No abstract
The objective of this report is to present a standardized nomenclature system for radiographic projections used in veterinary medicine that is anatomically accurate, easily understood, and easily communicated. The system is based on two simple rules: (1) radiographic projections should be named using only proper veterinary anatomic directional terms or their abbrecviations; (2) radiographic projections should be described by the direction that the central ray of the primary x‐ray beam penetrates the body part of interest, from point of entrance to point of exit. Additional recommendations are included that will result in further standardization of the nomenclature. These include supplemental guidelines for (1) combination of terms; (2) angles of obliquity; (3) positions of the body; and (4) orientation of the central ray relative to space. In addition, the position of joints and other body parts may require description. Selected examples of how the nomenclature system can be applied are included. It is recommended that this nomenclature be required by editors of veterinary journals and textbooks.
The rete mirabile cerebri and the hypophysial vascularization were studied by various injection and staining techniques. The rostral hypophysial arteries arose bilaterally from the arterial circle of the cerebrum, while the caudal hypophysial arteries arose from the rete miabile on the dosal and caudal surfaces of the gland. The ramifications of the rostral hypophysial arteries supplied the vascular structures in the hypophysial stalk, which were classified on the basis of their structure into three groups; arboriza tion forms, spike forms, and capillary loops. These structures drained into large portal vessels leading to the pars distalis. The pars distalis received a second smaller group of portal vessels from the capillary bed of the lower infundibular stem. The small group of portal vessels was limited in its extent by a well-developed hypophysial cleft. No direct arterial supply to the pars distalis could be demonstrated. The findings of this study support the view that the blood in the hypophysial portal system flows distally from the hypophysial stalk to the pars distalis.Evidence strongly suggests that the hypophysial portal system forms a route for hypothalamic control over pituitary function (Harris, '55; Greep, '63). Direct neural control of anterior lobe secretion in the ox seems unlikely since Gilmore, Peterson, and Rasmussen ('41) were unable to find nerve fibers in the pars distalis. The original description of the hypophysial portal system in man by Popa and Fielding ('30) was followed by studies of pituitary circulation in many species (Romeis, '40; Diepen, '62). The existence of a portal system and its functional implications have stimulated interest in the study of hypophysial vascularization.The arterial supply to the bovine hypophysis arises from the rete mirable cerebri. This extensive arterial plexus which surrounds the pituitary has perplexed anatomists since the time of Galen.Ask-Upmark ('35 > reviewed the early theories on the physiologic significance of the rete. He postulated that the rete may operate mechanically in maintaining cerebral arterial pressure at a convenient and constant level. Zhedenov ('37) described the pre-and postnai:al formation of the rete and the regression of the internal carotid artery in the ox. He believed that the rete functioned a s a regulating reservoir. Legait ('44) reported highly innervated arteriovenous anastomoses between the arterioles of the re te and the cavernous sinus in the calf. These anastomoses were AM. J. ANAT., 116: 91-114.
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