Macroscopic Anatomy of the Ringed Seal [Pusa (Phoca) hispida] Lower Respiratory System

Abstract

This investigation serves to document the normal anatomical features of the lower respiratory tract of the ringed seal [Pusa (phoca) hispida]. Evaluation of embalmed specimens and tracheobronchial casts showed that the right lung of this seal consists of four lobes while the left has only three lobes. The ventral margins of the lungs do not reach the sternum causing them to form the boundary of the broad recessus costomediastinalis. Lung lobation corresponds with bronchial tree division. Pulmonary venous drainage includes right and left common veins draining ipsilateral cranial and middle lung lobes, and one common caudal vein draining both caudal lobes and the accessory lobe. The right and left pulmonary arteries divide into cranial and caudal branches at the level of the principal bronchus. The ringed seal has three tracheobronchial lymph nodes. The trachea has an average of 87 cartilages that exhibit a pattern of random anastomoses between adjacent rings. The trachea exhibits to a small degree the dorsoventrally flattened pattern that is described in other pinnipeds. The tracheal diameter is smaller than that of the canine.

Macroscopic Anatomy of the Saimaa Ringed Seal (Phoca hispida saimensis) Lower Respiratory Tract

“…The number of tracheal rings (85 and 86) in our Saimaa ringed seal specimen corresponded with those (an average of 87) of previous seal studies (Sokolov et al, ; cited in Smodlaka et al, ). Compared to some other phocid species, however (Boyd, ; Frost and Lowry, ; Smodlaka et al, ; Moore et al, ), the Saimaa ringed seal had no gaps or slips in any of their tracheal cartilage rings. However, the dorsal part of most of the rings was thin as it dissolved quickly, especially in the caudal part, after the trachea was placed in the hypochlorite treatment.…”

“…Similarly to that of ringed seal (Smodlaka et al, ), the tracheal diameter (11 mm–12 mm) of Saimaa ringed seal is small compared to its body size. Also, similarly to other pinnipeds (Boyd, ; Smodlaka et al, ), the trachea of the Saimaa ringed seals was partly flattened. Moore et al () recently summarized the discussion on the role of tracheal morphology on the diving ability of mammals.…”

“…The Saimaa ringed seal catches fish by rapid forward movements of the head and neck (M. Kunnasranta, personal communication). The dorsoventrally compressed, flexible caudal trachea may ensure that the neck of the Saimaa ringed seal can efficiently bend during the retraction phase despite the lack of incomplete caudal tracheal rings which add compliance to an overall rigid trachea in some other phocids (Smodlaka et al, ; Moore et al, ). Histological studies are needed to determine the type and amount of tissue present between rings lengthwise which may potentially indicate differences in flexibility between the bronchial regions.…”

“…Interestingly, varied degrees of lobation in lungs of northern pinnipeds has been reported including the ringed seals (Sokolov et al, ; Frost and Lowry, ; Koster et al, ; Smodlaka et al, ). In this study, the lobation became more readily visible during the natriumhypoclorite bath (Fig.…”

Posterior Respiratory Apparatus of Inia geoffrensis and Sotalia fluviatilis: Structure and Ultrastructure

“…These results are similar to those found in the study by Henry et al (1983), which shows that tracheal rings of many cetaceans vary in their cartilages in different regions of the organ, these being generally dorsally open (Smodlaka et al, 2009). In our findings, both in the cranial, middle and caudal regions, the cartilages were dorsally open.…”