Cellular Injury

Question 1

Cellular injury

Answer 1

-Most diseases begin with cell injury
-Cell unable to maintain homeostasis
-Injured cells may recover (reversible injury) or die (irreversible)

Question 2

Dependent factors of cellular injury

Answer 2

-Cell being affected: type, nutritional state, level of differentiation, level of susceptibility, adaptive process of the cell
-Injurious agent: type, severity, duration of the stimulus

Question 3

Mechanism of cell injury

Answer 3

-Hypoxia: lack of oxygen due to ischemia (low blood supply)
1. Vacuoles form in the mitochondria = low ATP
2. Na+/K+ pump of the cell membrane is disturbed: Na+ and Ca2+ into the cell, K+ flows out
3. Water follows = edema
4. Ribosomes detach from E.R. = protein synthesis diminishes
5. Reversible if oxygen is restored; if not = cell death

Question 4

Free radicals

Answer 4

-Electrically uncharged atoms having an unpaired electron; in an attempt to become stable, they form chemical bonds with other molecules

Question 5

Where do these free radical come from?

Answer 5

-Absorption of UV radiation, redox reactions (oxygen is reduced to water), enzymatic metabolism of chemicals/drugs

Question 6

Damaging effects of free radicals

Answer 6

-Lipid peroxidation (H2O2): increases membrane permeability
-Attacks critical proteins (affects ion pumps)
-Fragmenting DNA (affects protein synthesis)
-Damaging mitochondria (increases calcium cytoplasm)
-Certain antioxidants (vitamins s E, C, cysteine, etc) and certain enzymes can combat free radicals

Question 7

Chemical injury

Answer 7

-Biochemical interaction between a poison (toxin) and cell membrane
-General mechanisms of destruction: direct toxicity or formation of free radicals
-Ex: CCl4, arsenic, cyanide, CO, alcohol, lead, social drugs

Question 8

Injuries (intentional and unintentional)

Answer 8

-Blunt force, contusion, abrasion, laceration, bone fractures, stab wounds, puncture wounds, gunshot wounds, asphyxial injuries, drowning

Question 9

Blunt force

Answer 9

-Blows/impact causing tearing, shearing, crushing

Question 10

Contusion (bruise or hematoma)

Answer 10

-Blow that squeezes soft tissue causing bleeding underneath skin/underlying tissue

Question 11

Abrasion (scrape)

Answer 11

-Removal of superficial skin

Question 12

Laceration

Answer 12

-Jagged or irregular tear/rip

Question 13

Asphyxial injuries

Answer 13

-Suffocation, strangulation, chemical asphyxiants (CO, cyanide)

Question 14

Infectious injuries

Answer 14

-Caused by any microbial agent that can survive and thrive in the body (bacteria, virus, protozoan, fungus, helminths)

Question 15

Pathogenicity or virulence depends on

Answer 15

1. Ability to invade and destroy cells
2. Toxin production
3. Production of hypersensitivity reactions in host
4. Overall health of host (especially the condition of the immune system)

Question 16

Cellular injuries

Answer 16

-Cellular swelling due to water infiltration (affects ion pump)
-Abnormal accumulation of lipids and carbohydrates in cells (spleen, liver, CNS); glycogen (diabetes), proteins, pigments (melanin and hemoproteins), calcium, and urate (uric acid)

Question 17

Clinical manifestations of cellular injury

Answer 17

-Fever; acute inflammatory response
-Increased heart rate; increased metabolism due to fever
-Leukocytosis
-Release of cellular enzymes into extracellular fluid (type of enzyme depends)

Question 18

Cellular death

Answer 18

-Necrosis: dense clumping of DNA and disruption of plasma and organelle membranes
-Autolysis: cellular self-digestion
-Karyolysis: nuclear dissolution

Question 19

Types of necrosis

Answer 19

-Coagulative
-Liquefactive
-Caseous
-Fat
-Gangrenous

Question 20

Coagulative necrosis

Answer 20

-Due to hypoxia
-protein denaturation (albumin hardens)
-Occurs in kidneys, heart, and adrenal glands

Question 21

Liquefactive necrosis

Answer 21

-Ischemic injury to brain neurons
-Cells become digested by their own enzymes

Question 22

Caseous necrosis

Answer 22

-Pulmonary infection (usually tuberculosis)
-Dead cells disintegrate but leave cellular debris

Question 23

Fat necrosis

Answer 23

-Lipases destroy cells
-Breast, pancreas, abdomen

Question 24

Gangrenous necrosis

Answer 24

-Severe hypoxia
-Bacterial infection

Question 25

Apoptosis

Answer 25

-Programmed cell death
-Deletion of individual cells by fragmentation into membrane bound particles which are then phagocytized
-Both normal (needed for tissue turnover) and pathologic

Question 26

Aging

Answer 26

-Normal wear and tear due to accumulation of small microinsults caused by UV light, mechanical insults, and metabolic reactions
-Many theories on aging: genetic and environmental factors, degenerative extracellular changes, changes in cellular control mechanisms

Question 27

Somatic death

Answer 27

-Death of the entire person
-Postmortem change:
-Complete cessation of breath, circulation
-Falling body temp (algor mortis)
-Gravity causes blood to settle in lowest tissues causing purple color (livor mortis)
-Muscle stiffening starts within 6 hours (rigor mortis); entire body 12-14 hours
-Putrefaction 24-48 hours; then flaccid again
-Postmortem autolysis (microscopic putrefactive changes due to lytic enzymes)