Veins of the lumbar spinal @entity21 in XXXX adults and fetuses.

@entity1 @entity1457 @entity4494 @entity21
To obtain a fundamental knowledge of the morphological relationship between nerve root symptoms and @entity1457 , the distribution pattern of the veins in the lumbar spinal @entity21 from the first to fifth vertebrae was investigated in 5 adult @entity1 cadavers (mean age 69.6 years) and 5 @entity1 fetuses (mean age 6.6 months). The following results were obtained: 1) In the adults the veins perforating from the outer surface of the fifth lumbar spinal @entity4494 were smaller in number than those perforating from the first to fourth @entity21 . In contrast, in the fetuses the number of such veins was increased in the lower lumbar spinal @entity21 . In each of the @entity21 , the number of veins emerging through the dorsal side was much higher than the number perforating from the outer surface of the ventral sides. The veins perforating through the outer surface of the @entity4494 formed weak venous networks (periganglionic venous plexus) surrounding the dorsal ramus of the spinal nerve. 2) The veins communicating with the tributaries from the periganglionic venous plexus were classified into three types. Type 1 veins flowed into the intervertebral veins (the frequency ranged from 9.2 to 18.2 in the adults and from 22.4 to 37.0 in the fetuses). Type 2 veins coursed in the spinal cord along the dorsal root fibers and penetrated the dura mater on the way (the frequency ranged from 0.4 to 4.8 in the adults and from 1.2 to 2.2 in the fetuses). Type 3 veins opened directly into the internal vertebral plexus (the frequency ranged from 0.4 to 1.8 in the adults and from 0 to 0.4 in the fetuses). Type 1 veins were the most frequent among the three types of veins in both adults and fetuses. Few type 3 veins were observed in either group. 3) In the first and second lumbar vertebrae in the adults, three-quarters of each spinal @entity4494 was situated in the vertebral canal. In the lower lumbar region (L3-L5), three quarters of each spinal @entity4494 lay on the outside of the vertebral canal. In the fetuses, approximately one half to three-quarters of each lumbar spinal @entity4494 was located in the vertebral canal.
