Cell injury
 A person’s state of wellness and disease is reflected in
the cells.
 Injury to any of the cell’s components can lead to
illness.
 Consider, for example, a patient with HIV. The cells of
the immune system may be altered, making the
patient susceptible to infection.
Draw on your reserves, adapt, or
die
 When cell integrity is threatened (toxins, infection,
physical injury, or deficit injury), the cell reacts in one
of two ways:
 • by drawing on its reserves to keep functioning
 • by adapting through changes or cellular dysfunction.
 If enough cellular reserve is available and the body
doesn’t detect abnormalities, the cell adapts. If there
isn’t enough cellular reserve, cell death (necrosis)
occurs.
 Necrosis is usually localized and easily identifiable.
I. Toxic injury
 Causes may be endogenous or exogenous factors
 Common endogenous factors include:
 genetically determined metabolic errors,
 gross malformations, and
 hypersensitivity reactions.
Exogenous factors include:
alcohol,
lead,
carbon monoxide, and
drugs that alter cellular function.
II. Infectious injury
 Viral,
 fungal,
 protozoan, and
 bacterial agents can cause cell injury or death.
 Infectious organisms affect cell integrity, usually by :
 interfering with cell synthesis, producing mutant cells.
 For example, human immunodeficiency virus alters the
cell when the virus is replicated in the cell’s RNA
III. Physical injury
 Results from a disruption in the cell or in the
relationships of the intracellular organelles.
 Two major types of physical injury are:
 thermal (electrical or radiation); include radiation
therapy for cancer, X-rays, and ultraviolet radiation
 mechanical (trauma or surgery); include motor vehicle
crashes (RTA) and ischemia
IV. Deficit injury
When water, oxygen, or nutrients
decrease , or if temperature changes
and waste are accumulated, cellular
synthesis can’t take place.
A lack of just one of these basic
requirements can cause cell
disruption or death.
Conditions of Disease or Injury
 1-Hypoxia
 Hypoxia is the decreased concentration of oxygen in
the tissues.
 What is the difference bwn hypoxia & hypoxemia?
 Cells and tissues become hypoxic when there is:
 inadequate intake of oxygen by the respiratory system,
 inadequate delivery of oxygen by the cardiovascular
system,
 or a lack of Hgb.
Oxygen is required by the mitochondria for production of
ATP.
Consequences of Hypoxia
 cell begins to swell and burst, because Na diffuses into
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the cell and withdraw water.
production of lactic acid, decreased pH causes
damage to the nuclear structures.
The effects of hypoxia are reversible if oxygen is
returned within a certain period of time, the amount
of which varies and depends on the tissue.
Signs & Symptoms:
- Tachycardia.
- Tachypnea.
- Muscle weakness.
- Decreased level of consciousness.
Complications
 - If cerebral hypoxia prolongs , consciousness may
deteriorated to coma and death.
 -Organ failure, including: ARDS, CF, or renal failure,
may occur if hypoxia is prolonged.
 Treatment: Increase oxygen in inspired air through a
mask or mechanical ventilation.
2-Temperature Extremes
 - Very high temperatures can cause burn injuries (direct death)
or cause coagulation of blood vessels or cell membranes
breakdown (indirect death) .
 - Very cold temperatures can injure cell in two ways:
vasoconstriction (inadequate nutrients and oxygen to the
extremities), and the formation of ice crystals (directly damage
the cells and can lead to cell lysis and bursting).
 Prolonged exposure to the cold can lead to hypothermia.
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Signs & symptoms:
- Numbness or tingling of the skin or extremities.
- Pale or blue skin that is cool to the touch.
- Shivering early on, then lack of shivering as condition worsens.
- Decreased level of consciousness, drowsiness, and confusion.
2-Temperature Extremes
 Complications
 - Blood clotting, characterized by pain and a decrease
in pulse downstream from the clot.
 If blood flow is inadequate for an extended time,
gangrene may result.
 - Frostbite.
 - Ventricular dysrhythmia
3-Radiation Injury
 Radiation energy may be higher or low energy.
 High-energy radiation (UV radiation) is called ionizing
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radiation, may injure or kill cells directly by destroying the
cell membrane and causing intracellular swelling and cell
lysis
As cells are killed or injured, the inflammatory response is
stimulated; capillary leakiness, interstitial edema, WBCs
accumulation, and tissue scarring.
It may also lead to mistakes in DNA replication or
transcription which may cause programmed cell death or
subsequent cancer .
Most susceptible cells are that undergo frequent divisions,
gastrointestinal (GI) tract, the integument (skin and hair),
and the blood-forming cells of the bone marrow.
Ionizing radiation is emitted by the sun, in x-rays, and in
nuclear weapons.
3-Radiation Injury
Low-energy radiation is called non-ionizing radiation.
Ionizing radiation.
 Non-ionizing radiation includes microwave and US
radiation.
 The energy of this radiation is too low to break DNA
bonds or damage the cell membrane.
3-Radiation Injury
 S &Sx of Ionizing Radiation
 - Skin redness or breakdown.
 - With high doses, N & V caused by GI damage.
 - Cancer may develop years after the exposure .
 - Anemia if the bone marrow is destroyed.
 Pediatric Consideration
 Fetal cells rapidly undergo cellular division and are highly
susceptible to the damaging effects of ionizing radiation.
Infants and young children also experience periods of rapid
cellular growth and are at risk of genetic damage from
ionizing radiation. Studies suggest that there are no
apparent health risks to fetuses exposed to non-ionizing
radiation .
4-Injury Caused by Microorganisms
 Cells of the body may be destroyed directly by the MO or
by a toxin released from the MO, or may be indirectly
injured as a result of the immune and inflammatory
reactions .
 S & Sx:
 Infection by bacteria and viruses, often results in:
 - Regional lymph node enlargement
 - Fever (usually low-grade with a viral infection)
 - Body aches
 - Skin rash or eruption, especially with viral infections
 - Site-specific responses, such as pharyngitis, cough, otitis
media
4-Injury Caused by Microorganisms
 Rx:
 - Bacteria and mycoplasmas are treated with AB,
preferably after C& S.
 - Certain viral infections may be treated with antiviral
agents. Other viral infections usually are left to resolve
on their own, with care taken that a subsequent
bacterial infection does not infect the original site or
elsewhere.
Cell degeneration
 Degeneration; nonlethal damage of the cell , generally occurs in
the cytoplasm of the cell, while the nucleus remains unaffected.
 Degeneration usually affects organs with metabolically active
cells, such as the liver, heart, and kidneys.
 Causes:
• increased water in the cell or cellular swelling
• fatty infiltrates
• atrophy
• autophagocytosis, during which the cell absorbs some of its own
parts
 •pigmentation changes
When changes within cells are identified, degeneration may be slowed
or cell death prevented through prompt treatment.
subclinical identification; a disease is diagnosed before the patient
complains of any symptoms.
Unfortunately, many cell changes remain unidentifiable even under a
microscope, making early detection impossible.
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Cell aging
 Normal process of cell aging; cells lose structure and
function.
 Lost cell structure may cause atrophy.
 Two characteristics of lost cell function are:
 • Hypertrophy, an abnormal thickening or increase in
bulk
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Hyperplasia,
 Cell aging may slow down or speed up, depending on
the number and extent of injuries and the amount of
wear and tear on the cell
 Warning: This cell will self-destruct
Cell aging
 Signs of aging occur in all body systems. Examples of
the effects of cell aging include
 decreases in elasticity of blood vessels, bowel motility,
muscle mass, and subcutaneous fat.
 The cell aging process limits the human life span. One
theory says that cell aging is an inherent self
destructive mechanism that increases with a person’s
age.
 Cell death may be caused by internal (intrinsic) factors
that limit the cells’ life span or external (extrinsic)
factors that contribute to cell damage and aging.
Cell Death
 There are two main categories of cell death:
 1-Necrotic cell death, characterized by cell swelling and
rupture of internal organelles.
 Common causes of necrotic cell death include prolonged
hypoxia and infection .
 2- Apoptosis, is not characterized by swelling or
inflammation, but rather the dying cell shrinks on itself
and then is engulfed by neighboring cells.
 Programmed cell death begins during embryogenesis and
continues throughout the lifetime of an organism.
 Viral infection of a cell will often turn on apoptosis,
ultimately leading to the death of the virus and the host
cell. Deficiencies in apoptosis have been implicated in the
development of cancer .
Results of Cell Death
 Dead cells are removed from the area or isolated from the
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rest of the tissue by immune cells in the process of
phagocytosis.
If mitosis is possible and the area of necrosis is not too
large, new cells of the same type fill in the empty space.
If cell division is impossible or if the area of necrosis is
extensive, scar tissue will form in the vacated space
Gangrene refers to the death of a large mass of cells.
Gangrene may be classified as dry or wet.
 Dry gangrene spreads slowly with few symptoms and is
frequently seen in the extremities, often as a result of
prolonged hypoxia.
Results of Cell Death
 Wet gangrene is a rapidly spreading area of dead tissue,
often of internal organs, and is associated with bacterial
invasion of the dead tissue. It exudes a strong odor and is
usually accompanied by systemic manifestations
 Gas gangrene is a special type of gangrene that occurs in
response to an infection of the tissue by a type of anaerobic
bacteria called clostridium.
 It is seen most often after significant trauma. Gas gangrene
rapidly spreads to neighboring tissue as the bacteria release
deadly toxins that kill neighboring cells. This type of
gangrene may prove fatal.
Wound Repair
 Destroyed or injured tissues must be repaired by
regeneration of the cells or the formation of scar
tissue.
 The goal is to fill in the areas of damage.
 Tissues that heal cleanly and quickly are said to heal
by primary intention. Large wounds that heal slowly
and with a great deal of scar tissue heal by secondary
intention. Several factors can delay healing, such as:
malnutrition, systemic disease, poorly functioning
immune system or if there is reduced blood flow to the
injured tissue or if an infection develops.