在“脊髓和脊神经”一节的教学中,不少学生认为,脊髓下端既然“与第一腰椎下缘平齐”,怎还有31对脊神经?以致疑惑不解。对此知识点应予弄清。 脊髓外观是一完整体,但可籍每对脊神经根的范围划分31节段,即8个颈节、12个胸节、5个腰节、5个骶节、1个尾节。在胆胎三个月以前,脊髓与脊柱长度相等,所有的脊神经根均呈水平方向自脊髓发出进入相当的椎间孔。从胚胎第4个月起,脊髓增长速度比脊柱增长速度缓慢,由于脊髓上端连于脑而固定,因此脊髓上段与脊柱的局部关系变化很小,而脊髓的中、下部各节渐高于相应椎骨。新生儿脊髓下端平齐第3腰椎,成人则达第1腰椎下缘。因此,腰、骶、尾部的神经根在未出相应椎间孔前,有一长段在椎管内斜向下行,它们围绕终然形成马尾,并浸浴于脑脊液中。虽在成人一般第1腰椎 In the teaching of “spinal cord and spinal nerves”, many students believe that since the lower end of the spinal cord “is flush with the lower edge of the first lumbar spine”, there are still 31 pairs of spinal nerves that cause confusion. This knowledge should be clarified. The appearance of the spinal cord is a complete body, but it can be divided into 31 segments for each pair of spinal nerve roots, ie, 8 cervical segments, 12 thoracic segments, 5 lumbar segments, 5 temporal segments, and 1 tail segment. Three months before the gallbladder, the length of the spinal cord and the spine were equal, and all the spinal nerve roots were horizontally emitted from the spinal cord into a comparable intervertebral foramina. From the 4th month onwards, the growth rate of the spinal cord is slower than that of the spine. Since the upper end of the spinal cord is fixed on the brain, the local relationship between the upper part of the spinal cord and the spine changes little, while the middle and lower sections of the spinal cord gradually increase vertebra. The neonatal spinal cord is flush with the third lumbar spine, while adults reach the lower lumbar spine. Therefore, the nerve roots of the lumbar, iliac, and caudal pedicles have a long section that descends obliquely in the spinal canal before they exit the corresponding intervertebral foramen. They form a cauda equina around and are bathed in cerebrospinal fluid. Although in the general adult first lumbar vertebrae