. Chordate morphology. Morphology (Animals); Chordata. efferent vein afferent renol channels hole in valve diaphragm external iliac efferent of onterior lobe ischioc coccygeomesenteric renal portal channel. external iliac afferent of posterior lobules efferent of posterior lobules -hypogastric vein -caudal vein B Figure 11-38. The renal porfal system of the bird. A, with details of the valve between the external iliac and the efferent renal channel. The arrows in A indicate the direction of flow. (After Spanner, 1925) the posterior vena caval stem. In the frog, only the post- caval stem is inv
. Chordate morphology. Morphology (Animals); Chordata. efferent vein afferent renol channels hole in valve diaphragm external iliac efferent of onterior lobe ischioc coccygeomesenteric renal portal channel. external iliac afferent of posterior lobules efferent of posterior lobules -hypogastric vein -caudal vein B Figure 11-38. The renal porfal system of the bird. A, with details of the valve between the external iliac and the efferent renal channel. The arrows in A indicate the direction of flow. (After Spanner, 1925) the posterior vena caval stem. In the frog, only the post- caval stem is involved in this drainage. In the development of the postcardinal drainage of the anuran (Figure 11-39), lateral (postcardinal) and medial (subcardinal) channels of a reticulum enclosing the nephric duct are seen. The medial (subcardinal) channel appears first (10-mm frog). The postcaval stem connects with the right postcardinal. Both postcardinals flow through pro- nephric sinuses to reach the duct of Cuvier (Figure 11-39); these sinuses are eliminated with the loss of the pronephros. The same general pattern appears to hold for the sala- manders. Choonafe fishes Prolopterus, described by Parker, has lost the right connection with the duct of Cuvier; this is re- placed by a postcaval stem. The posterior parts of both postcardinals form renal portal vessels which drain the pelvic and caudal veins. Subcardinal channels, interconnected by cross channels, drain the kidneys. The postcava enters the liver and receives the hepatic veins along its course. The hepatic portal system drains the intestine by way of in- traintestinal and subintestinal channels. In Neoceralodus the picture differs in that the caudal vein flows into the postcava rather than the renal portal veins. In addition, there are both ventral abdominal and lateral cu- taneous veins, connected with the renal portal and caudal veins respectively. The development of the circulatory channels oiNeoceralo- dus has been describ
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