The pleural cavity of the Nile crocodile is divided into two separate cavities by means of a complete
 mediastinum. The pleural cavity contains the lungs, while the heart is situated in its own cavity, the
 pericardial cavity. The pleural cavity is separated from the hepatic coelom, which contains the liver, by
 the post-pulmonary membrane. The hepatic coelom is separated from the peritoneal cavity by the post-hepatic
 membrane. The peritoneal cavity contains the abdominal organs.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. 
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Kotze, Sanet H.

Van der Merwe, N.J.

The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. 
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.The pleural cavity of the Nile crocodile is divided into two separate cavities by means of a complete
 mediastinum. The pleural cavity contains the lungs, while the heart is situated in its own cavity, the
 pericardial cavity. The pleural cavity is separated from the hepatic coelom, which contains the liver, by
 the post-pulmonary membrane. The hepatic coelom is separated from the peritoneal cavity by the post-hepatic
 membrane. The peritoneal cavity contains the abdominal organs.mn201

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Onderstepoort Journal of Veterinary Research, 60:219- 222 (1993) The topography of the thoracic and abdominal organs of the Nile crocodile (Crocodylus niloticus) N.J. VANDER MERWE1 and S.H. KOTZE2' ABSTRACT VAN DER MERWE, N.J. and KOTZE, S.H. 1993. The topography of the thoracic and abdominal organs of the Nile crocodile (Crocodylus niloticus) . Onderstepoort Journal of Veterinary Research, 60:219- 222 The pleural cavity of the Nile crocodile is divided into two separate cavities by means of a complete mediastinum. The pleural cavity contains the lungs, while the heart is situated in its own cavity, the pericardia! cavity. The pleural cavity is separated from the hepatic coelom, which contains the liver, by the post-pulmonary membrane. The hepatic coelom is separated from the peritoneal cavity by the post-hepatic membrane. The peritoneal cavity contains the abdominal organs. INTRODUCTION Brief studies of the macroscopic anatomy of the gastro-intestinal tract of Alligator mississippiensis (Guibe 1970; Reese 191 0; Evans 1986) and Alligator sclerops (Guibe 1970; Grunwald 1931) are available, but similar studies of the Nile crocodile, Crocodylus niloticus, have been neglected in the literature. Dunc-ker (1979) , however, did report on the coelomic cavi-ties of crocodilians. The present study was carried out to describe and document the topography of the thoracic and abdominal organs in the Nile croco-dile. MATERIALS AND METHODS Eight two-year-old female Nile crocodiles, with nose to tail lengths varying between 1,1 and 1 ,4 m, were 1 Department of Anatomy, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 011 0 South Africa 2 Department of Anatomy, Faculty of Medicine, University of Pretoria, P.O. Box 2034, Pretoria, 0002 South Africa Received 22 June 1993-Editor obtained from a breeding farm. These animals were shot, exsanguinated and routinely skinned. The tho-racic and abdominal ribs were exposed and counted. The thoracic and abdominal cavities were opened by removing the dorsal thoracic and abdominal body walls in three specimens and, similarly, the ventral body wall in five specimens. At this stage the speci-mens were photographed and the topography of the thoracic and abdominal organs was illustrated. Four specimens were eviscerated and the gastro-in-testinal tracts were dissected to reveal the different parts. These specimens was then illustrated or pho-tographed. RESULTS The Nile crocodile has 11 to 13 thoracic ribs and six to seven abdominal ribs. At the thoracic inlet the tra-chea is situated to the left of the oesophagus which lies in the midline within the dorsal mesentery. The trachea then turns abruptly to the right before di-viding into a left and right primary bronchus (Fig. 1). The pleural cavity is divided into separate left and right cavities by means of a complete mediastinum. The cavities are roughly triangular in shape, with the 219 Topography of the Nile crocodile (Crocodylus niloticus) FIG. 1 A semi-schematic drawing of a ventral view of the open-ed plural and peritoneal cavities a - Post pulmonary membrane b - Luhgs c - Heart with its attachment to the post-pulmonary membrane c' d - Liver d - Gall bladder (within hepatic coelom) e - Post hepatic membrane (partially removed) f - Stomach g - Fat body h - Loops of jejunum and ileum i - Pancreas j - Duodenum (showing double loop) k - Rectum I - Kidneys base situated caudally and the apex terminating in cupulae, both extending a short distance (± 15 mm) beyond the first thoracic rib. Caudally, the pleural cavity is bound by a post-pulmonary membrane (Fig. 1) and divided into left and right cavities by means of a complete mediastinum. The diaphragmatic sur-faces of the two lungs are attached to the post-pul-monary membranes, while the caudal third of the medial borders are attached to the mediastinum. The four-chambered heart, with a cranio-caudal orien-220 FIG. 2 A semi-schematic drawing of a dorsal view of the pleural and peritoneal cavities with post-pulmonary and post-hepatic membranes removed a - Lungs b - Right lobe of liver c - Stomach d - Fat body e - Jejunum and ileum f - Rectum g - Kidneys h - Spleen i - Gonads tation , is situated between the fourth and eighth tho-racic ribs. The apex of the heart is attached to the pericardia! sac by means of a ligament. A ligamen-tous attachment in the midline exists between the pericardia! sac and the post-pulmonary membrane. (Fig. 1). The post-pulmonary membrane extends to between the ninth thoracic and first abdominal ribs. The dorsal part of the post-pulmonary membrane is completely membranous, while the ventral third is muscular. The liver, which consists of right and left lobes, is situated in its own coelomic cavity, the hepatic coe-lom, which is bound cranially by the post-pulmonary membrane and caudally by the post-hepatic mem-brane (Fig. 1 ). These two membranes are intimately associated with the cranial and caudal surfaces of the liver, respectively. The right and left pleural cavi-ties communicate with the hepatic coelom by means of two openings situated left and right dorsally in the membranous part of the post-pulmonary membrane. A sheet of striated muscle extends from the pubis and is inserted on the ventral and lateral attachment line of the post-hepatic membrane. The gall bladder is situated to the right of the midline within the hepa-tic coelom (Fig . 1) . The bile duct opens in the proxi-mal part of the duodenum. The stomach is situated to the left of the abdominal cavity, between the tenth thoracic and the sixth ab-dominal ribs, with the greater curvature facing to the left (Fig . 1 and 2). A very acute angle is present be-tween the cardia and pylorus (Fig . 2) . An oval to round, dorso-ventrally flattened , encapsulated portion of adipose tissue, the so-called "fat body" , occupies the right cranial part of the abdominal cavity (Fig . 1) . The duodenum is arranged in the form of a double loop on the right, with the pancreas situated between the arms of the outer loop. (Fig . 1). The pancreas also extends to the cranial broad part of the spleen and along the proximal part of the jejunum. The lat-ter part is attatched to the dorsal body wall. The ileum and jejunum, which are of equal length, fill the right and left side of the peritoneal cavity. The prox-imal part of the jejunum is firmly attached to the dor-sal body wall. The mesentery then lengthens to allow free coiling of the remaining portions of the jejunum and ileum. The rectum (in the midline) extends into the cloaca (Fig . 1). The kidneys are situated cauda-dorsally, partly with in the pelvic cavity (Fig . 2) . The gonads lie crania-medially to the kidneys (Fig. 2). The spleen is pear-shaped with the broad end point-ing cranially and it is attached to the dorsal body wall between the second and third abdominal ribs (Fig . 2). The dissection of the gastro-intestinal tract revealed the stomach of which the minor curvature displayed a very acute angle, resulting in the cardia and py-lorus lying adjacent to each other. A pyloric antrum or dilatation is separated from the main part of the stomach by a distinct sphincter. (Fig. 3). The duode-num is arranged in a double U-shaped loop (Fig . 1 and 3), with the proximal part of the duodenum form-ing the inner loop and the distal part the outer loop. The jejunum is situated between the duodenum and ileum. The beginning of the latter is demarcated by the presence of theA. mesenterica crania/is. An ilea-rectal junction is present where the narrow ileum abruptly changes into the wide rectum . The rectum continues into the cloaca (Fig . 3). N.J. VAN DER MERWE & S.H . KOTZE DISCUSSION The findings of the present study confirm Duncker's (1979) statement that the crocodilians possess a pleural cavity, hepatic coelom and peritoneal cavity . This is in contrast with the Chamaeleonidae, where only the ventral part of the post-pulmonary septum is present; and dorsally, the pleural and peritoneal cavities are continuous, forming a pleura-peritoneal cavity (Duncker 1979) . In the vertebrate embryo, the diverticulum hepaticum grows into the septum transversum as the anlage of the liver (Starck 1955) . The septum transversum forms the connective tissue component of the liver and , in higher vertebrates, the major part of the diaphragm. In the crocodile the septum transversum presumably not only forms the connective tissue of the liver, but also the post-pulmonary and post-hepa-tic membranes. In the Chamaeleonidae the dorsal part of the septum transversum either does not de-velop, or it regresses at a later stage of develop-ment. The sheet of striated muscle extending from the pubis to the post-hepatic membrane seen in the present study, corresponds to the Musculus dia-phragmaticus described by Duncker (1979) . The appearance of the stomach in Crocodylus niloti-cus conforms to that in Alligator mississippiensis in that there is an acute angle between the cardia and the pylorus, and a pyloric antrum is present (Chias-son 1962; Guibe 1970; Evans 1986). In Alligator sclerops (Grunwald 1931) the stomach is rather elon-gated without a pyloric dilatation as is the case in snakes and lizards (Goin & Gain 1971) . The double loop of the duodenum in the Nile croco-dile is in contrast with A. mississippiensis (Chiasson 1962; Guibe 1970; Evans 1986) and A. sclerops which exhibit only a single loop (Grunwald 1931 ). The small i'ntestine forms coils in all crocodilians (Chiasson 1962; Guibe 1970; Evans 1986) , as is the case in snakes and lizards (Gain & Goin 1971; Stid-worthy 1971 ). However, snakes and lizards have a colic caecum, which is absent in crocodiles (Gain & Go in 1971) and this is confirmed in the present study. In all reptiles an abrupt transition from small to large intestine is a prominent feature (Goin & Goin 1971 ; Hyman 1942), which is also the case in the Nile crocodile. The "fat body" was described by Rathke in 1862 (Vorstman 1939). However, little reference has been made to this structure in the literature, presumably due to the fact that most autopsies were done on old emaciated zoo specimens in which it had disap-peared (Vorstman 1939). In crocodiles the fat body is associated with the dorsal mesenterium, whereas in snakes the paired fat bodies are associated with the gonads (Vorstman 1939). 221 Topography of the Nile crocodile (Crocodylus niloticus) FIG. 3 A photograph of the stomach and intestines removed a - Stomach b - Cardia c - Piloric dilatation d - Duodenum (showing double loop) e - Jejunum and ileum f - lleo-rectal junction (note the abrupt transition from ileum to rectum) g - Rectum As the specimens examined were immature females, no definite conclusion in respect of the topography of active gonads could be made. CONCLUSIONS This study provides information hitherto unknown as to the topography and organs of the Nile crocodile. Some similarities to other crocodilians are present, but some unique features also occur. ACKNOWLEDGEMENTS We would like to thank Mr & Mrs Kuhlmann, lzintaba Croco Farm, De Wildt, South Africa, for specimens supplied; Mrs H. Smit for the photography, Ms C. Seegers for the illustrations, Dr F.W. Huchzermeyer for reading the manuscript, and Prof. G.A. Smith for his help in initiating the study. REFERENCES CHIASSON, R.B. 1962. Laboratory anatomy of the alligator. Dubuque, Iowa: WM. C Brown Co. 222 DUNCKER, H.R. 1979. Coelomic Cavities, in Form and function in Birds. Vol. I, edited by A.S. King & J. MacLelland. London, New York, Toronto, Sydney, San Francisco: Academic Press. EVANS, H.B., 1986. Reptiles, introduction and anatomy, in Zoo and Wildlife Medicine, 2nd edition, edited by M.E. Fowler. Philadelphia: W.B. Saunders Co. GOIN, C.J. & GOIN O.B. 1971. Introduction to herpetology. San Francisco: W.H. Freeman & Co. GRUNWALD, E. 1931. La Torsion intestinale chez les reptiles. Archives Anatomy Histology Embryology, Strasbourg, 14:167-203. GUIBE, J. 1970. L'apparil Digestif. Traite de Zoologie. Reptiles. Caracteres Generaux et Anatomie, 14:521- 548. HYMAN, L.H. 1942. Comparative vertebrate anatomy. Chicago: The University of Chicago Press. REESE, A.M. 191 0. Development of the digestive canal of the American alligator (Smithsonian Miscellaneous Collection, 56). STARCK, D. 1955. Embryologie. Stuttgart: Georg Thieme Verlag. STIDWORTHY, J. 1971 . Snakes of the world. New York: Grosset & Dunlop. VORSTMAN, A. G. 1939. Die Lage des Fettkbrpers der Krokodile und seine Entwicklung. Zoologischer Anzeiger, 126: 185- 191. 

The topography of the thoracic and abdominal organs of the Nile crocodile (Crocodylus niloticus)

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The topography of the thoracic and abdominal organs of the Nile crocodile (Crocodylus niloticus)

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