The UOEHAssociationUOEH Association ofofHealth Health Sciences J. UOEH, 2(4): 463-468 (1980) 463 (Original) Corrosion Anatomy of the Eparterial Bronchi in the Rough Toothed Porpoise, Steno bredanensis Teruyuki HoJo DePartment of Anatomy and Anthropology, Schooi of Medicine, Uhaiversit), of OccuPational and Environmental Heaith, JaPan, Kitakyushu 807, faPan Abstract: The lungs of a rough toothed porpoise, Steno bredanensis, were $tudied from the corrosion anatomical viewpoint by preparing the corrosion cast ift sit". It is the most suitable meLhod of studying the three-climensional relationship of the tracheobronehial tree and the pulmonary vascular tree within the lungs, There is one lobe on each side, but feur secondary bronchi on the right, and three secondary ones and a cardiac impression on the left. There are three eparterial bronchi: the tracheal bronchus and the second closest bronchus to the cranium on the right side; the closest bronchus ,to the cranium en the left, While the pulmonary arteries ge along almost the samel course of the tracheobronchial tree, the pulmonary veins come intersegmentally from the peripheral parts making a four-forked convergence ventrally. One dorsal vein adds to this conver- gence, resulting in a five-forked form. Key tvords: corrosion anatemy, eparterial bronchus, rough toothed porpoise, (Received 16 August 1980) Introductien Various patterns of the regional relationship between the tracheobronchia] tree and the pulmenary vascular one in the lungs of sea mammals have been attracting the at- tention of not a few investigators (Aeby, 1880; Boeckh, 1914; Huntington, 1920; Ping, 1926; Marcus, 1937; Arai, 1958; Brown, 1958; Sakai & Tsuneishi, 1962; Hojo, l975, 1979; Yamasaki', et al., 1977). Among their various patterns, the eparterial bronchus, which was first described by Aeby, has been one of the rnain objects from the comparative point of view, including human subjects, There are many textbooks on .human anatomy in which the eparterial bronchus in humans is described, one being Grant:s Method of Anatomy (Basmajian, 1975). But, until now, there has been none on the eparterial bronchus in the lungs of the porpoise, Steno bredanensis, family DetPhinidae, class Mammalia. That is to say, regarding the lung$ of Steno bredanensis, the problem of the regional relationship between the tracheobronchial tree and the pulmonary vascular one remains unsolved. Further, the comparative anatomical study of the lungs of Franciscana (PontoPoria blainvillei), compared with those other cetaceans, was recently made by Yamasaki et al. (1977). But witheut regarding the corrosion cast they obtained conclusions only on the NII-Electronic Library Service The UOEHAssociationUOEH Association ofofHealth Health Sciences 464 T. HoJo ramifications and a few descriptiens on the regional relationship between them in their study. In order te make clear and describe accurately the three-dimensional relationship between them, the author thinks the most suitable method is to prepare the corrosien cast of the lungs in situ. In this paper the author describes some conclusions obtained by preparing the corrosion cast of the lungs of the rough toothed porpoise and by referring to Tucker & Krementz (1957), Arai (1958), Hejo (1975, 1979), and Yamasaki et al. (1977). Materials and Methods In order to make clear the three-dimensional relationship of the pulmonary vascular tree to the tracheobronchial one, the author prepared the corrosion cast of the lungs of the porpoise in situ, injecting yellow resin into the most cranial part of the trachea, red resin into the pulmonary arteries, and blue resin into the pulmonary veins. The injection technique was slightly changed from that of Hojo (1974, J.975). The inhaled lungs in situ were iinjected to prevent, as little as possible, the collapse of the shape. When the injection materials hardened, the lungs were removed from the thorax and placed in a strong solution of hydrochloric acid, until the lung tissue had been corroded. After corrosion, they were washed by running water to make the cast of the tracheobrenchial tree and the pulmonary vascular tree. The subject used in this study was the rough toothed porpoise, Steno bredanensis which was also used in the anatomical study of the liver by Hojo & Mitsuhashi (1975). It was an adult male, 241 cm in body length, caught in the North Pacific Ocean neighbor- ing Japan. Results and Discussion It is generally known that the lungs of the porpoise and the dolphin have no iobulation on either side. In the author's observations the lungs of the rough toothed porpoise which are bell-shaped, have no fissure on each side and the right lung is considerably larger than the left. As shown in Figs, 1 and 2, the tracheobronchial tree and the pulmonary vascular tree show an asymmetrical pattern. From the right lateral wall the tracheal bronchus leaves the trachea at an angle of about 200, at the point about 70 mm craniad from the bifur- cation of the trachea. The tracheal bronchus, 15 mm in diameter and 77 mm long, gives off the tertiary bronchi which supplies the cranial part of the lung. Because the rough toothed porpoise has one lobe on each side and the tracheal bronchus supplies the cranial part of the right lung, the tracheal bronchus is theught to be the secondary bronchus. The position of the Lracheal bronchus is more craniad than those of the lungs of the PontoPoria, the inia and the Platanista which were reported by Yamasaki et al. (1977). NII-Electronic Library Service TheTheUOEHAssociation UOEH Association ofofHealthSciences Health Sciences EparterialBronchus in theRoughToothedPorpeise 461) Fig,L Fig, 2. Figs, 1 and 2. Ventral view of the porpoise lungs. Fig. 3, Dorsal view of the porpoise lungs, T: Trachea ETB: Tracheal bronchus (Epartetial bronchus) PB: Principal bronchus A: Pulmonary artery V; PuEmonary vein ESBR: The right second closest bron- chus to the cranium(Eparterial bronchus) ESBI): The left closest bronchus to the cranium (Eparterial bronchus). Fig. 3, AR and AL: Right and left pttlmonary artery NII-Electronic Library Service The UOEHAssociationUOEH Association of Health Sciences 466 T. HoJo The trachea biiurcates two bronchi; the right and the left, principal and they make an angle of 250. In the right lung, the second closest secondary bronchus to the cranium branches ofii dorsolaterally about 10 mm long and 12 mrn in diameter. About 30 mm distant caudad from the branching site of the second closest secondary bronchus to the cranium, the principal bronchus gives off two seconclary bronchus, the ventral and the dorsal, which become the third closest secondary brQnchus to the cranium. The ventral one is 10 mm in diameter and 10 mm long. The dorsal one, almost the same size as the ventral one, branches off slightly caudad. Regarding the bronchial tree, Brown (1958) pointed out in his explanation of the preparation ef the resin cast in Proceedings of the Anatomical Society that t.he porpoise Iungs show a distinctly unequal bronchial pattern, including the tracheal bronchus on the right side. These results are almost the same as the present author's. But the kinds of porpoises used jn Brown's study are unknown and the relationship between the bronchial tree and the pulmenary vascular tree was also not shown. The pulmonary artery biturcate at the position of about 26 mm distant caudad from the bifurcatien of the trachea, is situated ventra]ly to the leit prlncipal bronchus. As shown in Fig. 1, the pulmonary artery in the right Lung gives off its first branch into the cranial part of the right lung goin.cr across the right principal bronchus and the tracheal bronchus, situated ventrally to the bronchial tree. After the pulmonary artery gives off the closest braneh to t'he cranium ancl goes across the right principal bronchus, it passes between the second clesest secondary bronchus to the cranium and the third closest secondary bronc.hus to the cranium, and goes caudad Iying dorsally to the third closest secondary bronchus to the cranium in the dorsolatera] course along that oi the right principal bronchus (Fig. 3). On the other hand, the left lung has no tracheal bronchus. The closest secondary bronchus to the cranium, 15 inm in diameter and 20 mm long, supplying the cranial part of the leit lung, brancbes off dorsolat.erally at the almost same positio]i of the branching of the second c]osest secondary bronchus to the cranium in the right lung. But this closest secondary bronchtis of the left lung is considerably thicker, larger, and longer than the second closest secondary bronchus to the cranium in the right lung. Further, the iormer exLends more craniad than the latter. Ill each side of the lungs the number and shapes of other secondary bronchi are observr- ed, but the interrnediate bronchi in the medial side start from the lefL principal bronchus. These intermediate secondary bronchi are thicker and longer in the lelt lung than those in the right lung. There are more than three in the left. The feature of the rough toethed porpoise is that ]'t has more-than-three medial intermediate secondary bronchi in the left lung. This characteristic feat/ure is not observed in other sea mammals such as the seal (Arai, 1958; Sakai & Tsuneishi, 1962), the harbor seal (Hojo, l975), and the otary (Hojo, 1979). In addition to this, the left principal brencus shows censiderable concavity in the medial side. This concavit}i is the cardiac impression. NII-Electronic Library Service The UOEHAssociationUOEH Association ofofHealth Health Sciences Eparterial Bronchus in the Rough Toothed Porpoise 467 The pulmonary artery in the left lung branches off from the bifurcation of the pulmonary artery and goes ventrally to the closest secondary bronchus, giving off the colsest branch to the cranium. After that, the pulmonary artery passes between the closest secondary bronchus and the second closest secondary one, and goes caudad Iying dorsally to the latter, in a course aiong that of the left principal bronchus.