To expose body cavities, there are two ways of proceeding.
- Once the initial incision is given from base of chin to symphysis pubis, the skin and fat layers can be strapped off exposing the underlying muscles. The origin of each muscle is then given a cut on its lateral end and reflected medially.
- Another way is to reflect skin, adipose and muscle all together, laterally exposing the underlying rib cage and abdominal cavity.
Removing the neck structures
To remove the neck structures, a 10-12 cm high wooden/metallic block is placed under shoulders of cadaver, which allows head to fall back, extending the neck. A stout knife is passed under skin of upper neck until floor of mouth is reached. This knife is then run around inside of mandible and tongue is freed. Tissue at back and sides of pharynx are then divided and a cut is given through tonsillar area. Tongue is grasped by fingers passed behind mental symphysis and drawn down. Remaining laryngeal tissues are divided laterally, freeing the neck structures and carotids.
In case of any suspicious injuries to the neck structures, it should be removed in the end following removal of organs from all three body cavities, viz. abdominal, thoracic and cranial cavities.
Articulating surfaces of sternoclavicular joints can be located by moving shoulder tip on either side. Once they are located, a cartilage knife is introduced vertically and laterally to disarticulate the joints. In elderly, the joint might be ankylosed where handsaw and shears might be needed. Once the joints are separated, a stout knife is penetrated through second intercostal space and dragged downwards along para sternal line, medial to costo-chondral junction till diaphragm is reached. The sternum and medial rib segments are free now. This section is lifted and dissected away from the mediastinum, keeping the knife close to the sternum, to avoid puncturing the pericardium. The degree of inflation of the lungs should is assessed at this point to note for any asymmetry, complete or partial collapse, emphysema or over distension.
In case pneumothorax is suspected, the chest wall can be punctured following collection of water between fold of reflected tissues and chest wall along mid axillary line to note for presence of bubbles. Marked tension pneumothorax would release a hiss of escaping air when tip of knife penetrates parietal pleura. Both these findings would be negative in case there is a patent communication between parietal pleura and bronchioles.
If pleural adhesion is present, careful removal with help of curved scissors can be helpful. Any effusions or collection of blood should be noted mentioning their color, amount and smell. This can be done by inserting a sponge, soaking it and removal squeezing it in a measurable vessel. Care must be applied as the fractured piece of rib may act as a sharp pointed object, causing injury to the examiner.
Abdominal cavity, pelvic cavity and their removal en-masse
Now that the chest organs are free, diaphragm is incised. Non-operating hand should pull liver and spleen medially, stretching the left leaf of the diaphragm, while curved scissors are used to cut towards the costal margins, posteriorly under the organ then through cruciate ligaments and caudally behind the kidney. The cut then curves up over the psoas muscles, ending at pelvic brim. Same procedure is done on the opposite side by shifting the position of dissector to opposite side of the table.
The chest organs along with neck structures are then lifted and gently pulled forward towards the feet of the deceased. If any resistance is offered by the block being removed, careful cutting of cruciate ligaments must be re-done. Iliac vessels and ureters are last to cut through and the whole mass of viscera is then taken away to dissection bench where running water is available for cleaning.
Abdominal cavity should be inspected for ascites, fecal fluid, pus or blood. Loops of bowel are inspected for anomalies like infarction, perforation and distension. Infarction must be distinguished from hypostasis. Posterior part of bowel is examined for retroperitoneal hemorrhage due to ruptured aorta or aneurysms.
The testes are pushed upward through inguinal canal widened by blunt dissection. Ovaries in females are incised and tubes are examined. Uterus is sliced along midline from fundus to cervix and any mass or product of conception, if present, must be subjected to histopathological analysis.
In women, the ovaries and tubes are mobilized forwards and the knife passed around the wall of the pelvic bowl, then in front of and below the bladder. In cases where sexual assault or abortion is suspected, a special technique is required, involving pelvic block dissection.