: What is the difference between apoptosis and necrosis?
Apoptosis: programmed cell death.A certain cell in a certain tissue at a certain time must die and
this is known before the creation of the cell.
This depends on the cells type,location,if it is mature or not,if it is primitive or stem cell and many
other factors.
On the other hand,Necrosis is the death of the cell due to injurious stimuli.It is almost always
pathological.
**Note: What maintains the survival to the plasma membrane and nucleus is the ATP.The cell must
always have a source of energy to maintain its shape and function.If there is no ATP production
there will be No oxidative phosphorylation then disruption of phospholipid junctions in plasma
membrane and damage to the DNA.
2
17-9-2013
pathology-lec 2
Noor Tahboub
Slide 7: Cellular features of necrosis and apoptosis
According to the diagram:
In apoptosis,the changes are not random because the process is programmed not haphazard.The
changes are:
1-regular damage or cleavage of the DNA by a certain enzyme into small fragments called
"nucleosome-sized fragments"
2-cleavage at certain points in the plasma membrane which results in fragments of plasma
membrane contain cytoplasm.These fragments are called "apoptotic bodies".
**the whole big cell now consists of many fragments,each one is called apoptotic body filled with
cytoplasm,part of organelles and surrounded by part of the plasma membrane.
**Note:Apoptosis happens due to physiologic causes.(No inflammation or infection, no stimulus,no
toxic or chemical material)
In necrosis, almost always pathological (which means there is stimulus like
hypoxia,ischemia,radiation,toxic or chemical agent )
The changes are: random destruction to the nucleus and plasma membrane result in fragmentation
of the cell.
**One of the main organelles inside the cell is the Lysosomes which contain digestive enzymes so
destruction of these structures will lead to leakage of these enzymes into the cytoplasm then
further disruption of different organelles in the cell. So this enzymatic digestion and leakage of cell
contents will lead to cell death.
Slide 11: Morphology of necrosis
1- Increased eosinophilia
The normal cell has somewhat bluish color in the cytoplasm due to the presence of ribosomes,ER
and mRNA.
In necrosis,these structures that give basophilia to the cell are damaged so the cell becomes pink in
color(eosinophilia)
**Note:eosinophilia is derived from the stain "eosin".
basophilia is derived from the term "basic".
2-Myelin figures: fragments of membrane either from the plasma membrane or organelles
membrane so inside the cytoplasm after cell death.
3
17-9-2013
pathology-lec 2
Noor Tahboub
3- Calcification :fatty acids residues result in the generation of calcium soaps.
Slide 14: Nuclear dissolution assumes one of 3 patterns
Karyolysis, Pyknosis and Karyorrhexis are random destruction of chromatin..we see them only in
Necrosis.
-Karyolysis :DNase cleaves the DNA so basophilia of the chromatin fades.
-Pyknosis :nucleus shrinks in size and the DNA condenses so it becomes very dark in color(early
stage before complete destruction of nucleus )
-Karyorrhexis: comes after Pyhnosis,the pyknotic nucleus undergoes fragmentation.
Slide 15: Patterns of Tissue Necrosis
To study the effect of injury on organ.
We have 6 patterns of tissue necrosis :
1- Coagulative necrosis
‫ تخثر‬، ‫تجلط‬
_destruction of nucleus but the basic cell shape and the cell outline is preserved.How?
the cell dies quickly so we can see a ghost of cell in its original space(under microscope we can tell
that there was a cell in that space but now it is dead).
Example:myocardial infarction
‫احتشاء عضلة القلب‬
the most common cause of MI is hypoxia and ischemia.If sclerosis in coronary arteries happens
,there will be sudden loss of oxygen supply to the cardiac muscles then cells death.
**Infarcts:ischemic necrosis of any tissue (loss of blood supply to any organ )
**Note:the brain doesn't undergo the coagulative type of necrosis because it is not solid.
-It is seen in solid organs organs like heart,liver,kidney,muscles and bones.
2-liquefactive necrosis
The term "liquefactive" is derived from "liquid"
Water content in brain is more than 85% so when necrosis happens in brain ,the fluids will
accumulate so undergo liquefactive necrosis.
Another Example:pus
4
17-9-2013
pathology-lec 2
Noor Tahboub
‫الخراج‬-‫الصديد‬-‫الدمل‬-‫القيح‬
-bacterial infection triggers inflammation.
3-caseous necrosis
the term "caseous" is derived from (cheese-like):yellowish cheesy material at the center of necrotic
tissue.
Example: tuberculosis
4-fat necrosis
-happens in adipose tissue
-seen in acute pancreatitis…why pancreas ?
because the pancreas is in the abdomen and the abdomen is covered by mesenteric fat so in cases
like severe acute pancreatitis,the pancreatic enzymes will leak and go inside the other tissues that
surround the pancreas like mesenteric fat and they digest it(fat necrosis)
5- gangrenous necrosis
-blackish discoloration of dead tissues.
-usually seen in diabetic foot,trauma
-It resembles the coagulation type because gangrene is infarct .Gangrene happen because there is
no blood supply (ischemia) so it undergoes at first coagulative necrosis.
Gangene is simply coagulation necrosis but it involves multiple tissue layers(not only one type of
cells )
Gangrene in diabetic foot affects skin+ subcutaneous tissues+muscles even the bone.
-Types:dry and wet
Question: What determines if the gangrene will remain dry or it will turn to wet gangrene?
the infection …all gangrene begins as dry..if it get infected,it will turn to wet(it will have fluids due
to bacteria)
-so wet gangrene is coagulative necrosis that happen in dry gangrene +superimposed liquefactive
action of bacteria.
6-fibrinoid nicrosis
-Not that important
-It is seen in blood vessels.
Vasculitis: inflammation of the wall of the blood vessel.
5
17-9-2013
pathology-lec 2
Noor Tahboub
Slide 21:
Liquefactive necrosis:We have a picture for a brain of a patient who died with stroke.When his brain
was open,the fluids came out.
Caseous necrosis: We have a picture for a lung of a patient who died from tuberculosis.We see
cheesy yellow color in the lung.
Slide 22:
fat nicrosis:small points whitish in color
**Note:in fat necrosis,calcium salts bind with free fatty acids in a process called saponification and
this gives the white color.
Fibrinoid nicrosis:blood vessels undergo this type of nicrosis(vasculitis)
Slide 23:
It is a picture for a small intestine of a patient represented with severe abdominal pain.
The normal intestine is pinkish in color but the red one is not normal(infracted) so it is coagulative
nicrosis.
Slide 24:
Gangrene frequently involves the peripheral circulation like hands and feet because they have good
circulation.
It is a dry gangrene because nobody told us that there is infection or we don't see signs of
infection(no pus).
Slide 25:
discoloration of the whole limb from toe to knee and there is pus so it is wet gangrene.
NOTE:I didn't mention all the information that are in slides unless there is extra information about
them..so be careful to study both the sheet and slides..
Good luck 
6