Post Mortem Investigations (PMI) Flashcards
Why did the animal die? Find out these 3 things..
- Cause of death
- Mechanism of death
- Manner of death
Cause of death
- The disease, injury or abnormality that alone or in combination with other factors is responsible for initiating the sequence of functional disturbances that resulted in live stranding and death.
- During this procedure the following may be further defined:
Immediate cause of death
Underlying cause of death
Contributing factors
Mechanism of death
The immediate physiologic derangement resulting in death.
A particular mechanism of death can be produced by a variety of different causes of death.
Manner of death
How death came about. Distinguish between:
- Natural: natural disease or toxic processes
- Anthropogenic: accidental: e.g. ship strikes, non-accidental: volitional act or direct killing
- Undetermined: inadequate information
Requirements when performing a necropsy in the field
- Cleanable
- Far from healthy and alive animals
- Close to water supply
- Easy to reach with track for carcass disposal
What is virtopsy?
- Virtual autopsy, on frontier of research,
Doesn’t happen very often.
- Use MRI or CT scan
- Reconstruct 3D model
What happens after death?
Heart stops –> no blood flow –> no organ perfusion –> enzymes releases outside the cells –> no oxygenation –> no warmth –> organ failure
What is the difference between individual and biological death?
Individual death: may be reversible, cells and organs stay alive for limited hours after death
Biological death: irreversible. Typically happens after loss of cardiorespiratory or brain function
Agonal period
- interval between the time of fatal injury and death
Supravital reactions
- biological processes that occur in tissues after death or during a state of near-death
Postmortal phase
Consists of 3 processes:
-Autolysis: the destruction of cells or tissues by their own enzymes, especially those released by lysosomes.
- Putrefaction: the process of decay or rotting in a body or other organic matter.
-Decomposition: state or process of rotting
What are the 5 steps of human taphonomy (how organisms decay)?
- Corneal clouding
- Pallor mortis
- Algor mortis
- Livor mortis
- Rigor mortis
Corneal clouding
- Thin film forming.
- Mins after death if eyes open, to > 24 hours if eyes are closed.
Pallor mortis
- First visible change to the body
- 15 to 20 minutes after death
- Body begins to pale. Occurs because blood stops moving through the capillaries
Algor Mortis
- Translated from Latin as “cold death”
- Describes postmortem temperature change after someone has died.
Livor mortis
- Settling of blood in the lowest part of the body due to gravity.
- The blood will start pressing on the skin leaving red/purple marks on the body.
Rigor mortis
- Stiffening of the body muscles due to chemical changes in their myofibrils, specifically a lack of ATP (adenosine triphosphate), which is needed to relax muscles.
Can we use algor mortis for marine mammals?
No, because:
- Blubber layer: After death, this layer continues to insulate the body, significantly slowing the rate of heat loss compared to other animals.
- Postmortem hyperthermia in whales: body temperature can go from 37 up to 70 C because of bacteria composition –> unique to large marine animals because of size and insulation trap heat, preventing it from dissipating as quickly as it would in smaller or less insulated animals
Can we use rigor mortis for marine mammals?
Only limited use.
Unique characteristics e.g. blubber, varying body sizes, and aquatic environment—make process less straightforward and predictable compared to humans. But processes are the same:
- Autolysis: contributes to progression of rigor mortis as muscle cells lose integrity and no longer able to maintain normal chemical gradients.
- Release of Ca2+ from the sarcoplasmic reticulum (a structure within muscle cells that stores calcium) = critical part of rigor mortis. Normally, calcium is kept in check by ATP-driven pumps, but after death, Ca2+ flood the muscle fibers. This influx of calcium causes the muscles to contract, leading to stiffness of rigor mortis.
- In living animals, ATP binds to myosin (a protein in muscle fibers) to release the muscle from its contracted state. After death, when ATP production stops, muscles remain in a contracted state because myosin cannot release from actin (another muscle protein). Leads to stiffness
- Rm peaks 12 hours after death. Muscles reach maximum stiffness. After this peak, rigor mortis gradually dissipates as tissues begin to break down due to decomposition, and muscles lose their structure.
Can we use livor mortis for marine mammals?
Only in few situations.
- Reduced blood clotting in marine mammals helps prevent issues like decompression sickness and allows them to manage blood flow better during dives. So after death, blood in may not clot as quickly or efficiently. Clotted blood is less likely to pool and settle in the same way as in mammals with normal clotting capacity. Less reliable for analysis.
- Amount of hemoglobin in cetaceans is higher than in other mammals.
Can we use pallor mortis for marine mammals?
No, because:
- Blubber difficult to observe pallor or skin color changes. Blubber insulates the body, and the skin often remains intact and unaffected by the loss of blood circulation, making it hard to notice any color change.
- Fur in pinnipeds This fur can obscure any visible signs of pallor. The fur also adds another insulating layer, preventing the visible manifestation of the blood draining from the skin.
- Different skin colour than humans. Many marine mammals have naturally dark or differently pigmented skin compared to humans, which makes the contrast in color less apparent after death.
Is autolysis common in living adult organisms?
Autolytic cell destruction is uncommon in living adult organisms and usually occurs in injured cells and dying tissue
In what type of tissues is autolysis more rapid?
More rapid in glandular tissues with a rapid metabolism (liver, intestine, etc.)
How is autolysis initiated?
Initiated by the cells’ lysosomes releasing digestive enzymes into the cytoplasm.
These enzymes are released due to the cessation (ending) of active processes in the cell, not as an active process
In what post mortem phenomena does autolysis play a role?
o p.m. hemolysis and hemoglobin staining (leukocytic enzymes)
o ocular changes
o tissues destruction
o rigor mortis disappearance
Putrefaction vs fermentation
- Fermentation is a metabolic process where microorganisms, especially yeast and bacteria, convert sugar into acids, gasses and alcohols
- Putrefaction is the decay of organic matter by microorganisms, which results in the formation of compost and a foul smell.
What happens in the body during putrefaction/ fermentation?
Aerobic and anaerobic bacteria multiplicate in decomposed tissues: their enzyme causes putrid (decaying) fermentation with gas production
Where do putrefaction/ fermentation bacteria come from?
- Internal anaerobic bacteria coming from intestine
- Other bacteria coming from the external environment penetrating from orifices or wounds
What are ptomaines?
Organic molecules based on nitrogen formed from putrefaction
Decomposition condition code (DCC) scoring system for cetaceans
- Code 1: extremely fresh carcass, just dead
- Code 2: fresh carcass
- Code 3: moderate decomposition
- Code 4: advanced decomposition
- Code 5: Mummified or skeletal remains
Sea turtle DCC
- Good (fresh carcass)
- Minimal decomposition
- Decomposition
- Mummified or skeletal remains
Sea turtle DCC with description
Which analysis for each DCC? (important)
Which analysis for each DCC? (important)
Which analysis for each DCC? (important)
What findings are important to describe during a necropsy?
Morphological differences C. caretta, D. coriacea and C. mydas
What do the arrows indicate?
Umbilicus (navel)
What do the arrows indicate?
Anus
What do the arrows indicate?
Genital slit
What do the arrows indicate?
Mammary slits
How to identify a calf?
▪ Foetal folds/neonatal plicae
▪ Whiskers (vibrissae) used to perceive the mother
▪ Lateral papillae (see pic)
▪ Unerupted teet
What do we see here and how can we determine its a calf or adult?
-Kidney filtering unit, glomerulus
- Kidneys new born: cells present as in the picture
- Adult: cells migrate internally
What do we see here?
In picture: gonads nearly ready for
reproduction, so adult or juvenile
Sexual maturity means presence and stage of gonads
Incremental Growth Layers (IGLs) as method to determine age
Parallel layers of hard tissue (dentine, bone, or cementum) that form as organism grows.
These layers contrast with adjacent layers due to differences in their appearance or composition, and can be observed using different techniques:
Opacity/Transparency with Transmitted Light: When light is shone through a thin section of a tooth or bone, the layers can appear more or less transparent.
White/Dark Layers with Reflected Light
Acid Treatment
Higher/Lower Intensity of Color Using Decalcification and Cutting
Growth Layer Groups (GLGs) as method to estimate age
GLGs refer to groups of Incremental Growth Layers that form in regular cycles and reflect an organism’s growth over time.
Each group represents specific period in animal’s life, usually corresponding to one year:
- Change of Main Features: corresponds to annual event like change of season
- 1 GLG = 1 year of growth
Give age estimations
What is the arrow indicating?
Pulp cavity
(T. truncatus)
5 stages of Nutritional Condition Code (NCC)
What is stable isotope analysis? What do we use it for?
- Same number of protons and unequal number of electrons
- Stable isotopes (vs radioactive) have stable nucleus remaining over time
- Stable Isotopes are present everywhere in the world in which we live and breathe but:
- Balance (or ratios) in which different isotopes of the same elements occur,
varies between different substances (eg different types of food) and ecosystems (eg between land and sea or between different climate zones) - The ratios of different isotopes in different tissues and using scientific knowledge about how they occur in nature measure their diet and environment in time
Which istope ratios are used to analyze diet and which ones for migration?
DIET:
- carbon: 13C (or C-13) and 12 C (or C-12). The ratio between the two ( 13C/12C) is referred to as δ13 C (pronounced: delta-13-C) values
- nitrogen: 15N (or N-15) and 14 N (or N-14). Ratio between the two (15N/14N) is given as δ15N (delta-15-N) values
MIGRATION:
- oxygen: 18O (O-18) and 16 O (O-16), with ratio ( 18O/16O) referred to as δ18O (delta-18-O) values
- strontium: 87Sr (Sr-87) and 86 Sr (Sr-86). Strontium isotope ratios are referred to as 87Sr/86Sr ratios
What are the turnover rates of the different tissues?
- Days to weeks: blood plasma and liver
- Months: muscle, blood cells, skin and
blubber - Years: bones
- Lifetime (no turnover): e.g. teeth, earplugs, baleen
Example: skin layers of dolphins change every 3 months, the dermal one remains for more time. Comparing them we can understand if there were changes in diet in the last 3 months
How to collect and preserve the different tissues and prepare the samples. (Table)
Skin anatomy
-Absence of hairs (except for vibrissae) and other adnexa
- Epidermis: no distinction between stratum granulosum and stratum lucidum
- Epidermis: 15-20 times thicker than human skin, with a rapid turnover
- Epidermis: lipokeratinocytes (95%) and melanocytes more represented cells
- 70 – 80 percent of epithelial cells turnover really quickly, 3 months to be entirely changed.
- White layer: epidermal layer
Black layer: epithelial layer
What to do in case of stranding
A: Summer
B: Winter
Cyamidae (crustacea, Amphipoda)
“Whale lyces”
Life cycle of Ozobranchus (Marine leeches)
Chelonibia testudinaria (Barnacles)
Balanids
