efferent artery 



afferent artery 



efferent artery 

 afferent artery 



gill ray 



septum 



gill raker 



B ACIPENSER D TELEOST 



Figure 11-19. Interrelationships of vessels in the gill and as seen in 

 semidiogrammatic anterior view, A and C, and in cross section, B and 

 D. (After Goodrich, 1930) 



the interior opening of the gill pouches, and send vessels to 

 the posterior and anterior hemibranchs of adjacent pouches. 

 The efferent arteries draining adjacent hemibranchs are in- 

 terconnected. 



The hyoid afferent serves only a posterior hemibranch. 

 The hyoid efferent extends dorsally to the region of the h)'po- 

 physes where it joins the carotid stem. The external carotid 

 arises directly from the efferent of the second branchial 

 arch but receives contributions from the efferents of the 

 first branchial arch. 



In development, the first aortic arch is the mandibular 

 which appears at a stage of 40 somites. By 70 somites the 

 mandibular arch is reduced in size and three other arches 

 have appeared. The mandibular arch has lost its connection 

 with the ventral aorta in an embryo of 4.5 mm; this velar 

 artery persists into the adult but along with its large post- 

 orbital branch forms a part of the external carotid system. 

 By 6 mm the arches have divided into an outer afferent and 

 an inner efferent division. This relationship is not found in 

 the adult, where both afferent and efferent vessels lie medial 

 to the pouch. These vessels extend to the region of the in- 

 ternal branchial opening and there divide into dorsally, 

 laterally, and ventrally extending branches. Their branches 



orbital artery 



cerebral artery , 



basilar artery 

 '\ J^=!- coeliaco-mesenteric artery 



12 3 4 5 6 



optic artery, 

 ophthalmic artery 



supraorbital 



infraorbital and 

 sphenopalatine 



mandibular artery 

 afferent pseudobra 



hypobranchiol artery 



cardiac artery 



Figure 1 1-20. Five stages in the development of the aortic orches of the shark. (After Goodrich, 

 1930) 



352 



THE CIRCULATORY SYSTEM 



