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.