. Chordate morphology. Morphology (Animals); Chordata. two stems. In the placental, the left duct of Cuvier (common cardinal) is retained as the coronary sinus of the heart. Reptiles The head drainage pattern of the reptile is much the same as that of the mammal (Figure 1 1-29). The inter- nal jugular vein gives off a branch, the inferior jugular, to the musculature of the throat; it then passes up behind and over the tympanic cavity. Here it receives a posterior cere- bral branch which passes through the vagus (jugular) fora- men. This posterior cerebral stem is connected by a sigmoid sinus w
. Chordate morphology. Morphology (Animals); Chordata. two stems. In the placental, the left duct of Cuvier (common cardinal) is retained as the coronary sinus of the heart. Reptiles The head drainage pattern of the reptile is much the same as that of the mammal (Figure 1 1-29). The inter- nal jugular vein gives off a branch, the inferior jugular, to the musculature of the throat; it then passes up behind and over the tympanic cavity. Here it receives a posterior cere- bral branch which passes through the vagus (jugular) fora- men. This posterior cerebral stem is connected by a sigmoid sinus with the middle cerebral vessel, which in part forms the transverse sinus. The main lateral head vein passes for- ward from the posterior cerebral stem, over the columella, receives the middle cerebral vein emerging from the trigem- inal notch, and goes forward into the orbit and the orbital sinus. Between the orbital sinus and middle cerebral branch, the lateral head veins are interconnected through the basis cranii below the dorsum sellae. The orbital sinuses are also interconnected through the interorbital septum. Branches from the orbital sinus serve the temporal region and extend into the maxilla, passing forward through the alveolar passage of that bone. There is also a pterygoid vein, which in the roof of the mouth gives off a palatine division. Anteriorly the orbital sinus connects through the orbitonasal fissure with the nasal sinus; the nasal sinus is connected also with the maxillary vein. The brain is largely drained by a dorsal sagittal sinus which leads into transverse sinuses. The middle cerebral stem may exit behind the trigeminal (Sphenodon) or in front of (and over) that root (Lacerta and turtle). In some lizards and in crocodiles, the posterior cerebral stem is re- placed by another passing out through the foramen magnum. The alligator lacks the middle cerebral connection. The turtle has all of these stems. In the reptile a vena capitis medialis is only slight
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