Unit 2 - 2.8-2.9 Flashcards
In a nutshell: Necrotic tissue in a live animal can be modified by environmental effects, allowing it to decompose in particular ways
gangrene
Where does dry gangrene occur?
in tissues that have a relatively limited amount of blood and fluids
Give some examples of where you’d see dry gangrene (5):
extremities, feet, ear, tail, wattles, comb
What is the gross appearance of dry gangrene?
dry, shriveled, and leathery with a sharp line of demarcation
What causes dry gangrene?
interference of blood supply (ischemia)
List some examples of things that can cause dry gangrene (3):
freezing, vascular constriction, thrombosis
Where does moist gangrene occur?
in tissues that are rich in blood and fluids (lung, intestine, mammary gland, and muscle masses)
What bacterial process is favored in moist gangrene?
digestion of tissues
Describe the appearance of moist gangrene:
appears flabby, swollen, and soft, usually has a strong putrefactive odor, and may be pale, red or blackened
In life, gangrene is:
painless and cool to the touch
Gas gangrene is:
a form a moist gangrene caused by the invasion of gas-producing bacteria of the genus Clostridium
Why specifically Clostridium when dealing with gas gangrene?
have the ability to induce necrosis then live as saprophytes in the dead tissue
Name 2 disease examples where gas gangrene is a prominent feature:
blackleg, malignant edema
Which lymphocyte is present at the borders of gangrenous tissue?
neutrophils
Effects of dry gangrene:
sloughing of the involved portion of the extremity (animal may live)
Effects of moist/gas gangrene:
absorption of toxic materials and bacteria from the putrefaction (sapremia - can lead to fatal toxemia and sepsis)
Once cells die, three dynamic changes occur over the next hours/days:
- calcium salts accumulate
- cholesterol from membranes crystallizes
- phosopholipids from membranes form myelin figures
Gangrene is a follow up process to:
necrosis
Why can freezing lead to necrosis?
excessive vasoconstriction can lead to devitalization/necrosis; ice crystal formation can lead to vascular rupture
Why would there be tan coloration along the line of demarcation for gangrene?
live epidermis is dying, drying out, and lifting away from the dead tissues
The line of demarcation in gangrene denotes:
where the vasoconstriction occured
the degree to which a substance can cause harm
toxicity
the actual disease condition of an animal due to poisoning
toxicosis
Which type of gangrene has no significant effect on the animal’s long term health?
dry gangrene
What is the only real difference between dry and moist gangrene?
relative amount of moisture in the tissue involved
bacteria that feed on dead material - whether from within the body from outside
saprophytic bacteria
a medical condition in which a part of the intestine folds into the section next to it
intussesception
How can intussesception lead to gangrene?
static blood flow leads to hypoxia and eventually to anoxia; cellular degeneration is initiated and eventually progresses to necrosis
Where do saprophytic bacteria in an intussesception come from?
lumen of the intestine
Why are the results of moist gangrene so serious?
toxins from both the breakdown of putrefying tissue and from the bacteria are readily absorbed into the circulation
What can cause a green coloration to tissues (4)?
- eosinophil inflammation
- algae infection
- green jaundice (never really seen)
- sulfhemoglobin
disease caused by feed-borne toxin that damages the type 1 pneumocytes that line alveoli
acute (atypical) interstitial pneumonia
What happens if gastric fluid (hydrochloric acid and pepsin) is accidentally aspirated?
causes tremendous pulmonary damage (necrosis) and open the door bacterial invasion
What happens to cause the green coloration in lungs when gastric acid is aspirated?
anaerobic environment is produced - H2S and hemoglobin combine, forming sulfhemoglobin and bilirubin
On microscopic view, if you can still recognize the general tissue outlines, you might be looking at what type of necrosis?
coagulative
What happens when Fusobacterium necrophorum becomes established in an injured tissue?
creates its own ideal environment for proliferation and causes severe progressive necrosis
Algor mortis
cooling of body after death; highly variable
What are some of the variables of algor mortis?
body temperature at time of death, ambient temperature, fat covering, wool or hair covering, etc.
Rigor mortis
rigidity of skeletal and cardiac muscles after death
Where does rigor mortis begin? Where does it progress to?
anterior muscles first and progresses posteriorly
How long does it take for the beginning stages of rigor mortis to set in?
1-6 hours
How long until rigor mortis disappears and why?
18-24 hours (but may persist for several days); beginning of autolysis
Give the pathologic reasoning for rigor mortis:
due to loss of ATP production by the muscle cells when blood flow stops and all muscle glycogen is exhausted
Why does loss of ATP cause rigor mortis?
actin and myosin of muscles cannot work without it
Liver mortis
postmortem hypostatic congestion
When does liver mortis begin?
within an hour or so after death
When does liver mortis reach its peak?
within a few hours
As postmortem lysis of blood occurs (usually after 10-18 hours), the freed hemoglobin escapes into the adjacent tissues giving them a homogeneous red coloration
hemoglobin imbibition
Autolysis:
softening of tissues due to release of proteolytic enzymes within the cell
List some of the tissues that autolyze faster than others (5):
brain, liver, kidney, lining of GI, adrenal medulla, gall bladder epithelium
The accumulation of gas in the GI tract due to continued fermentation and progressing putrefaction
postmortem bloat
How do you differentiate postmortem bloat from antemortem bloat?
Antemortem bloat has evidence of cyanosis in the cervical and head tissues
Postmortem emphysema
the accumulation of gas in tissues other than the GI tract (caused by saprophytes)
What organs are most commonly involved in postmortem emphysema?
lungs, liver
Postmortem digestion of tissues by bacteria, fungi:
putrefaction
Where are the most common places to see Pseudomelanosis?
GI tract, abdominal viscera
Pseudomelanosis
postmortem blackening of the tissues
H2S (from putrefaction) + Fe (from blood) –>
Fe2S3 (iron sulfide - which is black; pseudomelanosis)
Hemoglobin comining with acid in putrefyng tissues produces:
hematin crystals, an artifact of autolysis
Seeping of bile pigments through the gall bladder and bile duct into adjacent tissues giving them a greenish-yellow hue
bile imbibition
What two imbibition processes occur at about the same rate as each other?
bile, blood
What is the primary difference between autolysis and necrosis?
autolysis is diffuse, necrosis is a focal/multifocal process
Why is evidence of inflammation indicative of necrosis?
because there is a tissue rxn (dead tissues do not exhibit inflammation)
Decomposition of protein under aerobic conditions - utilized as a food source by microbes:
decay
settling of blood to the most ventral portions of the body immediately after death before clotting occurs
liver mortis (hypostatic congestion)
When glycogen and ATP in the myocytes become depleted, the muscle fibers:
remain in a state of sustained contraction (rigor mortis)
What 2 things antemortem can accelerate the onset of rigor?
intense muscular activity, high temperature
The tan foci sometimes left behind by putrefaction (bacterial colonies), can look like what previous module we learned about? How do you tell the difference?
foci of necrosis; histopath
How do we distinguish nuclei in autolysis vs. necrosis?
autolysis - stain weakly and fade out gradually (karyloysis)
necrosis - undergo predictable changes
Saprophytic bacteria can be a feature of (2):
decomposition (dead animal); gangrene (dead tissue in a live animal)
A common change associated with autolysis (micrscopically):
separation of epithelial cells from the lamina propria or submucosa
Very common in sheep:
copper toxicity
What does PAS stain?
glycogen
What is the name for a yellow coloration?
icterus
Tubules of the kidney are lined by:
cuboidal epithelial
Normally, the lumens of the kidney tubules should be:
clear
Why do we use congo red for staining?
taken up by amyloid
What are the ultrastructure features of cell injury (5)?
- detachment of ribosomes from RER
- Formation of “blebs”
- Swelling of mitochondria
- ER dilation
- Cell swelling
What is a critical step in a cell transitioning from reversible to irreversible cell damage?
membrane damage
What is an important mediator of many biochemical and morphologic alterations leading to cell death?
calcium
What would you call a lesion affecting the white matter of the brain?
leukoencephalomalacia
