The venous system of the proventriculus of duck (Anas domesticus)

The proventriculus of duck is lacking in the V. proventricularis dextra and V. proventriculolienalis both of which are present in the chicken. In it the V. lienalis empties directly into the V. portae hepatis dextra. Therefore, most of the blood from the proventriculus of duck is drained by the well-developed V. proventricularis cranialis and empties into the V. cava cranialis sinistra without showing any morphological relation to the portal vein. A small amount of the remaining venous blood is drained by the portal vein after passing through the V. proventricularis sinistra; that is, most of the venous blood in the proventriculus of duck empties into the systemic circulation. In the wall of the proventriculus of duck there is a dense venous network formed by anastomosis between V. proventricularis cranialis and V. proventricularis sinistra. The systemic circulation is connected directly with the portal circulation by this anastomosis. Such a close connection between the systemic and portal circulations and the distribution of venous blood from the proventriculus appear to be a noticeable problem in birds in association with phylogenetics and food habits. Although the principle for the terminology of the venous system in the avian proventriculus was proposed by the authors, further experiments and discussion will be required for a uniformity of the nomecnlature in the future.