Dissection

Dissection (from Latin dissecare "to cut to pieces"; also called anatomization) is the dismembering of the body of a deceased animal or plant to study its anatomical structure. Autopsy is used in pathology and forensic medicine to determine the cause of death in humans. Less extensive dissection of plants and smaller animals preserved in a formaldehyde solution is typically carried out or demonstrated in biology and natural science classes in middle school and high school, while extensive dissections of cadavers of adults and children, both fresh and preserved are carried out by medical students in medical schools as a part of the teaching in subjects such as anatomy, pathology and forensic medicine. Consequently, dissection is typically conducted in a morgue or in an anatomy lab.

Dissection has been used for centuries to explore anatomy. Objections to the use of cadavers have led to the use of alternatives including virtual dissection of computer models.

In the field of surgery, the term "dissection" or "dissecting" means more specifically the practice of separating an anatomical structure (an organ, nerve or blood vessel) from its surrounding connective tissue in order to minimize unwanted damage during a surgical procedure.

Plant and animal bodies are dissected to analyze the structure and function of its components. Dissection is practised by students in courses of biology, botany, zoology, and veterinary science, and sometimes in arts studies. In medical schools, students dissect human cadavers to learn anatomy. Zoötomy is sometimes used to describe "dissection of an animal".

A key principle in the dissection of human cadavers (sometimes called androtomy) is the prevention of human disease to the dissector. Prevention of transmission includes the wearing of protective gear, ensuring the environment is clean, dissection technique and pre-dissection tests to specimens for the presence of HIV and hepatitis viruses. Specimens are dissected in morgues or anatomy labs. When provided, they are evaluated for use as a "fresh" or "prepared" specimen. A "fresh" specimen may be dissected within some days, retaining the characteristics of a living specimen, for the purposes of training. A "prepared" specimen may be preserved in solutions such as formalin and pre-dissected by an experienced anatomist, sometimes with the help of a diener. This preparation is sometimes called prosection.

Most dissection involves the careful isolation and removal of individual organs, called the Virchow technique. An alternative more cumbersome technique involves the removal of the entire organ body, called the Letulle technique. This technique allows a body to be sent to a funeral director without waiting for the sometimes time-consuming dissection of individual organs. The Rokitansky method involves an in situ dissection of the organ block, and the technique of Ghon involves dissection of three separate blocks of organs - the thorax and cervical areas, gastrointestinal and abdominal organs, and urogenital organs. Dissection of individual organs involves accessing the area in which the organ is situated, and systematically removing the anatomical connections of that organ to its surroundings. For example, when removing the heart, connects such as the superior vena cava and inferior vena cava are separated. If pathological connections exist, such as a fibrous pericardium, then this may be deliberately dissected along with the organ.

Dissection is used to help to determine the cause of death in autopsy (called necropsy in other animals) and is an intrinsic part of forensic medicine.

Human dissections were carried out by the Greek physicians Herophilus of Chalcedon and Erasistratus of Chios in the early part of the third century BC. Before then, animal dissection had been carried out systematically starting from the fifth century BC. During this period, the first exploration into full human anatomy was performed rather than a base knowledge gained from 'problem-solution' delving. While there was a deep taboo in Greek culture concerning human dissection, there was at the time a strong push by the Ptolemaic government to build Alexandria into a hub of scientific study. For a time, Roman law forbade dissection and autopsy of the human body, so anatomists relied on the cadavers of animals or made observations of human anatomy from injuries of the living. Galen, for example, dissected the Barbary macaque and other primates, assuming their anatomy was basically the same as that of humans, and supplemented these observations with knowledge of human anatomy which he acquired while tending to wounded gladiators.