A cadaver is a human body voluntarily donated for medical education and scientific research, serving as an invaluable resource for training future healthcare professionals. Preservation is necessary because it halts the natural process of decomposition, which begins shortly after death. Preservation methods maintain the body’s structural integrity, allowing students and surgeons to study anatomy and practice complex procedures over an extended period, sometimes lasting for months or even years.
The Standard Preservation Method: Chemical Embalming
The most common technique used to prepare cadavers for anatomical dissection is chemical embalming, often referred to as “wet” preservation. This process typically begins with arterial injection, where a preservative solution is pumped into the vascular system to distribute the chemicals throughout the body. Simultaneously, blood is drained from a vein, ensuring the fluid reaches the smallest capillaries and fixates the tissues from within.
The composition of the embalming fluid is specifically designed for long-term preservation, differing significantly from that used in funeral preparation. Anatomical solutions contain a high concentration of fixatives, such as formaldehyde (formalin) or glutaraldehyde, which chemically cross-link proteins to stop cellular breakdown and microbial growth. These agents solidify the tissue structure, preventing decay that would otherwise render the specimen unusable.
A complete embalming solution also contains humectants, most commonly glycerol or ethylene glycol, which draw moisture into the tissues to counteract the drying effects of the fixatives. This maintains the pliability and flexibility of muscles and joints for dissection and surgical training. Additionally, disinfectants like phenol are often included to sterilize the body and prevent mold or fungal growth during storage.
The primary goal of preservation embalming is functional longevity, not cosmetic appearance, which contrasts with funeral embalming that uses lower fixative concentrations. The higher concentration of chemicals in academic preservation ensures the cadaver can be used intermittently for a full academic year or more. A soft-fix technique, such as the Thiel method, uses lower concentrations of formaldehyde and often includes salts or alternative chemicals to produce a specimen that is more flexible and realistic for surgical simulation.
Plastination: An Alternative for Permanent Display
Plastination represents a different preservation method, resulting in specimens that are dry, durable, and suitable for permanent display. This technique begins with chemical fixation, often utilizing the same formalin-based solutions as traditional embalming to halt decay. Following fixation, the specimen is dissected and prepared to highlight specific anatomical structures before the multi-step process begins.
The first step is dehydration, where the water and lipid content of the tissue are systematically replaced by an organic solvent, such as acetone. The specimen is immersed in a cold acetone bath for several weeks until the body is completely saturated with the solvent. This prepares the tissue for the next phase of infiltration.
The step of forced impregnation occurs when the solvent-saturated specimen is placed into a bath of liquid polymer, such as silicone rubber, epoxy, or polyester resin. The bath is then subjected to a vacuum, causing the acetone to vaporize at a low temperature. As the solvent leaves the tissue, the vacuum pressure forces the liquid polymer deep into the cells, replacing the acetone entirely.
Finally, the polymer-infused specimen is cured using heat, gas, or ultraviolet light, depending on the resin used. The resulting plastinate is a solid, non-toxic, and odorless specimen that retains the original anatomical detail. Because the polymer is inert and stable, these specimens can be handled directly and do not require specialized storage, making them ideal for permanent teaching models or museum exhibits.
Long-Term Storage and Maintenance
Once a cadaver has undergone chemical embalming, specific protocols are required to ensure its long-term viability for study. Preservation requires continuous maintenance to prevent desiccation and microbial contamination. Cadavers are typically stored in specialized facilities, such as cooled rooms or mortuary refrigerators, to maintain a consistent, controlled environment.
Temperature and humidity controls are important, as excessive heat accelerates chemical breakdown, and dryness leads to tissue shrinkage and hardening. When not actively being dissected, the cadaver is usually covered with a heavy, preservative-soaked cloth, which is then wrapped in a plastic sheet or bag. This barrier prevents the embalming fluid from evaporating and keeps the external tissues moist and pliable.
During extended use, exposed surfaces risk drying out and becoming stiff, so supplemental chemical application is necessary. Technicians routinely spray the cadaver with a wetting solution, often a diluted version of the original fluid or a solution containing humectants and a fungicide. For very long-term storage, some institutions utilize large immersion tanks filled with a low-concentration preservative fluid, where the entire cadaver can be submerged when not in use.