胎儿股骨滋养管方向的形成

DETERMINATION OF THE DIRECTION OF THE NUTRIENT A RTERIES OF THE FEMUR IN THE HUMAN FETUS

用X线摄片结合解剖方法研究了自三个月至出生前共40例胎儿80根股骨的滋养动脉。胎儿的滋养动脉相对较粗,数量显著较成人的多,有两支以上的占86.25%。其中上滋养动脉行向下,穿过骨质形成下行的滋养管,进入髓腔后再转折向上,分布到股骨的上端;下滋养动脉与之相反,形成上行的滋养管,入髓腔后转而向下,分布于股骨的下端。滋养孔在股骨纵向上的分布(孔指数)与成人极为近似,这说明股骨滋养孔的相对位置从胎儿直到成年是保持恒定的。我们未能证实胎儿滋养动脉都呈直角进入骨干。作者认为,骨膜学说、肌肉学说或血管学说都以滋养动脉最初呈直角进入骨干为前提可能还缺少足够的根据。股骨滋养孔最初就是两向的,成人股骨异向的滋养孔是胚胎时期上滋养动脉的残留。作者推测胚胎时期的上滋养动脉可能有一部分在生后退化、消失,而另一部分可能在生后发生了方向的转变,由下行而转为上行。

Forty human fetuses ranging from C-R length 72 mm(which corresponds to a developmental stage of the second week in the third month of the embryo)to fullterm were used to investigate the nutrient arteries of the femora using the dissection method and roentgenography.In comparison with adults,there are apparently more(P<0.01)nutrient arteries in the femora of fetus,and they are relatively larger in size.Of all the 80 femora examined,86.25%have at least two arteries in each bone.Among them,the upper nutrient artery passes downward,entering the cortex of the diaphysis and running into a canal which orients towards the distal end of the femur.After reaching the medullary cavity,the upper nutrient artery changes its direction and turns upward,supplying the proximal end of the femur.The lower nutrient artery on the contrary passes first upward,then into a canal in the bone cortex with an upward direction.After reaching the medullary cavity,it turns downward and distributes over the distal end of the femur.The distribution of the nutrient foramina which scatter along the longitudinal aspect of the bone("foramen index")is very much similar to those of the adults,this finding indicates that the relative position of the nutrient foramina remains constant in the developmental process and in postnatal growth.In the d.evelopmental stage from C-R 72 mm to full-term,there is no evidence to confirm that all the nutrient arteries enter into the long bones at a right angle.The authors noted that the theory of periosteum,of muscle,and of blood vessel are all based on the prerequisite that at the very beginning of the development the nutrient arteries all enter into the long bones at a right angle,but it seems to the authors that they are not supported by the findings presented here.In the authors’opinion,at the very beginning of development,the nutrient arteries of the femur really enter contrarily into the shaft of the long bones.The anomalously directed foramen occasionally found in adults is a rudiment of the canal of the upper nutrient artery of the fetus.Hence,it is suggested that some of the upper nutrient arteries of the fetus may degenerate and disappear gradually after birth,and the others may change their direction from downward to upward during the period of postnatal growth due to a functional transition.