[A metrical study of the aorta and main aortic branches in the human fetus].

There have been some metrical studies on the aorta of human adults. However, little work has been done on Japanese fetuses. This study was carried out to investigate such arterial changes during the fetal age period of 6-8 months as 1. lengths of the aortic arch, thoracic aorta and abdominal aorta, 2. relative positions on the aorta where main aortic branches arise, and 3. diameters of the main aortic branches. The results were as follows: 1) The total length of the aorta increased with fetal age. Growth rates of the aortic subdivisions were different from one another. During the 6-7 month period, proportions of the aortic arch and the abdominal aorta to the whole aorta increased. On the other hand, the proportion of the thoracic aorta decreased during this period. During the 7-8 month period, the proportions of each subdivision were unchanged. 2) Diameters of the main aortic branches and distances between these branches and the brachiocephalic artery were measured. During the 6-7 month period, the relative positions of arteries arising from the aortic arch moved toward the heart along the aorta, while the celiac artery, superior mesenteric artery and renal artery moved downward. The relative positions of the ductus arteriosus and the inferior mesenteric artery remained unchanged during the period. No change was seen in the relative positions during the 7-8 month period. 3) Distances between the arising points of the left and right intercostal arteries were measured on the dorsal surface of the thoracic aorta. The distance was wider in the upper segment of the aorta than in the lower segments.(ABSTRACT TRUNCATED AT 250 WORDS)