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Death and Necrosis
LECTURE FOUR
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
Answer the following :Difference between
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
Contents
 Definition
 Death and Necrosis
 Macroscopic characteristic of death
tissues
 Causes of Necrosis
 Types of necrosis
 Fate of necrotic tissues
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
Definitions
 Necrosis: death of cells and tissues while the
body is whole still living.
 After a cell dies, lysosomes rupture and their
hydrolytic enzymes are released into the cell.
 The release and activation of these lysosomal
enzymes are largely responsible for cell
necrosis.
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
 Necrobiosis: The natural death of cells or
tissues through aging, as distinguished from
necrosis e.g.
 – Enterocytes
 – Kerotinocytes in the skin cells
constantly dying and being replaced
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
 Autolysis: The destruction of tissues or
cells by the action of enzymes, that are
produced within the cells. Also called
selfdigestion.
 Heterolysis: destruction of tissues or
cells by the action of enzymes from
outside of cells (neutrophils).
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
Dead and Necrosis
 Death refer to the complete cessation of vital
function of the cells and tissues and its include:
1- General (somatic) death
2- Local death which include:
 A- Physiological local death
(Necrobiosis) e.g. RBCs and squamous cell
after end of their life span.
 B- Necrosis.
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
Macroscopic characteristic of death tissues
 Regardless of necrosis or somatic death, death tissue is
characterized by the following:
 1- loss of its normal color, necrotic tissue tends to be lighter
in color (unless filled with blood, then darker); due to loss of
cytochrome oxidases.
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
 2- Loss of its elasticity, it become friable
and tend to rupture with mild mechanical
force.
 3- Autolysis, the destruction of tissues or
cells by the action of enzymes that are
produced within the cells.
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
 4- Putrefaction, due to invasion by
saprophytic bacteria.
 5- Presence of demarcation line
between necrotic tissue and normal
tissues (due to inflammation).
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
General causes of necrosis:
 Poisons and toxins:
 Chemical: Strong acids, alkalies, insecticides, mercury etc.
 Infectious agents: Bacteria (Salmonella, Staphylococcus), viruses,
fungi, protozoa etc.
 Plant poisons- hepatotoxic alkaloids .
 Circulatory disturbance: Anemia, congestion and ischemia.
 Mechanical injuries: Cutting, crushing and rubbing
types.
 Physical : Extreme temperature, electricity, free radical.
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
Causes of Necrosis
 Loss of blood supply (ischemia)
 Loss of nerve supply
 Loss of endocrine stimulation
 Endotoxin
 Mechanical/thermal injury
 Chemical injury
 Pressure
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
Gross appearance:
 Affected areas white, gray or yellow in
colour.
 Have a cooked meat appearance.
 Sharply demarcated (by red zone) from
healthy tissue.
 In case of gangrene the area is green, orange
or black ( iron sulphide)
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
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DR.ABDIAZIZ ABDI MOHAMED ABDI
3/10/2016
Nuclear changes:
Occur due to hydrolysis of nucleoproteins:
i. Pyknosis i.e. the nucleus becomes shrunken condensed and
deeply stained.
ii. Karyorrhexis: rupture of nuclear membrane with
fragmentation of the nucleus.
iii. Karyolysis: the nucleus dissolves and disappears.
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DR.ABDIAZIZ ABDI MOHAMED ABDI
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DR.ABDIAZIZ ABDI MOHAMED ABDI
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DR.ABDIAZIZ ABDI MOHAMED ABDI
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