ROYAL VETERINARY CADAVERS

Tavishi

Ok so. I was supposed to take a break from posting because, well, moving into college. Hiatus done, I'm back. I've been in college for literally 4 days, but I'm so pumped about the stuff I've been seeing and learning that I need somewhere to dump it all!

This post is just me nerding out about the RVC anatomy museum! My college boasts a huge collection of animal skeletons and plastinated specimens, which is super cool. Everything's organization is kinda scuffed, but ah well. It's very entertaining to just have a table full of various plastinated remains that need to be organized:

Plastination is a really cool specimen fixation process. Plastination allows specimens to be preserved without decay, and while preserving the flesh of the animal. The way this is done is by replacing all the liquid bits with plastic.

First, a specimen is fixed with formaldehyde, which is part of the embalming process. Formaldehyde is generally injected into tissue as formalin, which is formaldehyde gas dissolved into water. Formaldehyde is a cross-linking fixative, which means it uses covalent bonds to link up proteins to give tissues rigidity.

Formaldehyde primarily affects proteins with lysine residues. The way cross-linking works is kinda o-chem-y. Formaldehyde and a protein react, resulting in methylol. Methylol loses water, and forms a Schiff base.

The Schiff base reacts with something else to form a covalent bond. An example of this in the form of fixation would be some sort of water-soluble product joining up with the cytoskeleton, so instead of going to be liquid, it's all sequestered into its own area. In the diagram below, A is what's described, and B is the part where the Schiff base goes off and does its thing.

After fixation comes the process of dehydration. All the yucky bits of dead things are in the liquid. At the RVC, we do this via freeze substitution, which is dunking the cadaver into -25 degree C acetone.

The acetone slowly switches out with the water until finally, we have achieved more than 99% acetone content. The acetone bath is slowly replaced over and over with water, and so it's also repeatedly switched out. In all, this process can take several weeks.

horrible. horrible pun

After the dehydration process, we put the cadaver in a vacuum.

oops

Jokes, that's the wrong vacuum. We have a vacuum chamber. In the long term, we don't want any liquid, but instead, something solid and fixed taking the place of the water. So, we draw out the acetone by boiling it in a vacuum, while submerging the cadaver in a silicone polymer solution. This process takes even longer than the freeze substitution, lasting several months. In the long term, we don't want any acetone left. All the leftover acetone is directed instead to a solvent separator.

Finally, we have to cure the silicone by putting it in a chamber full of Biodur S6 gas. It takes 48 hours to fully harden the tissue. In the end, we want the cadaver to not be wet to the touch anymore.

Below is an exhaustive list of all the pinniped specimens in the museum:

1. Walrus skull: No tusks, but very cool. Judging by the mandible, I'm taking a guess that it's a female (see the mandibular process and condyles.) Walruses have a great degree of sexual dimoprhism.

2. Crabeater seal skull: the teeth are so cool omg. I never thought I'd be able to see this ever?

3. Gray seal skull: male specimen, labeled by museum. These are native to the UK, and I've seen some in Cape Cod!

4. Leopard seal skull: freaking huge. I know how big these pinnipeds are but the scale is so fascinating to see in person. The teeth are so cool. I'm assuming this is a female, with much less confidence than the walrus.

5. Harbor seal skull: I've seen one of these before! As tiny as expected.

6. South American sea lion skull: Totally unexpected considering the other pinniped specimens. Tropical skull??? Anyways, very cool. Almost certainly a female, judging by the size (males are generally much larger with a much more pronounced sagittal crest).

7. Grey seal pelvis, hind limb, and forelimb: I've been studying these bones so much, especially in the context of locomotion, so it's really cool to be able to identify all the nooks and crannies of the bones (me when I can see the subscapular fossa and I know what it is!?!?!??!).

8. Harbor seal thoracic vertebrae, ribs, sternum, and xiphoid process: askldjflkasdjfalskdjfa I'm imagining all the ligaments. You can see the remnants of the nucleus pulposus too!!!!

9. Seal bronchial tree cast and heart: no words. It's so magical seeing these things and understanding them.

Ok, stay tuned for more college updates, because I'm having such a wonderful time so far. For legal reasons, I'm not sure what photos I can and cannot add but, if I'm able to get permission, I'll make a post mostly of just photos!