308 GLOSSARY OF EMBRYOLOGICAL TERMS 



Vena Cava Posterior — single median ventral vein which represents rem- 

 nant of anterior right cardinal and which later receives hepatic vein 

 prior to joining ductus Cuvieri, and later joins right auricle directly. 



Ventral — belly surface. Ventrad means toward belly surface. 



Ventral Mesentery — double layer of mesoblast which connects alimentary 

 canal with splanchnopleure in embryo. 



Ventricle III — main cavity (diocoel) of forebrain, related to paired lateral 

 ventricles or telocoels, by way of foramina of Monro. 



Ventricle IV — main cavity of hindbrain (rhombencephalon) connected 

 anteriorly with aqueduct of Sylvius and posteriorly with neural canal, 

 having as a roof the vascular posterior choroid plexus. 



Ventricle, Lateral — See Lateral Ventricles of the Brain. 



Ventricle of the Heart — chamber of the heart, single in frog and very mus- 

 cular, developing from anterior myocardium and provided with valves; 

 connected with bulbus arteriosus anteriorly. 



Vertebra — derivatives of sclerotome which surround nerve cord and noto- 

 chord, and finally incorporate notochord by chondrification and 

 ossification (centrum). 



Vertebral Arch — See Neural Arch. 



Vertebral Plate — See Axial Mesoderm. (Syn., segmental plate.) 



Vesicle, Germinal — nucleus of egg while it is a distinct entity and before 

 elimination of either of the polar bodies. 



Visceral — pertaining to viscera. 



Visceral Arches — mesodermal masses (usually six pairs) between visceral 

 pouches and lateral to pharynx of all vertebrate embryos, including 

 mandibular, hyoid, and four branchial arches. Each arch is bounded 

 by endoderm on pharyngeal side and ectoderm on outside. (Syn,, 

 visceral arches III to VI are also called branchial arches I to IV, 

 respectively; pharyngeal arch.) 



Visceral Clefts — slit-like openings between pharynx and outside, found in 

 vertebrate embryos on either side of visceral arches II to V, or less, 

 consisting of peripheral lining of ectoderm and mesial lining of 

 endoderm. (Syn., pharyngeal, and some may be called gill or branchial 

 clefts.) 



Visceral Furrow — ectodermal invaginations which may meet endodermal 

 pharyngeal evaginations to form visceral clefts. (Syn., visceral groove.) 



Visceral Groove — See Visceral Furrow. 



