Week 4 is almost to a close, I am busy reading about thermoregulation in marine mammals (Andersen) and reviewing the proper necropsy procedures for the nervous/reproductive system.
Females: By following the reproductive tract from the vagina up, the ovaries, fallopian tubes and uterus can be found. The uterus will be a tan-pinkish color and depending on the sexual maturity of the specimen, can vary in size and thickness. Reproductive history and trauma may also alter the appearance of the uterus. Examine the internal and external surfaces, noting all the usual characteristics (by now you should know, Danny). Pregnant females will contain a fetus that can also be necropsied if it is large enough. If the fetus is of sufficient size to be examined, incise the abdomen and extract lung tissue, performing the same floating test as was done for adult tests. If the lung tissue floats in water, bronchiole expansion of the lungs has occurred. If the fetus is too small to necropsy, preserve it in formalin.
The left and right ovaries are attached to the end of each respective uterine horn and will appear as off-white and spindle shaped. Detach them to further inspect. Corpus albicans will be present on mature ovaries, while corpus luteum will be present on a pregnant female's ovaries. Weight and measure each ovary and count the number of scars. Examine internally.
Males: The testes are also spindle shaped and off-white and are located outside of the abdominal cavity along the ventral body wall and proximal to the ventral hip bones. This is evolutionarily advantageous as sperm production is often a function of temperature, and regulating temperature is easier away from the variable heat-producing viscera of the abdominal cavity. Remove the testes and weigh/measure them, examining both the organ itself and the epididymus inside and out. Check for the presence or absence of sperm in the epididymus and obtain a sample if possible.
The last part of the necropsy is also the most delicate, as it involves a fragile and extremely important organ: the brain. A lot of the techniques described in WHOI's guide are meant for seasoned necropsiers, so I also doubt I will take the lead on hack-sawing the skull, but detailing the process is still necessary. I will quote the more detailed parts of this procedure.
The first step to removing the brain is to detach the head from the body. This is accomplished by cutting behind the base of the skull between the first vertebra and the occipital condyles (facets of the occipital bone, the major lower pentagonal bone of the cranium). To help this separation, pull the muzzle towards the ventrum (middle of the body). Once detached, the excess integument can be trimmed away from around the caudal and dorsal sides of the skull. "Then, using a Stryker saw or a hack-saw, make cuts from left to right through the middle of each occipital condyle, then up along the left and right lateral skull, and then across the dorsum, just caudal to the marked transverse ridge at the apex of the skull." Then carefully position a chisel between the pentagon-shaped cut and turn it to crack the remaining bone until the dorsal cranium breaks off. Pull this section off evenly, without using one edge as a lever, to prevent bone from entering the brain tissue. Using your fingers, try to remove the meninges (membranes that protect the nervous system) away from the skull and go around the brain severing cranial nerves. The now-disconnected brain should fall into your hand once inverted.
At this point, handling should proceed gingerly, as the brain is at risk of falling apart. Note symmetry of the brain's structure, look for parasites and record color and texture. Separate the brain into two hemispheres by cutting cranially to caudally. The distinct sections of the brain have their own patterns; the cerebrum has two separate lobes and is the forward-most part of the brain. The cerebellum is the most caudal portion, and the brain stem starts from the ventral midline and then extends down to the spinal cord. The pituitary gland can then be located back on the carcass, and is found under the crossover of the optic nerve. Incise the overlying dura (outermost layer of the meninges) and find the bony recess that is the pituitary gland.
And there you have it! Next week, with Sean Todd back from England, and Jackie Bort and Amanda Dunn to help out, we will hopefully remove one of the seals from Allied Whale's freezer and perform a necropsy. I expect small cetacean necropsies to go along somewhat like the pinniped's, and so there will be less of a detailed description for the porpoises and more emphasis on comparative anatomy/specialized systems/miscellaneous topics. I have isolated the nervous system as another area where I could use more review and so I will consult Andersen and other library sources. After all, this is the first time I heard the terms dura and meninges (although I now understand where the meningitis gets its name). Until next time, ciao.
Friday, January 29, 2010
Thursday, January 28, 2010
Pinniped Necropsy: Abdominal Cavity
As noted earlier, the diaphragm separates the thoracic cavity from the abdomen. By now, both cavities will have been opened, and the dissection should proceed with the removal of the liver. The liver is multi-lobular and maroon. Located over the stomach, the liver is fairly large in pinnipeds, encompassing the majority of the abdominal cavity. The liver should be removed before the gall bladder is incised to prevent contamination, and the parenchyma can be examined by bread-slicing (this technique will come in handy for viewing the inside of most organs). Examine the color pattern and texture of the lobes and parenchyma, all the while searching for parasites (especially in bile ducts).
The gall bladder is a round and green organ that is located ventrally between the right and central lobes of the liver. The gall bladder is a thin walled sac that stores and secretes bile. By cutting into the duodenum (first part of the small intestines), it can be determined whether or not the gall bladder is secreting bile. Check for gall stones. The spleen is a slightly discoid, but mostly oblong purple-white organ found underneath the stomach along the left body wall. Pinniped spleens may be serrated or have irregular margins, a normal sight. Examine the organ and bread-slice. The pancreas is located in the curve of the duodenum and is a lobulated, peach-colored tissue. Look for changes in color in the parenchyma and examine the ducts for parasites. Furthermore, the pancreas is attached to the mesentery, a translucent, malleable but firm connective tissue that is in turn attached to the intestines. Examine the mesentery for any adhesions, and note if there is congestion of the vessels. Lymphatic vessels may be distended with a milk-like fluid if the seal has recently eaten. The mesenteric lymph node can be found centrally on the mesentry and is a large, finger-like lymph node that tends to have a more pronounced cortex and medulla than previously described lymph nodes. As is usual, note any changes in the interior (by cross-section cutting) and exterior aspects of this lymph node.
Next, locate the right and left adrenal glands in situ, as they may be hard to find without the kidney as a guide. These two glands are located anterior to the cranial pole of each kidney, and are small, maroon tissues with irregular furrows over their surface. Pull the tissue distally and cut connecting tissue to remove the adrenal glands. Measure and weigh each adrenal gland and then cut them in half. The medulla should be distinctly darkened, with a lighter cortex. Look for the aperture of the medulla. A normal, pen-tip sized opening indicates usage of the glands. The kidneys are a darker shade of maroon and are reniculated (possessing miniature kidneys). They are attached to the caudal dorsal abdominal wall and are enclosed by the capsule, a connective tissue. Longitudinally incise the capsule and reflect each half to reveal each kidney. Detach them from the abdominal wall and examine the internal and external structure, making note of any stones. also observe the medulla:cortex ratio and the degree of differentiation between the two. Normal reniculi are clearly demarcated and clustered together within the kidney.
The bladder is a relatively small, light pink and found anterior to the pelvic bone along the ventral body wall. If urine is present in the bladder, it may appear thin and slightly translucent, as opposed to a thick-walled appearance when not full. Extract urine aseptically from the bladder, noting the amount, color and consistency, and then remove the bladder. Cut along the length of the organ to expose the mucosal surface and note the color of this mucous.
In past necropsies, most notably the harp seal (P. groenlandica), the stomach held the greatest clues for cause of death, and so special care must be taken to ensure that the stomach is thoroughly analyzed. Tie off both ends of the stomach with twine before removal, one knot at esophagus-stomach interface, the other just below the duodenum. Cut beyond both knots and then examine the serosal (external) surface of the stomach, noting any lesions, or changes in color. If there is a pathological condition, the perigastric lymph node may be enlargened. Incise along the wall with the greatest curvature, and note the stomach contents. These contents can range from food, to fluid, parasites, or even foreign objects. Collect a sample and then run the contents through a sieve to collect solid materials that may have gone unnoticied. Photograph any foreign objects and save them. Now empty, the stomach lining can be examined. Note the mucosa and look for ulcers, parasites and lesions. Weigh the stomach when it is emptied.
The intestines are the last of the abdominal cavity organs to be examined so that they do not contaminate the body. The small intestines should be serosally examined, areas of hemmoraghing or discoloration noted. The inside can be examined by spot checking: select 5-10 random areas and then cut down 10 centimeters of their length, noting color, contents, thickness etc. The large intestines are located by finding the ileo-ceco-colic junction, which is a ridged section between the small-diameter small intestines and the large intestines. Repeat spot checking for both the large intestine and the colon. A sample of feces should be taken from the colon for toxicology analysis.
The last topic to tackle in Pinnipeds is the nervous and reproductive systems. As the endocrine system is spread out all over the body, the relevant glands associated with these systems will be covered, too. Pituitary gland, my eye is on you.
The gall bladder is a round and green organ that is located ventrally between the right and central lobes of the liver. The gall bladder is a thin walled sac that stores and secretes bile. By cutting into the duodenum (first part of the small intestines), it can be determined whether or not the gall bladder is secreting bile. Check for gall stones. The spleen is a slightly discoid, but mostly oblong purple-white organ found underneath the stomach along the left body wall. Pinniped spleens may be serrated or have irregular margins, a normal sight. Examine the organ and bread-slice. The pancreas is located in the curve of the duodenum and is a lobulated, peach-colored tissue. Look for changes in color in the parenchyma and examine the ducts for parasites. Furthermore, the pancreas is attached to the mesentery, a translucent, malleable but firm connective tissue that is in turn attached to the intestines. Examine the mesentery for any adhesions, and note if there is congestion of the vessels. Lymphatic vessels may be distended with a milk-like fluid if the seal has recently eaten. The mesenteric lymph node can be found centrally on the mesentry and is a large, finger-like lymph node that tends to have a more pronounced cortex and medulla than previously described lymph nodes. As is usual, note any changes in the interior (by cross-section cutting) and exterior aspects of this lymph node.
Next, locate the right and left adrenal glands in situ, as they may be hard to find without the kidney as a guide. These two glands are located anterior to the cranial pole of each kidney, and are small, maroon tissues with irregular furrows over their surface. Pull the tissue distally and cut connecting tissue to remove the adrenal glands. Measure and weigh each adrenal gland and then cut them in half. The medulla should be distinctly darkened, with a lighter cortex. Look for the aperture of the medulla. A normal, pen-tip sized opening indicates usage of the glands. The kidneys are a darker shade of maroon and are reniculated (possessing miniature kidneys). They are attached to the caudal dorsal abdominal wall and are enclosed by the capsule, a connective tissue. Longitudinally incise the capsule and reflect each half to reveal each kidney. Detach them from the abdominal wall and examine the internal and external structure, making note of any stones. also observe the medulla:cortex ratio and the degree of differentiation between the two. Normal reniculi are clearly demarcated and clustered together within the kidney.
The bladder is a relatively small, light pink and found anterior to the pelvic bone along the ventral body wall. If urine is present in the bladder, it may appear thin and slightly translucent, as opposed to a thick-walled appearance when not full. Extract urine aseptically from the bladder, noting the amount, color and consistency, and then remove the bladder. Cut along the length of the organ to expose the mucosal surface and note the color of this mucous.
In past necropsies, most notably the harp seal (P. groenlandica), the stomach held the greatest clues for cause of death, and so special care must be taken to ensure that the stomach is thoroughly analyzed. Tie off both ends of the stomach with twine before removal, one knot at esophagus-stomach interface, the other just below the duodenum. Cut beyond both knots and then examine the serosal (external) surface of the stomach, noting any lesions, or changes in color. If there is a pathological condition, the perigastric lymph node may be enlargened. Incise along the wall with the greatest curvature, and note the stomach contents. These contents can range from food, to fluid, parasites, or even foreign objects. Collect a sample and then run the contents through a sieve to collect solid materials that may have gone unnoticied. Photograph any foreign objects and save them. Now empty, the stomach lining can be examined. Note the mucosa and look for ulcers, parasites and lesions. Weigh the stomach when it is emptied.
The intestines are the last of the abdominal cavity organs to be examined so that they do not contaminate the body. The small intestines should be serosally examined, areas of hemmoraghing or discoloration noted. The inside can be examined by spot checking: select 5-10 random areas and then cut down 10 centimeters of their length, noting color, contents, thickness etc. The large intestines are located by finding the ileo-ceco-colic junction, which is a ridged section between the small-diameter small intestines and the large intestines. Repeat spot checking for both the large intestine and the colon. A sample of feces should be taken from the colon for toxicology analysis.
The last topic to tackle in Pinnipeds is the nervous and reproductive systems. As the endocrine system is spread out all over the body, the relevant glands associated with these systems will be covered, too. Pituitary gland, my eye is on you.
Monday, January 25, 2010
Cardiovascular Adaptations
Perusing the how-to necropsy guides has been an indispensable use of study time, but to keep learning fresh and to gain further insight into marine mammal anatomy I have started to consult other books. Andersen, H.T. (1969) The biology of marine mammals., has proved a very concise and intriguing source, and lists separate anatomical subjects in chapters. As I was covering the cardial tissues last, I skipped to the corresponding section in Andersen regarding cardiovascular adaptations to diving. Much of this chapter seemed to be review, as I have covered diving adaptations in previous classes (Sperm Whale Diving Adaptations, Marine Mammal Biology I; The Weddell Seal, Polar Ecology and Exploration), but I did appreciate Andersen's inclusion of the history of diving adaptation discovery in marine mammals, and his comparisons to terrestrial mammals. I was less grateful for all the descriptions of forcibly submerging and drowning mammals, but who has time to delve into ethical attitudes of the 1960's.
I won't repeat the cardiovascular adaptations here, as my previous papers do a fairly good job of explaining the profound ability of cetaceans and pinnipeds to dive, but I think it is worthy to note several insights the chapter provided. Vasoconstriction is a critical requirement of marathon diving, whereby bloodflow slows and even halts in the peripheral and distal vessels. This lessens the overall oxygen demand, maintaining high levels of oxygen in the organs and tissues most vital to survival and feeding (esophagus, brain, heart). Much of the skeletal muscle, too, is deprived of oxygenated blood during these long dives. While this may seem counterintuitive, as the animal needs to be able to use its muscles to swim, it makes perfect sense in practice. Myoglobin is highly concentrated in muscle tissue and has a higher affinity for oxygen than haemoglobin. If blood flow were not slowed past these muscles, the myoglobin would rob the blood of its oxygen, preventing it from traveling to the aforementioned vital organs. Marine mammals have an incredible tolerance to high blood pH and lactic acid buildup, so their muscles can still operate under anaerobic conditions for the duration of the dive.
What really struck me was how tight this separation between peripheral vessels and muscle was from the main bloodflow. Lactic acid levels were shown to remain at steady levels during the dive, but dramatically rose once the animal had surfaced, before gradually tapering off again. This clearly illustrates the ability of marine mammals to separate parts of their body that are anaerobically respirating from the parts that are reliant on oxygen.
Harrison, R.J. (1971) Functional Anatomy of Marine Mammals., is another source I consulted, but after browsing its chapters, it was clear that Harrison tackles mostly advanced and specialized topics on select marine mammals. This book will come in handy when a certain species requires additional attention, but as a day-to-day guide, there are better options such as Andersen and Dierauf. Speaking of Dierauf, I found a free Internet copy of the Pinniped Forensic, Necropsy and Tissue Collection Guide.
I won't repeat the cardiovascular adaptations here, as my previous papers do a fairly good job of explaining the profound ability of cetaceans and pinnipeds to dive, but I think it is worthy to note several insights the chapter provided. Vasoconstriction is a critical requirement of marathon diving, whereby bloodflow slows and even halts in the peripheral and distal vessels. This lessens the overall oxygen demand, maintaining high levels of oxygen in the organs and tissues most vital to survival and feeding (esophagus, brain, heart). Much of the skeletal muscle, too, is deprived of oxygenated blood during these long dives. While this may seem counterintuitive, as the animal needs to be able to use its muscles to swim, it makes perfect sense in practice. Myoglobin is highly concentrated in muscle tissue and has a higher affinity for oxygen than haemoglobin. If blood flow were not slowed past these muscles, the myoglobin would rob the blood of its oxygen, preventing it from traveling to the aforementioned vital organs. Marine mammals have an incredible tolerance to high blood pH and lactic acid buildup, so their muscles can still operate under anaerobic conditions for the duration of the dive.
What really struck me was how tight this separation between peripheral vessels and muscle was from the main bloodflow. Lactic acid levels were shown to remain at steady levels during the dive, but dramatically rose once the animal had surfaced, before gradually tapering off again. This clearly illustrates the ability of marine mammals to separate parts of their body that are anaerobically respirating from the parts that are reliant on oxygen.
Harrison, R.J. (1971) Functional Anatomy of Marine Mammals., is another source I consulted, but after browsing its chapters, it was clear that Harrison tackles mostly advanced and specialized topics on select marine mammals. This book will come in handy when a certain species requires additional attention, but as a day-to-day guide, there are better options such as Andersen and Dierauf. Speaking of Dierauf, I found a free Internet copy of the Pinniped Forensic, Necropsy and Tissue Collection Guide.
Sunday, January 24, 2010
The Pinniped's Heart
By now we have observed all of the organs of the pluck except one: the heart. The pericardium is the sac that contains the heart, and this should be trimmed away to see the epicardium (external surface of the heart). A small amount of clear fluid is contained within the pericardium, which allows for lubrication during normal heartbeat activity. If there is a lot this fluid (pericardial effusion), and if it is off-colored, make a note of it as this may indicate a wide variety of cardial issues such as pericarditis (inflammation of the pericardium), complications from tuberculosis, trauma, etc.
The mammalian heart is separated into 2 ventricles and 2 atria. Deoxygenated blood flows from the ventricles directly into the right atrium, where the tricuspid valve then shuttles it into the right ventricle. The pulmonary valve shuttles this blood into the pulmonary artery, which passes by the lungs. Oxygenated blood then travels from the pulmonary vein into the left atrium where the mitral valve is, and then this blood is sent into the left ventricle, then through the aortic valve and into the arteries and aorta where it is sent throughout the body. All of the valves, ventricles, atria and the aorta and pulmonary valve should be examined and noted for any inconsistencies during the necropsy. This can be accomplished by removing the heart from the aorta and pulmonary artery by cutting the two transversely, leaving 6 centimeters of each vessel still attached. To examine the internal structures, two methods can be utilized:
Using scissors, make a small incision in the right atrium and cut along the peripheral edge going towards the apex (lowest part of the heart), then following up the right ventricle side of the septum until you reach the pulmonary artery. Then cut the left ventricle side of the apex, go along the septum until the aorta is reached. This leaves both sides of the heart intact, but is fairly complicated. A simpler way is to slice the entire organ in half starting from the apex and then travelling laterally towards the vessels.
The pulmonary artery is a flappy vessel that enters the right atrium cranially while the aorta is the most muscular and tough artery. Both should be cut longitudally and examined for defects. The left atrium and ventricle should have thicker and more muscular walls than the right side (thickness ratio of around 2:1), with the left ventricle the thickest part of the heart. The right pulmonary vein and right atrium are the most flaccid. Unusual structures within the chambers of the heart may suggest hereditary illness or vestigal fetal structures. They, along with lesions should be recorded. The myocardium can be examined by bread-slicing the ventricles.
And that was the heart! While I was initially intimidated by the intricacies of the heart's anatomy, it was more straightforward than I thought it would be. Next entry will explore the abdominal cavity. Then the pinniped part of this study will be complete and we can move on to small cetaceans.
The mammalian heart is separated into 2 ventricles and 2 atria. Deoxygenated blood flows from the ventricles directly into the right atrium, where the tricuspid valve then shuttles it into the right ventricle. The pulmonary valve shuttles this blood into the pulmonary artery, which passes by the lungs. Oxygenated blood then travels from the pulmonary vein into the left atrium where the mitral valve is, and then this blood is sent into the left ventricle, then through the aortic valve and into the arteries and aorta where it is sent throughout the body. All of the valves, ventricles, atria and the aorta and pulmonary valve should be examined and noted for any inconsistencies during the necropsy. This can be accomplished by removing the heart from the aorta and pulmonary artery by cutting the two transversely, leaving 6 centimeters of each vessel still attached. To examine the internal structures, two methods can be utilized:
Using scissors, make a small incision in the right atrium and cut along the peripheral edge going towards the apex (lowest part of the heart), then following up the right ventricle side of the septum until you reach the pulmonary artery. Then cut the left ventricle side of the apex, go along the septum until the aorta is reached. This leaves both sides of the heart intact, but is fairly complicated. A simpler way is to slice the entire organ in half starting from the apex and then travelling laterally towards the vessels.
The pulmonary artery is a flappy vessel that enters the right atrium cranially while the aorta is the most muscular and tough artery. Both should be cut longitudally and examined for defects. The left atrium and ventricle should have thicker and more muscular walls than the right side (thickness ratio of around 2:1), with the left ventricle the thickest part of the heart. The right pulmonary vein and right atrium are the most flaccid. Unusual structures within the chambers of the heart may suggest hereditary illness or vestigal fetal structures. They, along with lesions should be recorded. The myocardium can be examined by bread-slicing the ventricles.
And that was the heart! While I was initially intimidated by the intricacies of the heart's anatomy, it was more straightforward than I thought it would be. Next entry will explore the abdominal cavity. Then the pinniped part of this study will be complete and we can move on to small cetaceans.
Thursday, January 21, 2010
Inner Organs: Thoracic Cavity
In my previous post, I accidentally omitted the procedure for removing the rib cage. In order to reach the tracheobronchial lymph node, and the other organs of the thoracic cavity, this step is necessary. The abdominal organs are first exposed by making an incision on the abdominal wall mid-ventrally at the site of the last rib. Cutting cranially along the thoracic arch, reflect the abdominal musculature as you go along. The thoracic cavity is then opened by trimming away muscle attached to the rib and deflating the diaphragm by puncturing it. Note if there is deflation, as an absence of deflation can suggest severe pneumonia. It is important to note that the diaphragm is a large structure that separates the thoracic cavity from the abdominal cavity, and once punctured, will deflate healthy lungs due to positive ambient air pressure invading a previously air-proof cavity. The rib cage is then removed by cutting through each thoracic rib mid-articulation (also known as a sweet spot). This is a flex point made of cartilage whose purpose is to allow movement during breathing. Cutting cranally, the ribs should also be reflected, revealing the thoracic cavity.
Pinnipeds have comparatively larger thoracic cavities than their terrestrial distant relatives. This was especially apparent during my last necropsy on a gray seal (Halichoerus grypus), as that specimen's neck was almost as long as the rest of its body. This is congruent with the seal's opportunistic diet, as it must be able to seize any size of fish possible. The esophagus found in pinnipeds has the attributes of extreme flexibility and elongation, a necessity to process large prey.
Organs in the thoracic cavity can be removed and examined separately, or be removed together. The latter situation involves removing the tongue, larynx, trachea, esophagus, bronchi, lungs and heart and is termed the pluck. This procedure enters through the head, as skin is peeled off the chin and neck and then the sides of the mouth are cut open, the incisions extended caudally to the thorax. While pulling the tongue, the connective tissue and muscle holding the pluck is snipped until everything falls
loose. I witnessed this on my first necropsy of a harp seal (Phoca groenlandica) and it was performed by a veterinarian. Thus it is my guess that until a vast amount of practical experience is accrued, I will not attempt this particular method. Maybe someone will prove me wrong..
As noted before, healthy lungs may collapse when the diagraphm is deflated. These organs are large and conspicous in the thoracic cavity, and will normally have a bright pink color and sponge-like texture. The lungs can be detached at the bifurcation of the trachea and then examined. Pressing down on the lungs, gauge if they bounce back, as normal lung tissue will act sponge-like. Additionally, healthy lungs should float if placed in water or a formalin solution. Translucent connective tissue connects lobules in pinniped lungs, and this tissue can become filled with gas in a pathological condition known as emphysematous. Using scissors, cut along the bronchioles of each lung and note if there are parasites, fluid, etc. Next, by bread-slicing you can further eamine the tissue. Make parallel slices perpendicular to the long axis of the body, and is best accomplished by a swift and single cut. This will allow you to view the bulk of the organ (parenchyma) and note any deviations from normal color/texture without any tears or serrations. The trachea should also be examined by cutting longitudinally along the entire length and then examining any mucus or other fluids.
My next post will deal with the heart. I am consulting further texts beyond the necropsy guides to further my knowledge of the heart because I honestly don't have a full grasp of the mammalian heart. Until then, ciao.
Pinnipeds have comparatively larger thoracic cavities than their terrestrial distant relatives. This was especially apparent during my last necropsy on a gray seal (Halichoerus grypus), as that specimen's neck was almost as long as the rest of its body. This is congruent with the seal's opportunistic diet, as it must be able to seize any size of fish possible. The esophagus found in pinnipeds has the attributes of extreme flexibility and elongation, a necessity to process large prey.
Organs in the thoracic cavity can be removed and examined separately, or be removed together. The latter situation involves removing the tongue, larynx, trachea, esophagus, bronchi, lungs and heart and is termed the pluck. This procedure enters through the head, as skin is peeled off the chin and neck and then the sides of the mouth are cut open, the incisions extended caudally to the thorax. While pulling the tongue, the connective tissue and muscle holding the pluck is snipped until everything falls
loose. I witnessed this on my first necropsy of a harp seal (Phoca groenlandica) and it was performed by a veterinarian. Thus it is my guess that until a vast amount of practical experience is accrued, I will not attempt this particular method. Maybe someone will prove me wrong..As noted before, healthy lungs may collapse when the diagraphm is deflated. These organs are large and conspicous in the thoracic cavity, and will normally have a bright pink color and sponge-like texture. The lungs can be detached at the bifurcation of the trachea and then examined. Pressing down on the lungs, gauge if they bounce back, as normal lung tissue will act sponge-like. Additionally, healthy lungs should float if placed in water or a formalin solution. Translucent connective tissue connects lobules in pinniped lungs, and this tissue can become filled with gas in a pathological condition known as emphysematous. Using scissors, cut along the bronchioles of each lung and note if there are parasites, fluid, etc. Next, by bread-slicing you can further eamine the tissue. Make parallel slices perpendicular to the long axis of the body, and is best accomplished by a swift and single cut. This will allow you to view the bulk of the organ (parenchyma) and note any deviations from normal color/texture without any tears or serrations. The trachea should also be examined by cutting longitudinally along the entire length and then examining any mucus or other fluids.
My next post will deal with the heart. I am consulting further texts beyond the necropsy guides to further my knowledge of the heart because I honestly don't have a full grasp of the mammalian heart. Until then, ciao.
Sunday, January 17, 2010
Internal Examination: Lymph Nodes
With the external layers now peeled off and disposed of, the inner cavity of the body and its organs can be examined. Pinniped Forensic Necropsy and Tissue Collection Guide (Dierauf, L.A. 1994) arranges the abdominal cavity inspection directly after blubber and excess muscle are removed. Woods Hole Oceanographic Institution's guide (Pugliares, et al. 2007) recommends an examination of several glands before the body cavity is opened. This order is congruent with that of previous necropsies I have attended and is thus the mostly likely procedure I will encounter while at COA, and since the WHOI's guide is more recent, it likely represents the most current and agreed upon necropsy technique.
Prescapular lymph node: To access the prescapular lymph node, the front flippers will need to be removed. With the subject ventral side up, pull the flipper away from the body and cut through the connective tissue all the while searching for the prescapular lymph node. This lymphatic organ is normally oval, beige or peach colored and firm. Deviations from this template may indictate disease or dysfunction, and should be recorded. The cortex (outer layer) and medulla (center of lymph node) may differ slightly in coloration. This is normal.
Thyroid: The paired thyroids can be found along the lateral sides of the cranial trachea and are distinguished by their dark purple color and flat and disk-like shape. The texture should feel like smooth muscle (for a comparison, feel the stomach or esophagus). As these glands are among the most important in the endocrinal system, any abnormalities should be noted. The parathyroid can also be isolated and sampled. This light colored tissue will be located on the cranial side of the thyroid and is important in regulating calcium.
Thymus: This organ can be found mainly in neonates, although some juveniles and adults have vestigal remnants. The thymus is absorbed after weaning and thus will be difficult to find in adult individuals. If a young of the year or neonate is the subject of the necropsy, however, the thymus can be located at the base of the thoracic inlet (superior thoracic aperture), bordering the cranial side of the heart. (Fun note: Sweetbreads are actually just the thymus of butchered livestock. Gross.)
Although there are other glands (tracheobronchial lymph node, mesenteric lymph node) they will be described alongside the organs they accompany in the body-cavity examination. With the rib cage now exposed, the next step will be to, like the blubber, reflect the ribs away to examine the lungs, heart and other viscera.
Prescapular lymph node: To access the prescapular lymph node, the front flippers will need to be removed. With the subject ventral side up, pull the flipper away from the body and cut through the connective tissue all the while searching for the prescapular lymph node. This lymphatic organ is normally oval, beige or peach colored and firm. Deviations from this template may indictate disease or dysfunction, and should be recorded. The cortex (outer layer) and medulla (center of lymph node) may differ slightly in coloration. This is normal.
Thyroid: The paired thyroids can be found along the lateral sides of the cranial trachea and are distinguished by their dark purple color and flat and disk-like shape. The texture should feel like smooth muscle (for a comparison, feel the stomach or esophagus). As these glands are among the most important in the endocrinal system, any abnormalities should be noted. The parathyroid can also be isolated and sampled. This light colored tissue will be located on the cranial side of the thyroid and is important in regulating calcium.
Thymus: This organ can be found mainly in neonates, although some juveniles and adults have vestigal remnants. The thymus is absorbed after weaning and thus will be difficult to find in adult individuals. If a young of the year or neonate is the subject of the necropsy, however, the thymus can be located at the base of the thoracic inlet (superior thoracic aperture), bordering the cranial side of the heart. (Fun note: Sweetbreads are actually just the thymus of butchered livestock. Gross.)
Although there are other glands (tracheobronchial lymph node, mesenteric lymph node) they will be described alongside the organs they accompany in the body-cavity examination. With the rib cage now exposed, the next step will be to, like the blubber, reflect the ribs away to examine the lungs, heart and other viscera.
Thursday, January 14, 2010
Removing External Layers
To begin the internal examination, the blubber, skin and muscle of the seal must be removed. In some otariids such as the Antarctic fur seal (Arctocephalus gazella) blubber thickness will be reduced, while pelage may be sparse on others such as odobenids. Placing the animal ventral side up, slide a scalpel from under the chin continuing down the midline to the anus, making sure the cut incises down to the muscle-blubber interface. To avoid the penile opening in males, course slightly left. From the midline incision, make perpendicular cuts 15 centimeters apart down the entire length of the animal. Using a hooker, hook on to the panels of flesh and pull distally. A scalpel can then be use this tension to reflect the flensed blubber away from the body.
During the blubber removal, special care should be made not to penetrate or pucture the skeletal muscle or the body cavity that lies underneath. Note any inconsistencies between the preliminary blubber thickness measurements and what is seen during the blubber reflection process. Also record texture and color of the blubber layer. If there are parasites, lesions, bruising or anything other than creamy white to light pink and firm blubber, it too should be noted. The panels of blubber should then be removed and skeletal muscle then examined. Any abnormalities of the muscle mass or fascia should be recorded as excess muscle is trimmed away from the rib cage.
During the blubber removal, special care should be made not to penetrate or pucture the skeletal muscle or the body cavity that lies underneath. Note any inconsistencies between the preliminary blubber thickness measurements and what is seen during the blubber reflection process. Also record texture and color of the blubber layer. If there are parasites, lesions, bruising or anything other than creamy white to light pink and firm blubber, it too should be noted. The panels of blubber should then be removed and skeletal muscle then examined. Any abnormalities of the muscle mass or fascia should be recorded as excess muscle is trimmed away from the rib cage.
Wednesday, January 13, 2010
Pinniped Morphologic Assessment: Pre-Necropsy
With the ice seal stranding season currently underway, knowledge of how to properly necropsy pinnipeds is of primary importance and thus will be my foyer into functional anatomy. Referencing Pugliaries as was done in the first entry, I began on external examinations. Since otariids are not found in the North Atlantic, this entire entry will apply only to phocids, as there are morphological differences that cannot be generalized to both families.
Assessing the condition of a pinniped carcass is a necessary pre-necropsy step, as this can dictate which tests can be done. For example, bacterial tests may only be done on fresh carcasses due to a high probability of contamination in moderately or heavily decomposed specimens. There are five code categories that a stranded seal may fall under:
Code 1: Alive.
Code 2: Fresh carcass
Code 3: Moderate decomposition
Code 4: Advanced decomposition
Code 5: Mummified or skeletal remains
Distinct morphological changes accompany each respective stage, such as bloating evident in moderate decomposing individuals. This can be exhibited by a protruding penis or tongue, and is further differentiated from a fresh carcass by dry mucous membranes, cracked skin and a mild odor. Advancedly decomposed specimens may be found intact, but are severely collapsed, have liquefied internal organs and emit strong odors. Scavenger damage is also often apparent. Mummified or skeletal remains are self-explanatory.
Nutritional Condition: By observing the neck and pelvic regions of a stranded pinniped (deceased or alive), a general assumption about that animal's nutritional condition can be made. This spectrum can range from robust to thin to emaciated. Emaciated individuals exhibit conspicious ribs, protruding pelvic bones and have a visible neck. A healthy, robust individual will appear rounded and have a fusiform body shape. In thin animals, the neck and pelvic bones will show slightly. Blubber thickness measurements will further elucidate any nutritional deficiencies during the necropsy.
Sex Determination: The gender of a specimen can be determined by examining the animal ventrally. Lactating females have two horizontally spaced, off-centered teats found caudal to the umbilicus. These mammary glands are not always conspicous and may be obscured by pelage. Non-lactating females have even less obvious teats, sometimes only observable as spots of baldness. Females have two openings, the anus and vagina, in the peri-anal region found near the hind flippers; males only have an anal opening. The penile opening can be found on the ventral midline caudul to the umbilicus, as is true for females. Further help in determining sex can be given by palpating the ventral surface in search of the os penis.
Integument Analysis: The final external assessment before necropsy involves a thorough examination of the pelage, skin, orifices (ears, eyes, etc.) and genitals. Discharge, swelling, lesions, parasites, mucus membrane color, missing teeth, etc. should all be noted. Mammary glands should be palpated to express milk, color, consistency and amount (in cc's) also noted. Regions commonly affected by human interaction such as the peduncle, axilla, or snout should be given particular attention. Skin from between the 1st and 2nd digit of the left rear flipper should be removed, 2 inches the standard amount. The entire lower left jaw is also removed for aging. By cutting the mandibular symphysis from the rostrum to the last post-canine teeth (front of snout to throat), the left mandible can then be dislocated from the zygomatic arch through the trimming of connective tissue and muscle.
In the next few days I will be researching internal examination, utilizing Dierauf, L.A. in addition to Pugliares, K.R.
Assessing the condition of a pinniped carcass is a necessary pre-necropsy step, as this can dictate which tests can be done. For example, bacterial tests may only be done on fresh carcasses due to a high probability of contamination in moderately or heavily decomposed specimens. There are five code categories that a stranded seal may fall under:
Code 1: Alive.
Code 2: Fresh carcass
Code 3: Moderate decomposition
Code 4: Advanced decomposition
Code 5: Mummified or skeletal remains
Distinct morphological changes accompany each respective stage, such as bloating evident in moderate decomposing individuals. This can be exhibited by a protruding penis or tongue, and is further differentiated from a fresh carcass by dry mucous membranes, cracked skin and a mild odor. Advancedly decomposed specimens may be found intact, but are severely collapsed, have liquefied internal organs and emit strong odors. Scavenger damage is also often apparent. Mummified or skeletal remains are self-explanatory.
Nutritional Condition: By observing the neck and pelvic regions of a stranded pinniped (deceased or alive), a general assumption about that animal's nutritional condition can be made. This spectrum can range from robust to thin to emaciated. Emaciated individuals exhibit conspicious ribs, protruding pelvic bones and have a visible neck. A healthy, robust individual will appear rounded and have a fusiform body shape. In thin animals, the neck and pelvic bones will show slightly. Blubber thickness measurements will further elucidate any nutritional deficiencies during the necropsy.
Sex Determination: The gender of a specimen can be determined by examining the animal ventrally. Lactating females have two horizontally spaced, off-centered teats found caudal to the umbilicus. These mammary glands are not always conspicous and may be obscured by pelage. Non-lactating females have even less obvious teats, sometimes only observable as spots of baldness. Females have two openings, the anus and vagina, in the peri-anal region found near the hind flippers; males only have an anal opening. The penile opening can be found on the ventral midline caudul to the umbilicus, as is true for females. Further help in determining sex can be given by palpating the ventral surface in search of the os penis.
Integument Analysis: The final external assessment before necropsy involves a thorough examination of the pelage, skin, orifices (ears, eyes, etc.) and genitals. Discharge, swelling, lesions, parasites, mucus membrane color, missing teeth, etc. should all be noted. Mammary glands should be palpated to express milk, color, consistency and amount (in cc's) also noted. Regions commonly affected by human interaction such as the peduncle, axilla, or snout should be given particular attention. Skin from between the 1st and 2nd digit of the left rear flipper should be removed, 2 inches the standard amount. The entire lower left jaw is also removed for aging. By cutting the mandibular symphysis from the rostrum to the last post-canine teeth (front of snout to throat), the left mandible can then be dislocated from the zygomatic arch through the trimming of connective tissue and muscle.
In the next few days I will be researching internal examination, utilizing Dierauf, L.A. in addition to Pugliares, K.R.
Friday, January 8, 2010
Bienvenue a mon blog.
C'est ma première entrée et non, this journal will not be in French (although if I were truly ambitious, this independent study would encompass both marine mammals and the language). Instead, this marks my first entry for my winter of 2010 independent study (my first!) in Applied Marine Mammal Anatomy. The term is rather short for what I plan to study, but essentially I will be distilling anatomical textbooks into a functional approach to necropsies. There will hopefully be a lot of blood in the next coming weeks, as I have signed on to the necropsy team (thank you Rosie), and there are some long-frozen specimens in our on-campus freezer. For now, there are no definite dates, but I should at least start introducing myself to necropsy techniques. My main source these first few weeks will be Marine Mammal Necropsy: An introductory guide for stranding responders and field biologists. (Pugliares, K.R. et al.)
Due to the stochastic nature of strandings, I should be prepared to respond to potential necropsies as soon as possible, and so for this first week I have decided to sidestep an introduction to anatomy and first delve into how to record data for necropsies as well as preliminary sample techniques and data collection. My previous necropsy experiences have introduced me to safety protocols such as utlizing protective gear, sanitizing not only myself but all areas which have come in contact with the specimen during the necropsy, and immediately reporting any cuts that may occur when handling sharp knives/other equipment. These necessary safety measures will be repeated during every necropsy, training and thus proficiency learned through repetition. After all, studying is less likely to cultivate a solid knowledge in safety protocols than practice.
The goal of any necropsy preformed in the United States is to ascertain whether or not human interaction (HI) has affected the specimen. This does not necessarily mean that HI was the direct cause of death, or that because a specimen died of natural causes HI is not present. There are many variables to look at when necropsying, pre- and postmortem injuries just one example, and so it is imperative that when I perform necropsies there is an awareness of these numerous conditions. Objectivity and a conservative eye are indispensible if I want any sort of credibility, and being a liberal college student, this is especially true. With this small but important reminder to myself I begin the more technical route of my studies. Ethics and necropsy logistics merit their own study and attention, but for this independent study I must remember my primary focus.
Morphometrics - To begin to understand how a specimen has come to lie on the necropsy table is to first look at its physical attributes. Details such as age estimations and reproductive status can be determined by examining the weight and length of the specimen and comparing it to known life history stages of each respective species. With time and experience, a clear understanding of what constitutes for example, a young of the year harp seal, emerges and identification can be efficiently correct and swift. For now, this is not something I need to worry about, as more-experienced guides such as Rosemary Seton are around to lend their expertise as I train. Cetaceans are measured from the maxilla to the fluke notch, while pinnipeds are measured from the tip of the muzzle to the end of the tail. Both pinnipeds and cetaceans should face ventral side down while these measurements are done. Pinnipeds require an additional measurement, a curvilinear total length which is measured by laying tape on the top of the dorsal midline, starting at the tip of the nose to the end of the tail while following the body's contour.
Blubber thickness can be an important health status marker for pinnipeds and cetaceans. Unlike length and weight, this measurement is taken in millimeters and is recorded from the muscle-blubber to the skin/fur-blubber interface. Three 2-3 inch long dorsal to mid-ventral cuts are made: the first is made to intersect the dorsal midline, the second to intersect the lateral midline, and the last to interesect the ventral midline which should be made along the axillary plane. Skin and fur thickness should not be included with the measurements.
Well, that marks the end of this first week's introduction to necropsies. Starting next week I will delve into pinniped necropsy techniques, anatomy and tissue sampling. This topic should hold me for about the next 3 weeks and will be accompanied by more traditional studying of anatomy with topics such as the skeletal and muscular system. Until next time, au revoir!
Due to the stochastic nature of strandings, I should be prepared to respond to potential necropsies as soon as possible, and so for this first week I have decided to sidestep an introduction to anatomy and first delve into how to record data for necropsies as well as preliminary sample techniques and data collection. My previous necropsy experiences have introduced me to safety protocols such as utlizing protective gear, sanitizing not only myself but all areas which have come in contact with the specimen during the necropsy, and immediately reporting any cuts that may occur when handling sharp knives/other equipment. These necessary safety measures will be repeated during every necropsy, training and thus proficiency learned through repetition. After all, studying is less likely to cultivate a solid knowledge in safety protocols than practice.
The goal of any necropsy preformed in the United States is to ascertain whether or not human interaction (HI) has affected the specimen. This does not necessarily mean that HI was the direct cause of death, or that because a specimen died of natural causes HI is not present. There are many variables to look at when necropsying, pre- and postmortem injuries just one example, and so it is imperative that when I perform necropsies there is an awareness of these numerous conditions. Objectivity and a conservative eye are indispensible if I want any sort of credibility, and being a liberal college student, this is especially true. With this small but important reminder to myself I begin the more technical route of my studies. Ethics and necropsy logistics merit their own study and attention, but for this independent study I must remember my primary focus.
Morphometrics - To begin to understand how a specimen has come to lie on the necropsy table is to first look at its physical attributes. Details such as age estimations and reproductive status can be determined by examining the weight and length of the specimen and comparing it to known life history stages of each respective species. With time and experience, a clear understanding of what constitutes for example, a young of the year harp seal, emerges and identification can be efficiently correct and swift. For now, this is not something I need to worry about, as more-experienced guides such as Rosemary Seton are around to lend their expertise as I train. Cetaceans are measured from the maxilla to the fluke notch, while pinnipeds are measured from the tip of the muzzle to the end of the tail. Both pinnipeds and cetaceans should face ventral side down while these measurements are done. Pinnipeds require an additional measurement, a curvilinear total length which is measured by laying tape on the top of the dorsal midline, starting at the tip of the nose to the end of the tail while following the body's contour.
Blubber thickness can be an important health status marker for pinnipeds and cetaceans. Unlike length and weight, this measurement is taken in millimeters and is recorded from the muscle-blubber to the skin/fur-blubber interface. Three 2-3 inch long dorsal to mid-ventral cuts are made: the first is made to intersect the dorsal midline, the second to intersect the lateral midline, and the last to interesect the ventral midline which should be made along the axillary plane. Skin and fur thickness should not be included with the measurements.
Well, that marks the end of this first week's introduction to necropsies. Starting next week I will delve into pinniped necropsy techniques, anatomy and tissue sampling. This topic should hold me for about the next 3 weeks and will be accompanied by more traditional studying of anatomy with topics such as the skeletal and muscular system. Until next time, au revoir!
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